Very accurate gas-phase thermochemistry through photoelectron photoion coincidence (PEPICO) spectroscopy
type: CreativeWork
description: Five projects are presented here that use Photoelectron Photoion Coincidence (PEPICO) Spectroscopy to determine high-accuracy thermochemical data on small and intermediate size molecules and radicals that are relevant in modeling combustion and atmospheric processes. Some of the experiments were carried out on the laboratory-based Threshold PEPICO (TPEPICO) apparatus which has the advantage of having a low-temperature inlet system and unlimited measurement time, while most of the projects involved the use of the Imaging PEPICO (iPEPICO) apparatus at the Swiss Light Source, which is capable to determine ionic dissociation energies to sub-kJ/mol accuracy. The iPEPICO on the synchrotron beamline was also useful where measurements required energies in excess of 14 eV. The modeling framework of PEPICO is based on the RRKM statistical theory of dissociation kinetics and statistical energy distributions and models complex dissociation pathways to extract both kinetics and thermochemical data from the experiment. In the first project, we measured the onsets of Br- and I-loss reactions for C 2 H 5 Br and C 2 H 5 I using TPEPICO, respectively. The heats of formations of the two molecules are related through the ethyl cation, which was used in their determination. The second project involved measuring Cl-loss from four S i O j Cl k compounds viz. SCl 2 , S 2 Cl 2 , SOCl 2 , and SO 2 Cl 2 to obtain reliable thermochemistry. The second Cl-loss from S 2 Cl 2 + and SOCl 2 + helped us conclude that assuming three-dimensional translational degrees of freedom yields a more reliable statistical model of product-energy distributions. The third project investigated methanol and its isotopologues to explore the dissociation pathways through the H/D-losses. The 0 K appearance energies were used to determine the accurate heat of formation of CH 2 OH and the proton affinity of formaldehyde. The fourth project explores the dissociation pathways of cis -1-bromopropene, trans -1-bromopropene, …
abstract: Five projects are presented here that use Photoelectron Photoion Coincidence (PEPICO) Spectroscopy to determine high-accuracy thermochemical data on small and intermediate size molecules and radicals that are relevant in modeling combustion and atmospheric processes. Some of the experiments were carried out on the laboratory-based Threshold PEPICO (TPEPICO) apparatus which has the advantage of having a low-temperature inlet system and unlimited measurement time, while most of the projects involved the use of the Imaging PEPICO (iPEPICO) apparatus at the Swiss Light Source, which is capable to determine ionic dissociation energies to sub-kJ/mol accuracy. The iPEPICO on the synchrotron beamline was also useful where measurements required energies in excess of 14 eV. The modeling framework of PEPICO is based on the RRKM statistical theory of dissociation kinetics and statistical energy distributions and models complex dissociation pathways to extract both kinetics and thermochemical data from the experiment. In the first project, we measured the onsets of Br- and I-loss reactions for C 2 H 5 Br and C 2 H 5 I using TPEPICO, respectively. The heats of formations of the two molecules are related through the ethyl cation, which was used in their determination. The second project involved measuring Cl-loss from four S i O j Cl k compounds viz. SCl 2 , S 2 Cl 2 , SOCl 2 , and SO 2 Cl 2 to obtain reliable thermochemistry. The second Cl-loss from S 2 Cl 2 + and SOCl 2 + helped us conclude that assuming three-dimensional translational degrees of freedom yields a more reliable statistical model of product-energy distributions. The third project investigated methanol and its isotopologues to explore the dissociation pathways through the H/D-losses. The 0 K appearance energies were used to determine the accurate heat of formation of CH 2 OH and the proton affinity of formaldehyde. The fourth project explores the dissociation pathways of cis -1-bromopropene, trans -1-bromopropene, …
author: Borkar, Sampada N.
keywords: Analytical chemistry, Physical chemistry, Pure sciences, Kinetics, Mass spectrometry, Photoelectron photoion coincidence, Thermochemistry, Chemicals and Drugs, Chemistry, Medical Pharmacology, Medicinal-Pharmaceutical Chemistry, Medicine and Health Sciences, Pharmaceutical Preparations, Pharmacy and Pharmaceutical Sciences, Physical Sciences and Mathematics
license: http://rightsstatements.org/vocab/InC/1.0/
date published: 2013-01-01T08:00:00Z
date modified: 2026-07-24T05:36:00Z
provider: University of the Pacific
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of the Pacific