Nonlinear Optical Techniques for Probing Dephasing of Molecules and Excitons: Nano and Picosecond Dynamics

A brief account of some of our recent work at CalTech on the time resolved spectra of gases and solids in the nano and sub-picosecond time regimes was given. First, we discussed the concepts involved in nonlinear optical techniques and their relationships to optical T1 and T2 measured in large (pentacene) and small (iodine) molecules. Second, a description for nanosecond techniques was given. Third, we presented a picosecond reflection technique for probing exciton dynamics and surface states in mole cular crystals. Finally, we mentioned a curious effect which is in analogy with the optical Ramsey fringes. This effect is observed in molecules excited to one-photon states in contrast to previous observations made in two-photon transitions. Since there was necessarily some overlap with the material presented at the conference on Advances in Laser Chemistry organized by one of the authors (A.H.Z.), the reader is referred to [1]