title: Time-resolved photoionization spectroscopy of mixed Rydberg-valence states: indole case study.
abstract: Time-resolved photoelectron imaging was used to study non-adiabatic relaxation dynamics in gas-phase indole following photo-excitation at 267 nm and 258 nm. Our data analysis was supported by various ab initio calculations using both coupled cluster and density functional methods. The highly differential energy- and angle-resolved information provided by our experimental approach provides extremely subtle details of the complex interactions occurring between several low-lying electronically excited states. In particular, new insight into the role and fate of the mixed Rydberg-valence 3s/πσ* state is revealed. This includes population residing on the excited state surface at large N-H separations for a relatively long period of time (∼1 ps) prior to dissociation and/or internal conversion. Our findings may, in part, be rationalized by considering the rapid evolution of this state's electronic character as the N-H stretching coordinate is extended - as extensively demonstrated in the supporting theory. Overall, our findings highlight a number of important general caveats regarding the nature of mixed Rydberg-valence excited states, their spectral signatures and detection sensitivity in photoionization measurements, and the evaluation of their overall importance in mediating electronic relaxation in a wide range of small model-chromophore systems providing bio-molecular analogues - a topic of considerable interest within the chemical dynamics community over the last decade.
authors.affiliation: Institute of Photonics & Quantum Sciences, Heriot-Watt University, Edinburgh, EH14 4AS, UK. D.Townsend@hw.ac.uk.
authors.forename: Magdalena M
authors.initials: MM
authors.lastname: Zawadzki
authors.forename: James O F
authors.initials: JO
authors.lastname: Thompson
authors.forename: Emma A
authors.initials: EA
authors.lastname: Burgess
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Paterson
authors.forename: Dave
authors.initials: D
authors.lastname: Townsend