title: Caveats in the interpretation of time-resolved photoionization measurements: A photoelectron imaging study of pyrrole.
abstract: We report time-resolved photoelectron imaging studies of gas-phase pyrrole over the 267-240 nm excitation region, recorded in conjunction with a 300 nm probe. Of specific interest is the lowest-lying (3s/πσ*) state, which exhibits very weak oscillator strength but is thought to be excited directly at wavelengths ≤254 nm. We conclude, however, that the only significant contribution to our photoelectron data at all wavelengths investigated is from non-resonant ionization. Our findings do not rule out (3s/πσ*) state excitation (as appears to be confirmed by supporting time-resolved ion-yield measurements) but do potentially highlight important caveats regarding the use and interpretation of photoreactant ionization measurements to interrogate dynamical processes in systems exhibiting significant topological differences between the potential energy surfaces of the neutral and cation states.
authors.affiliation: Institute of Photonics and Quantum Sciences, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom.
authors.forename: Stuart W
authors.initials: SW
authors.lastname: Crane
authors.affiliation: Institute of Photonics and Quantum Sciences, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom.
authors.forename: Magdalena M
authors.initials: MM
authors.lastname: Zawadzki
authors.affiliation: Institute of Photonics and Quantum Sciences, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom.
authors.forename: James O F
authors.initials: JO
authors.lastname: Thompson
authors.affiliation: Institute of Photonics and Quantum Sciences, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom.
authors.forename: Nikoleta
authors.initials: N
authors.lastname: Kotsina
authors.affiliation: Institute of Photonics and Quantum Sciences, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom.
authors.forename: Omair
authors.initials: O
authors.lastname: Ghafur
authors.affiliation: Institute of Photonics and Quantum Sciences, Heriot-Watt University, Edinburgh EH14 4AS, United Kingdom.
authors.forename: Dave
authors.initials: D
authors.lastname: Townsend