Abstract

I₂ doped condensed rare gases are studied as prototypes of many-body interactions which govern chemistry and photodynamics in condensed media. The information content of frequency domain spectroscopies with respect to dynamics in such systems is highly limited. This is understood by dissecting the time correlation functions of coupled many-degrees of freedom through simulations that include phase information via classical action integrals of individual coordinates.¹ While phase coherences in such systems are limited to a single vibrational period, population coherences outlast energy dissipation. As such, spectroscopies that probe population coherences can be used to follow the time evolution of many-body dynamics for many periods, for as long as the dynamics remains localized in classical phase space. It can be rigorously shown that femtosecond pump-probe spectroscopy is such a tool, and realizations of the principle through several examples will be illustrated. A new dimension in such measurements is afforded through the control of the chirp in both pump and probe pulses.² Measurements with chirped probe pulses provide vectorial information about the evolving dynamics, and allow interrogation of local gradients of difference potentials. Chirped pump pulses interrogate system memory, and characterize dissipation.

© 1996 Optical Society of America