Strong Field Ionization-Photofragmentation on Ultrafast Evolution of Electronic States of Toluene Cations.

Ultrafast time-resolved strong field ionization-photofragmentation (SFI-PF) has emerged as a useful method for investigation of dynamics of molecular cations. Here we perform a SFI-PF study on the electronic states of toluene cations. By measuring the ion yields as a function of delay time, we obtain the transients of both parent and daughter ions, which show ultrafast decays and out-of-phase oscillations. The results provide the first experimental evidence of D1-D0 ultrafast relaxation of toluene cations occurring in about 530 fs and indicate coincident resonance between the vibrational states in D1 and D0 leading to oscillations with a period of about 2.05 ps. Our study should shed some light on the ultrafast photochemistry involving complex molecular cations.