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 (cohere nt anti-Stokes Raman scattering) spectroscopy in order to gain informa tion about the molecular dynamics evolving on the electronic excited a s well as ground state potential energy surfaces (PES) of iodine and b romine in the gas phase. The coherences of the wave packet in the temp oral transients of the molecules excited by the ultrashort laser pulse s are analyzed by means of fast Fourier transform calculations as well as by a simple model describing the purely rotational contribution. T he latter is able to describe the rotational coherence seen for the ex cited but not for the ground-state dynamics. Information about vibrati onal dynamics is extracted from the transients reflecting the wave pac ket motion on both the ground and excited-state PES.