For 10 points, name this spectroscopic technique that uses wavelengths longer than visible light.
Ultrafast variations of this technique can either use a double-resonance approach or the time domain vibrational echo method, which both use femtosecond lasers. The maximum resolution in this procedure is inversely proportional to the path length, and a rightward peak shift in this technique is indicative of pi backbonding. Liquid paraffin or nujol can be used as a mulling agent in this technique, whose sample is smeared between potassium bromide disks. Normal modes only appear for molecules with a dipole moment, and unique classification is obtained via complex fingerprint region. Some modes are obtained from scissoring, wagging, twisting, and rocking of molecules, and distinctive peaks occur due to symmetric and asymmetric stretching. For 10 points, name this spectroscopic technique that uses wavelengths longer than visible light.
Ultrafast variations of this technique can either use a double-resonance approach or the time domain vibrational echo method, which both use femtosecond lasers.
{Infrared spect}roscopy or {IR spec}troscopy (Accept {Fourier Transform IR spec} or {2D/Two-dimensional IR spec})