NUMERICAL STUDY OF INDUCED POLARIZATION DYNAMICS IN ULTRAFAST SPECTRAL HOLE-BURNING EXPERIMENTS

We develop a theoretical description of time and frequency resolved tr ansient spectroscopy in non-collinear geometry in a more complete way in respect to the interaction between the applied electric fields and the induced population changes in the sample. For this purpose we dedu ce a set of differential equations considering a vibrational mode exhi biting finite phase relaxation and an inhomogeneous broadening with cr oss-relaxation and rotation of the molecules with an average rotation time. In order to describe the electric fields according to experiment al conditions a different chirp of the two fields is included in the m odel as well as calculation of probing components parallel and perpend icular in respect to the excitation. The coherent interaction is solel y seen in the parallel probing signal. A time dependent evolution of t he transient spectral hole is inferred from the calculations, strongly influenced by phase relaxation. Experimental data on diluted methanol with excitation of the OH-stretching mode demonstrates a temporal evo lution of the transient hole in accordance to the calculations. (C) 19 98 Elsevier Science B.V. All rights reserved.