This work was supported by JSPS KAKENHI Grant Numbers JP24750023, JP24350012, MEXT KAKENHI Grant Numbers JP26104534, JP16H00850, JP26102541, JP16H00782, and MEXT-Supported Program for the Strategic Research Foundation at Private Universities, 2015&#8211;2019.

<ol>
	<li>Pol&#237;vka, T., Herek, J. L., Zigmantas, D., &#197;kerlund, H. -. E., Sundstr&#246;m, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct+Observation+of+the+(Forbidden)+S1+State+in+Carotenoids.">Direct Observation of the (Forbidden) S1 State in Carotenoids.</a> Proceedings of the National Academy of Sciences of the United States of America. 96 (9), 4914-4917 (1999).</li><li>Takaya, T., Iwata, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Relaxation+Mechanism+of+&#946;-Carotene+from+S2+(1Bu+)+State+to+S1+(2Ag-)+State:+Femtosecond+Time-Resolved+Near-IR+Absorption+and+Stimulated+Resonance+Raman+Studies+in+900-1550+nm+Region.">Relaxation Mechanism of &#946;-Carotene from S2 (1Bu+) State to S1 (2Ag-) State: Femtosecond Time-Resolved Near-IR Absorption and Stimulated Resonance Raman Studies in 900-1550 nm Region.</a> Journal of Physical Chemistry A. 118 (23), 4071-4078 (2014).</li><li>Takaya, T., Anan, M., Iwata, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vibrational+Relaxation+Dynamics+of+&#946;-Carotene+and+Its+Derivatives+with+Substituents+on+Terminal+Rings+in+Electronically+Excited+States+as+Studied+by+Femtosecond+Time-Resolved+Stimulated+Raman+Spectroscopy+in+the+Near-IR+Region.">Vibrational Relaxation Dynamics of &#946;-Carotene and Its Derivatives with Substituents on Terminal Rings in Electronically Excited States as Studied by Femtosecond Time-Resolved Stimulated Raman Spectroscopy in the Near-IR Region.</a> Physical Chemistry Chemical Physics. 20 (5), 3320-3327 (2017).</li><li>Guo, J., Ohkita, H., Benten, H., Ito, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Near-IR+Femtosecond+Transient+Absorption+Spectroscopy+of+Ultrafast+Polaron+and+Triplet+Exciton+Formation+in+Polythiophene+Films+with+Different+Regioregularities.">Near-IR Femtosecond Transient Absorption Spectroscopy of Ultrafast Polaron and Triplet Exciton Formation in Polythiophene Films with Different Regioregularities.</a> Journal of the American Chemical Society. 131 (46), (2009).</li><li>Hwang, I. -. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Carrier+Generation+and+Transport+in+Bulk+Heterojunction+Films+Processed+with+1,8-Octanedithiol+as+a+Processing+Additive.">Carrier Generation and Transport in Bulk Heterojunction Films Processed with 1,8-Octanedithiol as a Processing Additive.</a> Journal of Applied Physics. 104 (3), 033706 (2008).</li><li>Yonezawa, K., Kamioka, H., Yasuda, T., Han, L., Moritomo, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fast+Carrier+Formation+from+Acceptor+Exciton+in+Low-Gap+Organic+Photovoltaic.">Fast Carrier Formation from Acceptor Exciton in Low-Gap Organic Photovoltaic.</a> Applied Physics Express. 5 (4), 042302 (2012).</li><li>Takaya, T., Enokida, I., Furukawa, Y., Iwata, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct+Observation+of+Structure+and+Dynamics+of+Photogenerated+Charge+Carriers+in+Poly(3-hexylthiophene)+Films+by+Femtosecond+Time-Resolved+Near-IR+Inverse+Raman+Spectroscopy.">Direct Observation of Structure and Dynamics of Photogenerated Charge Carriers in Poly(3-hexylthiophene) Films by Femtosecond Time-Resolved Near-IR Inverse Raman Spectroscopy.</a> Molecules. 24 (3), 431 (2019).</li><li>Clafton, S. N., Huang, D. M., Massey, W. R., Kee, T. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Femtosecond+Dynamics+of+Excitons+and+Hole-Polarons+in+Composite+P3HT/PCBM+Nanoparticles.">Femtosecond Dynamics of Excitons and Hole-Polarons in Composite P3HT/PCBM Nanoparticles.</a> Journal of Physical Chemistry B. 117 (16), 4626-4633 (2013).</li><li>Cook, S., Furube, A., Katoh, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+the+Excited+States+of+Regioregular+Polythiophene+P3HT.">Analysis of the Excited States of Regioregular Polythiophene P3HT.</a> Energy &amp; Environmental Science. 1 (2), 294-299 (2008).</li><li>Okino, S., Takaya, T., Iwata, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Femtosecond+Time-Resolved+Near-Infrared+Spectroscopy+of+Oligothiophenes+and+Polythiophene:+Energy+Location+and+Effective+Conjugation+Length+of+Their+Low-Lying+Excited+States.">Femtosecond Time-Resolved Near-Infrared Spectroscopy of Oligothiophenes and Polythiophene: Energy Location and Effective Conjugation Length of Their Low-Lying Excited States.</a> Chemistry Letters. 44 (8), 1059-1061 (2015).</li><li>Takaya, T., Iwata, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+Femtosecond+Time-Resolved+Near-IR+Multiplex+Stimulated+Raman+Spectrometer+in+Resonance+with+Transitions+in+the+900-1550+nm+Region.">Development of a Femtosecond Time-Resolved Near-IR Multiplex Stimulated Raman Spectrometer in Resonance with Transitions in the 900-1550 nm Region.</a> Analyst. 141 (14), 4283-4292 (2016).</li><li>Jas, G. 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W., Kukura, P., Mathies, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Femtosecond+Broadband+Stimulated+Raman:+A+New+Approach+for+High-Performance+Vibrational+Spectroscopy.">Femtosecond Broadband Stimulated Raman: A New Approach for High-Performance Vibrational Spectroscopy.</a> Applied Spectroscopy. 57 (11), 1317-1323 (2003).</li><li>McCamant, D. W., Kukura, P., Yoon, S., Mathies, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Femtosecond+Broadband+Stimulated+Raman+Spectroscopy:+Apparatus+and+Methods.">Femtosecond Broadband Stimulated Raman Spectroscopy: Apparatus and Methods.</a> Review of Scientific Instruments. 75 (11), 4971-4980 (2004).</li><li>Kukura, P., McCamant, D. W., Mathies, R. 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The authors have nothing to disclose.

