The nuclear spin dependence of the reaction of H3+ with H2 and the proposed spectroscopic investigation of HO2+

High-resolution spectroscopy of molecular ions has been proven to be a difficult endeavor. Generating significant quantities of the desired ions and discriminating ions from neutrals are among some of the many difficulties surrounding the spectroscopic studies of these species. Despite these difficulties, molecular ions and their reactions play important roles as intermediates in organic reactions, reactants in combustion chemistry, species in biological processes such as respiration, as interstellar species, and as species found in terrestrial and extraterrestrial atmospheres. Although extensive research has been devoted to study these species and their reactions, scientists have barely ``scratched the surface'' in the realm of molecular ions. One of the simplest molecular ions, H₃⁺, has been measured spectroscopically in the laboratory and observed by astronomers in the interstellar medium, the galactic center, and planetary atmospheres. Both H₃⁺ and its parent neutral, H₂, exist in two nuclear spin configurations, \emph{ortho} and \emph{para}, and yield unique spectral signatures that can be measured in the laboratory and in astronomical environments. Most importantly, these species have been found to be useful temperature probes of interstellar clouds. However, a temperature discrepancy arises when comparing the temperatures calculated from each species. Since the chemistry of H₂ has been well established, these findings indicate that the regulation of the nuclear spin states of H₃⁺ is not well understood. The nuclear spin configuration of interstellar H₃⁺ is postulated to be governed by the reaction of H₃⁺ $+$ H₂ $\rightarrow$ H₂ $+$~H₃⁺ and is one of the topics explored in this work. This reaction is investigated in the laboratory by spectroscopically monitoring the populations of several low-energy levels of \emph{ortho}- and \emph{para}-H₃⁺ in hydrogenic plasmas of varying \emph{para}-H₂ enrichments. Measurements were taken at room temperature and for the first time, at liquid nitrogen temperatures. Steady-state modeling is employed to infer the ratio of the rates of the hop and exchange pathways of the above reaction and aids in the understanding of how the distribution of the nuclear spin states of H₃⁺ is regulated in the interstellar medium. This study will aid in understanding of the temperature discrepancy found between H₂ and H₃⁺ in hopes to improve the viability of H₃⁺ as a temperature probe in astronomical environments where H₂ measurements are impossible or not readily available. Finally, a larger polyatomic molecular ion, HO₂⁺, will be discussed in the final chapter. Although many simple polyatomic ions have been studied, the species HO₂⁺ has eluded detection for nearly three decades. Given the current theoretical information and past experimental attempts, a proposed experiment for the detection of this species is outlined.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Chemistry

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2011

Author dc:creator

• Kauffman, Carrie A.

Contributors dc:contributor

• McCall, Benjamin J.

• H3+
• hydrogen
• spectroscopy
• plasma
• HO2+
• astrochemistry

Statement dc:rights

• Copyright 2011 Carrie A. Kauffman

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/24319

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/24319