Photo-induced intramolecular electron transfer and intramolecular vibrational relaxation of rhodamine 6G in DMSO revealed by multiplex transient grating spectroscopy

Photo-induced intramolecular electron transfer (PIET) and intramolecular vibrational relaxation (IVR) dynamics of the excited state of rhodamine 6G (Rh6G⁺) in DMSO are investigated by multiplex transient grating. Two major components are resolved in the dynamics of Rh6G⁺. The first component, with a lifetime τ_PIET = 140 fs-260 fs, is attributed to PIET from the phenyl ring to the xanthene plane. The IVR process occurring in the range τ_IVR = 3.3 ps-5.2 ps is much slower than the first component. The PIET and IVR processes occurring in the excited state of Rh6G⁺ are quantitatively determined, and a better understanding of the relationship between these processes is obtained.