Crucial factors in femtosecond time-resolved near-IR multiplex stimulated Raman measurement 
To obtain time-resolved near-IR stimulated Raman spectra with a high signal-to-noise ratio, the probe spectrum should ideally have uniform intensity in the whole wavelength range. White-light continuum generation (section 2.5) is, therefore, one of the most crucial parts of time-resolved near-IR stimulated Raman experiments. In general, the probe spectrum becomes broad and flat as the intensity of the incide...

Raman spectroscopy is a powerful and versatile tool for investigating the structures of molecules in a wide variety of samples from simple gases, liquids, and solids to functional materials and biological systems. Raman scattering is significantly enhanced when the photon energy of the excitation light coincides with the electronic transition energy of a molecule. The resonance Raman effect enables us to selectively observe the Raman spectrum of a species in a sample composed of many kinds of molecules. Near-IR electronic transitions are drawing a lot of attention as a probe for investigating the excited-state dynamics of molecules with large &#960;-conjugated structures. The energy and lifetime of the lowest excited singlet state have been determined for several carotenoids, which have a long one-dimensional polyene chain1,2,3. The dynamics of neutral and charged excitations have been extensively investigated for various photoconductive polymers in films4,5,6,7, nanoparticles8, and solutions9,10,11. Detailed information on the structures of the transients will be obtainable if time-resolved near-IR Raman spectroscopy is applied to these systems. Only a few studies, however, have been reported on time-resolved near-IR Raman spectroscopy12,13,14,15,16, because the sensitivity of near-IR Raman spectrometers is extremely low. The low sensitivity principally originates from the low probability of near-IR Raman scattering. The probability of spontaneous Raman scattering is proportional to &#969;i&#969;s3, where &#969;i and &#969;s are the frequencies of the excitation light and the Raman scattering light, respectively. In addition, commercially available near-IR detectors have much lower sensitivity than CCD detectors functioning in the UV and visible regions.
Femtosecond time-resolved stimulated Raman spectroscopy has emerged as a new method of observing time-dependent changes of Raman active vibrational bands beyond the apparent Fourier-transform limit of a laser pulse17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33. Stimulated Raman scattering is generated by irradiation of two laser pulses: the Raman pump and probe pulses. Here it is assumed that the Raman pump pulse has a larger frequency than the probe pulse. When the difference between the frequencies of the Raman pump and probe pulses coincides with the frequency of a Raman active molecular vibration, the vibration is coherently excited for a large number of molecules in the irradiated volume. Nonlinear polarization induced by the coherent molecular vibration enhances the electric field of the probe pulse. This technique is particularly powerful for near-IR Raman spectroscopy, because stimulated Raman scattering can solve the problem of the sensitivity of time-resolved near-IR spontaneous Raman spectrometers. Stimulated Raman scattering is detected as intensity changes of the probe pulse. Even if a near-IR detector has a low sensitivity, stimulated Raman scattering will be detected when the probe intensity is sufficiently increased. The probability of stimulated Raman scattering is proportional to &#969;RP&#969;SRS, where &#969;RP and &#969;SRS are the frequencies of the Raman pump pulse and stimulated Raman scattering, respectively20. The frequencies for stimulated Raman scattering, &#969;RP and &#969;SRS, are equivalent to &#969;i and &#969;s for spontaneous Raman scattering, respectively. We have recently developed a femtosecond time-resolved near-IR Raman spectrometer using stimulated Raman scattering for investigating the structures and dynamics of short-lived transients photogenerated in &#960;-conjugate systems2,3,7,10. In this article, we present the technical details of our femtosecond time-resolved near-IR multiplex stimulated Raman spectrometer. Optical alignment, acquisition of time-resolved stimulated Raman spectra, and calibration and correction of recorded spectra are described. The excited-state dynamics of &#946;-carotene in toluene solution is studied as a representative application of the spectrometer.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>1-Axis Translational Stage</td>
