Time- and frequency-resolved photoionisation of the allyl radical

Abstract

We report picosecond time-resolved pump–probe photoelectron spectra of the allyl radical, C₃H₅, and the fully deuterated allyl, C₃D₅, carried out in order to elucidate the primary photophysical processes upon UV excitation. It is shown that the UV bands of allyl decay in a two-step process: the first step is an internal conversion to the lower-lying A-state within 20 ps or less, while the second step is a very fast decay from the A-state to the electronic ground state through a conical intersection. In addition we report the first zero kinetic energy (ZEKE) photoelectron spectrum of allyl, yielding an ionisation energy of 65762 cm⁻¹.