Photoinitiated Dynamics of Cluster Anions via Photoelectron Imaging and Photofragment Mass Spectrometry
type: CreativeWork
description: Mass-selected cluster anions are employed as model micro-solutions to study solvent effects on the structural motifs and electronic structure of anionic solutes, including the roles of the solvent in controlling the outcomes of photochemical processes. Interaction of light with cluster anions can potentially lead to cluster photodissociation in addition to photodetachment. We investigate these competing processes by means of photoelectron imaging spectroscopy combined with tandem time-of-flight (TOF) mass spectrometry. Photoelectron images are reported for members of the [(CO2)n(H2O)m]- cluster series. For homogeneous solvation, the photodetachment bands show evidence of cluster core switching between a CO2- monomer anion and a covalent (CO2)2- dimer anionic core, confirming previous observations. The Photoelectron Angular Distributions (PADs) of the monomer- and dimer-based clusters reveal an interference effect that result in similar PADs. Stabilization of the metastable CO2- anion by water solvent molecules is highlighted because its ability to "trap" the excess electron on CO2. Most surprising is the effect of the water solvent in quenching the autodetachment channel in excited states normally embedded in the electron detachment continuum, allowing excited CO2-(H2O)m clusters to follow reaction paths that lead to cluster fragmentation. Observed O- based photoproducts are attributed to photodissociation of the CO2- cluster core and are dominant for small parent clusters, whereas a water evaporation channel dominates for larger clusters. Addition of a second CO2 to these clusters is shown to preferentially form monomer based clusters, whose photodissociation exhibit an additional CO3- based channel, characteristic of a photoinitiated intracluster ion-molecule reaction between nascent O- and the additional CO2 solvent molecule. Changes in the PADs of NO- are monitored as a function of electron kinetic energy for the NO-(N2O)n and NO-(H2O)n cluster anions. In contra…
abstract: Mass-selected cluster anions are employed as model micro-solutions to study solvent effects on the structural motifs and electronic structure of anionic solutes, including the roles of the solvent in controlling the outcomes of photochemical processes. Interaction of light with cluster anions can potentially lead to cluster photodissociation in addition to photodetachment. We investigate these competing processes by means of photoelectron imaging spectroscopy combined with tandem time-of-flight (TOF) mass spectrometry. Photoelectron images are reported for members of the [(CO2)n(H2O)m]- cluster series. For homogeneous solvation, the photodetachment bands show evidence of cluster core switching between a CO2- monomer anion and a covalent (CO2)2- dimer anionic core, confirming previous observations. The Photoelectron Angular Distributions (PADs) of the monomer- and dimer-based clusters reveal an interference effect that result in similar PADs. Stabilization of the metastable CO2- anion by water solvent molecules is highlighted because its ability to "trap" the excess electron on CO2. Most surprising is the effect of the water solvent in quenching the autodetachment channel in excited states normally embedded in the electron detachment continuum, allowing excited CO2-(H2O)m clusters to follow reaction paths that lead to cluster fragmentation. Observed O- based photoproducts are attributed to photodissociation of the CO2- cluster core and are dominant for small parent clusters, whereas a water evaporation channel dominates for larger clusters. Addition of a second CO2 to these clusters is shown to preferentially form monomer based clusters, whose photodissociation exhibit an additional CO3- based channel, characteristic of a photoinitiated intracluster ion-molecule reaction between nascent O- and the additional CO2 solvent molecule. Changes in the PADs of NO- are monitored as a function of electron kinetic energy for the NO-(N2O)n and NO-(H2O)n cluster anions. In contra…
author: Velarde, Luis Antonio
language: en
keywords: Photoelectron Imaging, Cluster Anions, Photodissociation, Electron Scattering
date published: 2008
date modified: 2026-07-24T00:56:22Z
provider: University of Arizona
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: The University of Arizona.

PropertyValue
property ID: Handle
value: http://hdl.handle.net/10150/195042