			<td>OptSigma</td>
			<td>TSD-401S</td>
			<td>Products equivalent to this are used as well; for M22, L9, and CM in Figure 1A</td>
		</tr>
		<tr>
			<td>20-cm Optical Delay Line</td>
			<td>OptSigma</td>
			<td>SGSP26-200</td>
			<td>ODL1 in Figure 1A</td>
		</tr>
		<tr>
			<td>3-Axis Translational Stage</td>
			<td>OptSigma</td>
			<td>TSD-405SL</td>
			<td>For L8 in Figure 1A</td>
		</tr>
		<tr>
			<td>3-Axis Translational Stage</td>
			<td>Suruga Seiki</td>
			<td>B72-40C</td>
			<td>For FC in Figure 1A</td>
		</tr>
		<tr>
			<td>5-cm Optical Delay Line</td>
			<td>PMT</td>
			<td>HRS-0050</td>
			<td>ODL2 in Figure 1A</td>
		</tr>
		<tr>
			<td>Al Concave Mirror</td>
			<td>Thorlabs</td>
			<td>CM254-050-G01</td>
			<td>Focal length: 50 mm; CM in Figure 1A</td>
		</tr>
		<tr>
			<td>Base Plate</td>
			<td>Suruga Seiki</td>
			<td>A21-6</td>
			<td>Products equivalent to this are used as well; for M1-M32, BS1-BS3, L1-L10, I1-I17, P1-P2, HWP1-3, F1-F3, VND1-VND2, OC, BPF, HS, BBO, SP, CM, and FC in Figure 1A</td>
		</tr>
		<tr>
			<td>BBO Crystal</td>
			<td>EKSMA Optics</td>
			<td>-</td>
			<td>Type 1, &#952; = 23.2 deg; BBO in Figure 1A</td>
		</tr>
		<tr>
			<td>BK7 Plano-Concave Lens</td>
			<td>OptSigma</td>
			<td>SLB-25.4-50NIR2</td>
			<td>Focal length: 50 mm; IR anti-reflection coating; L6 in Figure 1A</td>
		</tr>
		<tr>
			<td>BK7 Plano-Convex Lens</td>
			<td>OptSigma</td>
			<td>SLB-25.4-150PIR2</td>
			<td>Focal length: 150 mm; IR anti-reflection coating; L2, L3, L5 in Figure 1A</td>
		</tr>
		<tr>
			<td>BK7 Plano-Convex Lens</td>
			<td>OptSigma</td>
			<td>SLB-25.4-100PIR2</td>
			<td>Focal length: 100 mm; IR anti-reflection coating; L4 in Figure 1A</td>
		</tr>
		<tr>
			<td>BK7 Plano-Convex Lens</td>
			<td>OptSigma</td>
			<td>SLB-25.4-200PIR2</td>
			<td>Focal length: 200 mm; IR anti-reflection coating; L7 in Figure 1A</td>
		</tr>
		<tr>
			<td>Broadband Dielectric Mirror</td>
			<td>OptSigma</td>
			<td>TFMS-25.4C05-2/7</td>
			<td>M22-M25, M28, M29 in Figure 1A</td>
		</tr>
		<tr>
			<td>Broadband Dielectric Mirror</td>
			<td>Precision Photonics (Advanced Thin Films)</td>
			<td>-</td>
			<td>M26, M27, M30-M32 in Figure 1A</td>
		</tr>
		<tr>
			<td>Broadband Half-Wave Plate</td>
			<td>CryLight</td>
			<td>-</td>
			<td>HWP3 in Figure 1A</td>
		</tr>
		<tr>
			<td>Color Glass Filter</td>
			<td>HOYA</td>
			<td>IR85</td>
			<td>F1 in Figure 1A</td>
		</tr>
		<tr>
			<td>Color Glass Filter</td>
			<td>HOYA</td>
			<td>RM100</td>
			<td>F2 in Figure 1A</td>
		</tr>
		<tr>
			<td>Color Glass Filter</td>
			<td>Schott</td>
			<td>BG39</td>
			<td>F3 in Figure 1A</td>
		</tr>
		<tr>
			<td>Computer</td>
			<td>Dell</td>
			<td>Vostro 200 Mini Tower</td>
			<td>OS: Windows XP</td>
		</tr>
		<tr>
			<td>Cyclohexane</td>
			<td>Kanto Kagaku</td>
			<td>07547-1B</td>
			<td>HPLC grade</td>
		</tr>
		<tr>
			<td>Data Analysis Software</td>
			<td>Wavemetrics</td>
			<td>Igor Pro 8</td>
			<td></td>
		</tr>
		<tr>
			<td>Dielectric Beamsplitter</td>
			<td>LAYERTEC</td>
			<td>-</td>
			<td>Reflection : Transmission = 2 : 1; BS1 in Figure 1A</td>
		</tr>
		<tr>
			<td>Dielectric Beamsplitter</td>
			<td>LAYERTEC</td>
			<td>-</td>
			<td>Reflection : Transmission = 1 : 1; BS2, BS3 in Figure 1A</td>
		</tr>
		<tr>
			<td>Dielectric Mirror</td>
			<td>Precision Photonics 
			(Advanced Thin Films)</td>
			<td>-</td>
			<td>M1-M8 in Figure 1A</td>
		</tr>
		<tr>
			<td>Digital Oscilloscope</td>
			<td>Tektronix</td>
			<td>TDS3054B</td>
			<td>500 MHz, 5 GS/s</td>
		</tr>
		<tr>
			<td>Elastomer Tube</td>
			<td>-</td>
			<td>-</td>
			<td>Figure 1E</td>
		</tr>
		<tr>
			<td>Femtosecond Ti:sapphire Oscillator</td>
			<td>Coherent</td>
			<td>Vitesse 800-2</td>
			<td>Wavelength: 800 nm, pulse duration: 100 fs, average power: 280 mW, repetition rate: 80 MHz; included in Ti:S in Figure 1A</td>
		</tr>
		<tr>
			<td>Femtosecond Ti:sapphire Regenerative Amplifier</td>
			<td>Coherent</td>
			<td>Legend-Elite-F-HE</td>
			<td>Wavelength: 800 nm, pulse duration: 100 fs, pulse energy: 3.5 mJ, repetition rate: 1 kHz; included in Ti:S in Figure 1A</td>
		</tr>
		<tr>
			<td>Film Polarizer</td>
			<td>OptSigma</td>
			<td>SPFN-30C-26</td>
			<td>P1 in Figure 1A</td>
		</tr>
		<tr>
			<td>Glan-Taylor Prism</td>
			<td>OptSigma</td>
			<td>GYPB-10-10SN-3/7</td>
			<td>P2 in Figure 1A</td>
		</tr>
		<tr>
			<td>Gold Mirror</td>
			<td>OptSigma</td>
			<td>TFG-25C05-10</td>
			<td>M9-M21 in Figure 1A</td>
		</tr>
		<tr>
			<td>Half-Wave Plate</td>
