Abstract

Preparing and studying molecules on a femtosecond time scale in well defined vibrational states in the electronic ground state, is an important starting point for many experiments. The standard approach is to populate these states by Stimulated Emission Pumping (SEP) and probe them by schemes such as time delayed four wave mixing (TDFWM). Two pulses (pump and Stokes frequencies) simultaneously prepare the molecule, and a third pulse probes the coherently prepared molecule at a variable delay. Fig. 1(a) depicts a typical observation for Iodine: at negative probe delay the excited state vibrations are seen, and at positive delays, ground state vibrations are evident. However, due to the reduced Frank Condon overlap with higher vibrational states, it is only possible to prepare relatively low lying ground state vibrations, and while probing the prepared molecule, the contributions from the ground and excited states are mixed together.

© 1999 Optical Society of America