Vibrational dephasing measurements with cw mode-locked dye lasers

Abstract

Recent advances in the development of synchronously mode‐locked dye‐laser systems have permitted the first low‐power measurement of the time‐resolved dephasing dynamics of a Raman active molecular vibration. Excitation and delayed probing of the coherent ensemble of vibrators is accomplished with the help of synchronized picosecond pulse trains from two independently tunable mode‐locked dye lasers. A new probe technique, based on a gain measurement, is employed that provides a signal that scales linearly with the coherent vibrational amplitude. We demonstrate this technique with the first measurement of the dephasing dynamics of the normal mode (656.5 cm⁻¹) of CS₂ in the liquid state. An exponential decay with time constant 20±1 psec is obtained for the isotropic component of the coherent scattering.