			<td>OptSigma</td>
			<td>WPQ-7800-2M</td>
			<td>HWP1 in Figure 1A</td>
		</tr>
		<tr>
			<td>Harmonic Separator</td>
			<td>Coherent</td>
			<td>TOPAS-C HRs 410-540 nm</td>
			<td>HS in Figure 1A</td>
		</tr>
		<tr>
			<td>InGaAs Array Detector</td>
			<td>Horiba</td>
			<td>Symphony-IGA-512X1-50-1700-1LS</td>
			<td>512 ch, Liquid nitrogen cooled</td>
		</tr>
		<tr>
			<td>InGaAs PIN Photodiode</td>
			<td>Hamamatsu Photonics</td>
			<td>G10899-01K</td>
			<td></td>
		</tr>
		<tr>
			<td>IR Half-Wave Plate</td>
			<td>OptiSource</td>
			<td>-</td>
			<td>HWP2 in Figure 1A</td>
		</tr>
		<tr>
			<td>Iris</td>
			<td>Suruga Seiki</td>
			<td>F74-3N</td>
			<td>Products equivalent to this are used as well; I1-I17 in Figure 1A</td>
		</tr>
		<tr>
			<td>Lens Holder</td>
			<td>OptSigma</td>
			<td>LHF-25.4S</td>
			<td>Products equivalent to this are used as well; for L1-L10 in Figure 1A</td>
		</tr>
		<tr>
			<td>Magnetic Gear Pump</td>
			<td>Micropump</td>
			<td>184-415</td>
			<td></td>
		</tr>
		<tr>
			<td>Mirror Mount</td>
			<td>Siskiyou</td>
			<td>IM100.C2M6R</td>
			<td>Products equivalent to this are used as well; for M1-M32, BS1-BS3, BBO, CM in Figure 1A</td>
		</tr>
		<tr>
			<td>near-IR phosphor card</td>
			<td>Thorlabs</td>
			<td>VRC2</td>
			<td></td>
		</tr>
		<tr>
			<td>Nut</td>
			<td>-</td>
			<td>-</td>
			<td>Figure 1E, M4; purchased from a DIY store</td>
		</tr>
		<tr>
			<td>Optical Chopper</td>
			<td>New Focus</td>
			<td>3501</td>
			<td>OC in Figure 1A</td>
		</tr>
		<tr>
			<td>Optical Parametric Amplifier</td>
			<td>Coherent</td>
			<td>OPerA-F</td>
			<td>OPA1 in Figure 1A</td>
		</tr>
		<tr>
			<td>Optical Parametric Amplifier</td>
			<td>Coherent</td>
			<td>TOPAS-C</td>
			<td>OPA2 in Figure 1A</td>
		</tr>
		<tr>
			<td>Polarizer Holder</td>
			<td>OptSigma</td>
			<td>PH-30-ARS</td>
			<td>Products equivalent to this are used as well; for P1-P2 and HWP1-3 In Figure 1A</td>
		</tr>
		<tr>
			<td>Polyfluoroacetate Tube</td>
			<td>-</td>
			<td>-</td>
			<td>Figure 1E</td>
		</tr>
		<tr>
			<td>Post Holder</td>
			<td>OptSigma</td>
			<td>BRS-12-80</td>
			<td>Products equivalent to this are used as well; for M1-M32, BS1-BS3, L1-L10, I1-I17, P1-P2, HWP1-3, F1-F3, VND1-VND2, OC, BPF, HS, BBO, SP, CM, and FC in Figure 1A</td>
		</tr>
		<tr>
			<td>Quartz Flow Cell</td>
			<td>Tosoh Quartz</td>
			<td>T-70-UV-2</td>
			<td>FC in Figure 1A</td>
		</tr>
		<tr>
			<td>Quartz Plano-Concave Lens</td>
			<td>OptSigma</td>
			<td>SLSQ-25-50N</td>
			<td>Focal length: 50 mm; L8 in Figure 1A</td>
		</tr>
		<tr>
			<td>Quartz Plano-Convex Lens</td>
			<td>OptSigma</td>
			<td>SLSQ-25-100P</td>
			<td>Focal length: 100 mm; L1, L9 in Figure 1A</td>
		</tr>
		<tr>
			<td>Quartz Plano-Convex Lens</td>
			<td>OptSigma</td>
			<td>SLSQ-25-220P</td>
			<td>Focal length: 220 mm; L10 in Figure 1A</td>
		</tr>
		<tr>
			<td>Sapphire Plate</td>
			<td>Pier Optics</td>
			<td>-</td>
			<td>3 mm thick; SP in Figure 1A</td>
		</tr>
		<tr>
			<td>Si PIN Photodiode</td>
			<td>Hamamatsu Photonics</td>
			<td>S3883</td>
			<td></td>
		</tr>
		<tr>
			<td>Single Spectrograph</td>
			<td>Horiba Jobin Yvon</td>
			<td>iHR320</td>
			<td>Focal length: 32 cm</td>
		</tr>
		<tr>
			<td>Stainless Steel Rod</td>
			<td>Suruga Seiki</td>
			<td>A41-100</td>
			<td>Products equivalent to this are used as well; for M1-M32, BS1-BS3, L1-L10, I1-I17, P1-P2, HWP1-3, F1-F3, VND1-VND2, OC, BPF, HS, BBO, SP, CM, and FC in Figure 1A</td>
		</tr>
		<tr>
			<td>Stainless Steel Rod</td>
			<td>Newport</td>
			<td>J-SP-2</td>
			<td>Figure 1E</td>
		</tr>
		<tr>
			<td>Toluene</td>
			<td>Kanto Kagaku</td>
			<td>40180-1B</td>
			<td>HPLC grade</td>
		</tr>
		<tr>
			<td>U-Shaped Steel Plate</td>
			<td>-</td>
			<td>-</td>
			<td>Figure 1E; purchased from a DIY store</td>
		</tr>
		<tr>
			<td>Variable Neutral Density Filter (with a holder)</td>
			<td>OptSigma</td>
			<td>NDHN-100</td>
			<td>VND1 in Figure 1A</td>
		</tr>
		<tr>
			<td>Variable Neutral Density Filter (with a holder)</td>
			<td>OptSigma</td>
			<td>NDHN-U100</td>
			<td>VND2 in Figure 1A</td>
		</tr>
		<tr>
			<td>Visual Programming Language</td>
			<td>National Instruments</td>
			<td>LabVIEW 2009</td>
			<td>The control software in this study is programmed in LabVIEW 2009</td>
		</tr>
		<tr>
			<td>Volume-Grating Bandpass Filter</td>
			<td>OptiGrate</td>
			<td>BPF-1190</td>
			<td>BPF in Figure 1A</td>
		</tr>
		<tr>
			<td>&#946;-Carotene</td>
			<td>Wako Pure Chemical Industries</td>
			<td>035-05531</td>
			<td></td>
		</tr>
	</tbody>
</table>

