The application of femtosecond time-resolved coherent anti-Stokes Raman scattering for the investigation of ground and excited state molecular dynamics of molecules in the gas phase

In this study, we have employed femtosecond time-resolved CARS (coherent anti-Stokes Raman scattering) spectroscopy in order to gain information about the molecular dynamics evolving on the electronic excited as well as ground state potential energy surfaces (PES) of iodine and bromine in the gas phase. The coherences of the wave packet in the temporal transients of the molecules excited by the ultrashort laser pulses are analyzed by means of fast Fourier transform calculations as well as by a simple model describing the purely rotational contribution. The latter is able to describe the rotational coherence seen for the excited but not for the ground-state dynamics. Information about vibrational dynamics is extracted from the transients reflecting the wave packet motion on both the ground and excited-state PES.