Femtosecond two-dimensional infrared spectroscopy

The dynamics occurring amongst the structures of peptides and small proteins present significant questions that are not readily addressed by conventional methods. Multiple pulse infrared experiments provide a promising alternative. The time resolution is easily fast enough to intercept the structures on different parts of the free energy surfaces. This paper reviews how infrared spectroscopy can be optimized by stretching it into two dimensions thereby making it possible to separately examine and assign the cross peaks arising from the interaction of different amide oscillators in the molecule. A variety of approaches such as pump/probe, self-heterodyned pump/probe, three pulse photon echo and spectrally resolved echoes are described which are analogous to magnetic resonance schemes.