ultrafast time-resolved near-ir stimulated raman measurements of functional &#960;-conjugate systems

Femtosecond time-resolved stimulated Raman spectroscopy is a promising method of observing the structural dynamics of short-lived transients with near infrared (near-IR) transitions, because it can overcome the low sensitivity of spontaneous Raman spectrometers in the near-IR region. Here, we describe technical details of a femtosecond time-resolved near-IR multiplex stimulated Raman spectrometer that we have recently developed. A description of signal generation and optimization, measurement, data acquisition, and calibration and correction of recorded data is provided as well. We present an application of our spectrometer to analyze the excited-state dynamics of &#946;-carotene in toluene solution. A C=C stretch band of &#946;-carotene in the second lowest excited singlet (S2) state and the lowest excited singlet (S1) state is clearly observed in the recorded time-resolved stimulated Raman spectra. The femtosecond time-resolved near-IR stimulated Raman spectrometer is applicable to the structural dynamics of &#960;-conjugate systems from simple molecules to complex materials.

Femtosecond time-resolved near-IR stimulated Raman spectroscopy was applied to &#946;-carotene in toluene solution. The concentration of the sample was 1 x 10-4 mol dm-3. The sample was photoexcited by the actinic pump pulse at 480 nm with a pulse energy of 1 &#956;J. Time-resolved stimulated Raman spectra of &#946;-carotene in toluene are shown in Figure 2A. The raw spectra contained strong Raman bands of the solvent toluene and a weak Raman band of &#...

Watch this Scientific Journal Video about Ultrafast Time-resolved Near-IR Stimulated Raman Measurements of Functional Ãâ‚¬-conjugate Systems at JoVE.com

Ultrafast Time-resolved Near-IR Stimulated Raman Measurements of Functional &#960;-conjugate Systems

Details of signal generation and optimization, measurement, data acquisition, and data handling for a femtosecond time-resolved near-IR stimulated Raman spectrometer are described. A near infrared stimulated Raman study on the excited-state dynamics of &#946;-carotene in toluene is shown as a representative application.

Femtosecond time-resolved stimulated Raman spectroscopy is a promising method of observing the structural dynamics of short-lived transients with near ...

ultrafast-time-resolved-near-ir-stimulated-raman-measurements

Research

JoVE Journal

Chemistry

7.1K Views.  Gakushuin University. Details of signal generation and optimization, measurement, data acquisition, and data handling for a femtosecond time-resolved near-IR stimulated Raman spectrometer are described. A near infrared stimulated Raman study on the excited-state dynamics of β-carotene in toluene is shown as a representative application.

Video: Ultrafast Time-resolved Near-IR Stimulated Raman Measurements of Functional π-conjugate Systems

High-pressure Sapphire Cell for Phase Equilibria Measurements of CO2/Organic/Water Systems

