14.2 : 原子分光法: 温度の影響

Recall that atomization or the breakdown of liquid samples into gas-phase atoms—is crucial in atomic spectroscopy.

The atomization efficiency increases with temperature. In addition, temperature affects the proportion of atoms in excited or ionized states, impacting the signal strength.

The magnitude of the temperature effect is estimated from the Maxwell–Boltzmann expression, describing the relative populations of the ground and excited states at thermal equilibrium.

At 2500 K,  nearly 0.017% of sodium atoms are excited. With a 100 K rise in temperature, the relative excited-state population increases by 45% but decreases the ground-state population negligibly.

Since the excited-state relaxation process causes emission of light, temperature control is critical in AES for consistent emission intensity.

In contrast, AAS and AFS intensities depend on the ground-state populations.

However, temperature changes affect the total population overall, and high temperature causes ionization interference, both of which affect the spectral intensity.

Additionally, all atomic spectroscopy at high temperature shows a more pronounced Doppler effect, with spectral line broadening and peak height reduction.