Applications of a Mid Infrared Free Electron Laser in Picosecond and Nonlinear Optical Spectroscopies

It has been suggested that the 1650 cm sup -1 band in low-temperature infrared spectrum of acetanilide is the absorption of nonlinear excitations similar to silitons in alpha-helices as proposed by Davydov. We report the picosecond transient bleaching experiments on polycrystalline acetanilide using the infrared free electron laser. The T sub 1 lifetime is determined to be 15+-10 picoseconds. The results will be discussed in the context of structural changes as the origin of the intensity increases of 1650 cm sup -1 absorption band at low temperature.