Abstract

Recent progress in the generation of intense, tunable picosecond pulses has opened the field of time-resolved nonlinear transmission studies of vibrational absorption bands in the electronic ground state of liquids. In spite of the short molecular time constants involved and the necessary high intensity level of ∼ 10¹¹ W/cm², large population changes of several ten per cent can be achieved.¹⁾ Experimentally we work with resonantly tuned pulses (2700-4000 cm⁻¹) of 15 ps duration which are generated by a mode locked YAG laser system and a multiple-step parametric generator-amplifier device. Measuring the transmission change of delayed weak probing pulses of same frequency as the excitation pulse, the time evolution of the population difference between upper vibrational level and the vibrational ground state is observed.

© 1986 Optical Society of America