The high pressure sapphire cell apparatus was constructed to visually determine the composition of multiphase systems without physical sampling. Specifically, the sapphire cell enables visual data collection from multiple loadings to solve a set of material balances to precisely determine phase composition. Ternary phase diagrams can then be established to determine the proportion of each component in each phase at a given condition. In principle, any ternary system can be studied although ternary systems (gas-liquid-liquid) are the specific examples discussed herein. For instance, the ternary THF-Water-CO2 system was studied at 25 and 40&#160;&#176;C and is described herein. Of key importance, this technique does not require sampling. Circumventing the possible disturbance of the system equilibrium upon sampling, inherent measurement errors, and technical difficulties of physically sampling under pressure is a significant benefit of this technique. Perhaps as important, the sapphire cell also enables the direct visual observation of the phase behavior. In fact, as the CO2 pressure is increased, the homogeneous THF-Water solution phase splits at about 2 MPa. With this technique, it was possible to easily and clearly observe the cloud point and determine the composition of the newly formed phases as a function of pressure.
The data acquired with the sapphire cell technique can be used for many applications. In our case, we measured swelling and composition for tunable solvents, like gas-expanded liquids, gas-expanded ionic liquids and Organic Aqueous Tunable Systems (OATS)1-4. For the latest system, OATS, the high-pressure sapphire cell enabled the study of (1) phase behavior as a function of pressure and temperature, (2) composition of each phase (gas-liquid-liquid) as a function of pressure and temperature and (3) catalyst partitioning in the two liquid phases as a function of pressure and composition. Finally, the sapphire cell is an especially effective tool to gather accurate and reproducible measurements in a timely fashion.

High-pressure Sapphire Cell for Phase Equilibria Measurements of CO2/Organic/Water Systems

The high pressure sapphire cell apparatus is a unique tool to study, without sampling, phase behavior under a wide range of pressures. Using a cathetometer, very precise volume measurements can be recorded to measure liquid expansion and phase composition. Thus, this synthetic method enables the study of (1) phase equilibria of multi-component mixtures and (2) the partition behavior of catalyst or model compounds as a function of pressure.

The high pressure sapphire cell apparatus was constructed to visually determine the composition of multiphase systems without physical sampling. ...

Dissolution Dynamic Nuclear Polarization Instrumentation for Real-time Enzymatic Reaction Rate Measurements by NMR

The main limitation of NMR-based investigations is low sensitivity. This prompts for long acquisition times, thus preventing real-time NMR measurements of metabolic transformations. Hyperpolarization via dissolution DNP circumvents part of the sensitivity issues thanks to the large out-of-equilibrium nuclear magnetization stemming from the electron-to-nucleus spin polarization transfer. The high NMR signal obtained can be used to monitor chemical reactions in real time. The downside of hyperpolarized NMR resides in the limited time window available for signal acquisition, which is usually on the order of the nuclear spin longitudinal relaxation time constant, T1, or, in favorable cases, on the order of the relaxation time constant associated with the singlet-state of coupled nuclei, TLLS. Cellular uptake of endogenous molecules and metabolic rates can provide essential information on tumor development and drug response. Numerous previous hyperpolarized NMR studies have demonstrated the relevancy of pyruvate as a metabolic substrate for monitoring enzymatic activity in vivo. This work provides a detailed description of the experimental setup and methods required for the study of enzymatic reactions, in particular the pyruvate-to-lactate conversion rate in presence of lactate dehydrogenase (LDH), by hyperpolarized NMR.

The sensitivity enhancement provided by dissolution dynamic nuclear polarization (DNP) enables following metabolic processes in real time by NMR and MRI. The characteristics and performances of a dedicated dissolution DNP setup designed for study enzymatic reactions are discussed.

The main limitation of NMR-based investigations is low sensitivity. This prompts for long acquisition times, thus preventing real-time NMR measurements of ...

Preparation of Biopolymer Aerogels Using Green Solvents

Although the first reports on aerogels made by Kistler1 in the 1930s dealt with aerogels from both inorganic oxides (silica and others) and biopolymers (gelatin, agar, cellulose), only recently have biomasses been recognized as an abundant source of chemically diverse macromolecules for functional aerogel materials. Biopolymer aerogels (pectin, alginate, chitosan, cellulose, etc.) exhibit both specific inheritable functions of starting biopolymers and distinctive features of aerogels (80-99% porosity and specific surface up to 800 m2/g). This synergy of properties makes biopolymer aerogels promising candidates for a wide gamut of applications such as thermal insulation, tissue engineering and regenerative medicine, drug delivery systems, functional foods, catalysts, adsorbents and sensors. This work demonstrates the use of pressurized carbon dioxide (5 MPa) for the ionic cross linking of amidated pectin into hydrogels. Initially a biopolymer/salt dispersion is prepared in water. Under pressurized CO2 conditions, the pH of the biopolymer solution is lowered to 3 which releases the crosslinking cations from the salt to bind with the biopolymer yielding hydrogels. Solvent exchange to ethanol and further supercritical CO2 drying (10 - 12 MPa) yield aerogels. Obtained aerogels are ultra-porous with low density (as low as 0.02 g/cm3), high specific surface area (350 - 500 m2/g) and pore volume (3 - 7 cm3/g for pore sizes less than 150 nm).

A new way for the production of biopolymer-based aerogels by carbon dioxide (CO2) induced gelation is shown. The technique utilizes pressurized carbon dioxide (5 MPa) for the production of biopolymer hydrogels and supercritical CO2 (12 MPa) to convert gels into aerogels. The only solvents needed besides CO2 are water and ethanol.

Although the first reports on aerogels made by Kistler1 in the 1930s dealt with aerogels from both inorganic oxides (silica and others) and biopolymers ...

