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Ultrafast Nonlinear Spectroscopic Techniques in the Gas Phase and Their Density Matrix Representation

2002; American Chemical Society; Volume: 106; Issue: 5 Linguagem: Inglês

10.1021/jp010451l

1520-5215

Bruna Irene Grimberg, Vadim V. Lozovoy, Marcos Dantus, Shaul Mukamel,

Laser-Matter Interactions and Applications

We survey the possible time-resolved three pulse nonlinear spectroscopic techniques and their application to gas-phase samples. The role of each of the interacting electric fields is specified, and the nature of the signal is interpreted using the density matrix representation. Simulations of these nonlinear optical signals are based on the perturbative solution of the Liouville equation for the density matrix to third order in the applied fields. We present closed expressions for the integrated and frequency dispersed signals that identify the type of molecular response for each technique and give the signal dependence on the various time delays between laser pulses. We choose a simple experimental system, two-electronic states coupled to a single vibrational mode of diatomic iodine, with weak dephasing, to illustrate various molecular polarization responses in four-wave mixing experiments including pump−probe, reverse transient grating, and photon echo. These signals and their simulations illustrate how the time delays between pulses can be effectively used to control the optical response of the molecular system.