Homonuclear 2D experiments measure differences in magnetic environment for a single TYPE of nuclei.

The standard proton COSY-90 employs a second 90-degree pulse to reveal through-bond structural relationships between protons separated by two to three bonds.

In contrast, COSY-45 applies a 45-degree pulse, sacrificing intensity for better detail and resolution.

Long-range or LR-COSY experiments extend the evolution and detection periods to identify correlations not visible in standard COSY.

Relayed COSY adds extra pulses to the standard pulse sequence to produce cross peaks between cross peaks, showing specific molecular connections hidden by overlapping signals.

However, the total correlation spectroscopy experiment reveals all through-bond proton correlations within a spin system, providing data as though from simultaneous COSY, LR-COSY, and relayed COSY experiments.

Meanwhile, correlations between spatially close yet non-coupled protons are revealed through Nuclear Overhauser Effect Spectroscopy.