Excited state dynamics in tetra tolyl porphyrins studied using degenerate four wave mixing with incoherent light and ps pulses

Abstract

We present our experimental results on the excited state dynamics in several tetra tolyl porphyrins (with different central metal-ions) studied using degenerate four wave mixing with nanosecond incoherent light (DFWM-IL) and picosecond time-resolved four wave mixing (DFWM-PS). Incoherent light studies indicate three lifetimes, which have been attributed to different excited states. The shortest component with a decay constant of < 170 fs is due to the vibrational relaxation in the higher excited singlet states S_n(T₂), 3-6 ps component is due to the vibrational relaxation of the Franck-Condon states in S₁(t_vib), and the long component of 20-100 ps is due to the population relaxation (T₁) from S₁ to S₀. The population relaxation times obtained from time-resolved DFWM studies using a picosecond laser substantiates these results.