A Novel Technique for Raman Analysis of Highly Radioactive Samples Using Any Standard Micro-Raman Spectrometer

A novel approach for the Raman measurement of nuclear materials is reported in this paper. It consists of the enclosure of the radioactive sample in a tight capsule that isolates the material from the atmosphere. The capsule can optionally be filled with a chosen gas pressurized up to 20 bars. The micro-Raman measurement is performed through an optical-grade quartz window. This technique permits accurate Raman measurements with no need for the spectrometer to be enclosed in an alpha-tight containment. It therefore allows the use of all options of the Raman spectrometer, like multi-wavelength laser excitation, different polarizations, and single or triple spectrometer modes. Some examples of measurements are shown and discussed. First, some spectral features of a highly radioactive americium oxide sample (AmO2) are presented. Then, we report the Raman spectra of neptunium oxide (NpO2) samples, the interpretation of which is greatly improved by employing three different excitation wavelengths, 17O doping, and a triple mode configuration to measure the anti-stokes Raman lines. This last feature also allows the estimation of the sample surface temperature. Finally, data that were measured on a sample from Chernobyl lava, where phases are identified by Raman mapping, are shown.

We present a technique for Raman spectroscopic analysis of highly radioactive samples compatible with any standard micro-Raman spectrometer, without any radioactive contamination of the instrument. We also show some applications using actinide compounds and irradiated fuel materials.

A novel approach for the Raman measurement of nuclear materials is reported in this paper. It consists of the enclosure of the radioactive sample in a ...

Direct Imaging of Laser-driven Ultrafast Molecular Rotation

We present a method for visualizing laser-induced, ultrafast molecular rotational wave packet dynamics. We have developed a new 2-dimensional Coulomb explosion imaging setup in which a hitherto-impractical camera angle is realized. In our imaging technique, diatomic molecules are irradiated with a circularly polarized strong laser pulse. The ejected atomic ions are accelerated perpendicularly to the laser propagation. The ions lying in the laser polarization plane are selected through the use of a mechanical slit and imaged with a high-throughput, 2-dimensional detector installed parallel to the polarization plane. Because a circularly polarized (isotropic) Coulomb exploding pulse is used, the observed angular distribution of the ejected ions directly corresponds to the squared rotational wave function at the time of the pulse irradiation. To create a real-time movie of molecular rotation, the present imaging technique is combined with a femtosecond pump-probe optical setup in which the pump pulses create unidirectionally rotating molecular ensembles. Due to the high image throughput of our detection system, the pump-probe experimental condition can be easily optimized by monitoring a real-time snapshot. As a result, the quality of the observed movie is sufficiently high for visualizing the detailed wave nature of motion. We also note that the present technique can be implemented in existing standard ion imaging setups, offering a new camera angle or viewpoint for the molecular systems without the need for extensive modification.

We present a protocol for creating a real-time movie of a molecular rotational wave packet using a high-resolution Coulomb explosion imaging setup.

We present a method for visualizing laser-induced, ultrafast molecular rotational wave packet dynamics. We have developed a new 2-dimensional Coulomb ...

Time-resolved Photophysical Characterization of Triplet-harvesting Organic Compounds at an Oxygen-free Environment Using an iCCD Camera

Here, we present a sensible method of the acquisition and analysis of time-resolved photoluminescence using an ultrafast iCCD camera. This system enables the acquisition of photoluminescence spectra covering the time regime from nanoseconds up to 0.1 s. This enables us to follow the changes in the intensity (decay) and emission of the spectra over time. Using this method, it is possible to study diverse photophysical phenomena, such as the emission of phosphorescence, and the contributions of prompt and delayed fluorescence in molecules showing thermally activated delayed fluorescence (TADF). Remarkably, all spectra and decays are obtained in a single experiment. This can be done for solids (thin film, powder, crystal) and liquid samples, where the only limitations are the spectral sensitivity of the camera and the excitation wavelength (532 nm, 355 nm, 337 nm, and 266 nm). This technique is, thus, very important when investigating the excited state dynamics in organic emitters for their application in organic light-emitting diodes and other areas where triplet harvesting is of paramount importance. Since triplet states are strongly quenched by oxygen, emitters with efficient TADF luminescence, or those showing room temperature phosphorescence (RTP), must be correctly prepared in order to remove any dissolved oxygen from solutions and films. Otherwise, no long-lived emission will be observed. The method of degassing solid samples as presented in this work is basic and simple, but the degassing of liquid samples creates additional difficulties and is particularly interesting. A method of minimizing solvent loss and changing the sample concentration, while still enabling to remove oxygen in a very efficient and a repeatable manner, is presented in this work.

Here, we present a method of the spectroscopic characterization of organic molecules by means of time-resolved photoluminescence spectroscopy on the nanosecond-to-millisecond timescale in oxygen-free conditions. Methods to efficiently remove oxygen from the samples and, thus, limit luminescence quenching are also described.

Here, we present a sensible method of the acquisition and analysis of time-resolved photoluminescence using an ultrafast iCCD camera. This system enables ...

Measurement of Ultrafast Vibrational Coherences in Polyatomic Radical Cations with Strong-Field Adiabatic Ionization

We present a pump-probe method for preparing vibrational coherences in polyatomic radical cations and probing their ultrafast dynamics. By shifting the wavelength of the strong-field ionizing pump pulse from the commonly used 800 nm into the near-infrared (1200-1600 nm), the contribution of adiabatic electron tunneling to the ionization process increases relative to multiphoton absorption. Adiabatic ionization results in predominant population of the ground electronic state of the ion upon electron removal, which effectively prepares a coherent vibrational state (&#34;wave packet&#34;) amenable to subsequent excitation. In our experiments, the coherent vibrational dynamics are probed with a weak-field 800 nm pulse and the time-dependent yields of dissociation products measured in a time-of-flight mass spectrometer. We present the measurements on the molecule dimethyl methylphosphonate (DMMP) to illustrate how using 1500 nm pulses for excitation enhances the amplitude of coherent oscillations in ion yields by a factor of 10 as compared to 800 nm pulses. This protocol may be implemented in existing pump-probe setups through the incorporation of an optical parametric amplifier (OPA) for wavelength conversion.

