UC Berkeley

Abstract

Anion Photoelectron Spectroscopy of Exotic Species

By

Terry A. Yen

Doctor of Philosophy in Chemistry

University of California, Berkeley

Professor Daniel M. Neumark, Chair

Anion photoelectron spectroscopy is performed on a variety of small, unstable species in both the gas and condensed phases. For the gas-phase studies, the properties of the astrophysically significant molecules C₃N^- and C₅N^- and the biologically meaningful deprotonated DNA nucleobases were investigated. Spectra of C₃N^- and C_{5N^- were obtained at 283 nm using slow electron velocity-map imaging and at 213 nm using field-free time-of-flight, respectively. Adiabatic electron affinities for both species, a term value for the first excited state of C5N, and vibrational frequencies for the degenerate cis and trans bending modes of C3N were determined. Spectra of deprotonated thymine and deprotonated cytosine at 213 nm were obtained to explore their excited state dynamics to understand the photostability of DNA.}

For the condensed phase studies, a new spectrometer, the liquid microjet apparatus, was assembled and used to measure the vertical binding energy of the solvated electron. A microjet flowing a salt solution intersects a laser at either 266 nm or 213 nm. Two photons from a single nanosecond laser pulse are used to first generate solvated electrons using charge-transfer-to-solvent excitation and to then eject them into vacuum, where they are detected using field-free time-of-flight.