We present a protocol for probing ultrafast vibrational coherences in polyatomic radical cations that result in molecular dissociation.

We present a pump-probe method for preparing vibrational coherences in polyatomic radical cations and probing their ultrafast dynamics. By shifting the ...

Improving High Viscosity Extrusion of Microcrystals for Time-resolved Serial Femtosecond Crystallography at X-ray Lasers

High-viscosity micro-extrusion injectors have dramatically reduced sample consumption in serial femtosecond crystallographic experiments (SFX) at X-ray free electron lasers (XFELs). A series of experiments using the light-driven proton pump bacteriorhodopsin have further established these injectors as a preferred option to deliver crystals for time-resolved serial femtosecond crystallography (TR-SFX) to resolve structural changes of proteins after photoactivation. To obtain multiple structural snapshots of high quality, it is essential to collect large amounts of data and ensure clearance of crystals between every pump laser pulse. Here, we describe in detail how we optimized the extrusion of bacteriorhodopsin microcrystals for our recent TR-SFX experiments at the Linac Coherent Light Source (LCLS). The goal of the method is to optimize extrusion for a stable and continuous flow while maintaining a high density of crystals to increase the rate at which data can be collected in a TR-SFX experiment. We achieve this goal by preparing lipidic cubic phase with a homogenous distribution of crystals using a novel three-way syringe coupling device followed by adjusting the sample composition based on measurements of the extrusion stability taken with a high-speed camera setup. The methodology can be adapted to optimize the flow of other microcrystals. The setup will be available for users of the new Swiss Free Electron Laser facility.

The success of a time-resolved serial femtosecond crystallography experiment is dependent on efficient sample delivery. Here, we describe protocols to optimize the extrusion of bacteriorhodopsin microcrystals from a high viscosity micro-extrusion injector. The methodology relies on sample homogenization with a novel three-way coupler and visualization with a high-speed camera.

High-viscosity micro-extrusion injectors have dramatically reduced sample consumption in serial femtosecond crystallographic experiments (SFX) at X-ray ...

Ultrafast Lignin Extraction from Unusual Mediterranean Lignocellulosic Residues

Pretreatment is still the most expensive step in lignocellulosic biorefinery processes. It must be made cost-effective by minimizing chemical requirements as well as power and heat consumption and by using environment-friendly solvents. Deep eutectic solvents (DESs) are key, green, and low-cost solvents in sustainable biorefineries. They are transparent mixtures characterized by low freezing points resulting from at least one hydrogen bond donor and one hydrogen bond acceptor. Although DESs are promising solvents, it is necessary to combine them with an economic heating technology, such as microwave irradiation, for competitive profitability. Microwave irradiation is a promising strategy to shorten the heating time and boost fractionation because it can rapidly attain the appropriate temperature. The aim of this study was to develop a one-step, rapid method for biomass fractionation and lignin extraction using a low-cost and biodegradable solvent. 
In this study, a microwave-assisted DES pretreatment was conducted for 60 s at 800 W, using three kinds of DESs. The DES mixtures were facilely prepared from choline chloride (ChCl) and three hydrogen-bond donors (HBDs): a monocarboxylic acid (lactic acid), a dicarboxylic acid (oxalic acid), and urea. This pretreatment was used for biomass fractionation and lignin recovery from marine residues (Posidonia leaves and aegagropile), agri-food byproducts (almond shells and olive pomace), forest residues (pinecones), and perennial lignocellulosic grasses (Stipa tenacissima). Further analyses were conducted to determine the yield, purity, and molecular weight distribution of the recovered lignin. In addition, the effect of DESs on the chemical functional groups in the extracted lignin was determined by Fourier-transform infrared (FTIR) spectroscopy. The results indicate that the ChCl-oxalic acid mixture affords the highest lignin purity and the lowest yield. The present study demonstrates that the DES-microwave process is an ultrafast, efficient, and cost-competitive technology for lignocellulosic biomass fractionation.

Deep eutectic solvent-based, microwave-assisted pretreatment is a green, fast, and efficient process for lignocellulosic fractionation and high-purity lignin recovery.

Pretreatment is still the most expensive step in lignocellulosic biorefinery processes. It must be made cost-effective by minimizing chemical requirements ...

Quantitative Atomic-Site Analysis of Functional Dopants/Point Defects in Crystalline Materials by Electron-Channeling-Enhanced Microanalysis

A novel elemental and chemical analysis scheme based on electron-channeling phenomena in crystalline materials is introduced, where the incident high-energy electron beam is rocked with the submicrometric pivot point fixed on a specimen. This method enables us to quantitatively derive the site occupancies and site-dependent chemical information of impurities or intentionally doped functional elements in a specimen, using energy-dispersive X-ray spectroscopy and electron energy-loss spectroscopy attached to a scanning transmission electron microscope, which is of significant interest to current materials science, particularly related to nanotechnologies. This scheme is applicable to any combination of elements even when the conventional Rietveld analysis by X-ray or neutron diffraction occasionally fails to provide the desired results because of limited sample sizes and close scattering factors of neighboring elements in the periodic table. In this methodological article, we demonstrate the basic experimental procedure and analysis method of the present beam-rocking microanalysis.

We provide a general outline of quantitative microanalysis methods for estimating the site occupancies of impurities and their chemical states by taking advantage of electron-channeling phenomena under incident electron beam-rocking conditions, which reliably extract information from minority species, light elements, oxygen vacancies, and other point/line/planar defects.