Microwave and Millimeter Wave Astrochemistry: Laboratory Studies of Transition Metal-Containing Free Radicals and Spectroscopic Observations of Molecular Interstellar Environments

Persistent Link:
http://hdl.handle.net/10150/306775
Title:
Microwave and Millimeter Wave Astrochemistry: Laboratory Studies of Transition Metal-Containing Free Radicals and Spectroscopic Observations of Molecular Interstellar Environments
Author:
Adande, Gilles Rapotchombo
Issue Date:
2013
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Progress in our understanding of the chemical composition of the interstellar medium leans both on laboratory analyses of high resolution rotational spectra from molecules that may be present in these regions, and on radio astronomical observations of molecular tracers to constrain astrochemical models. Due to the thermodynamic conditions in outer space, some molecules likely to be found in interstellar regions in relevant abundances are open shell radicals. In a series of laboratory studies, the pure rotational spectra of the transition metal containing radicals sulfur species ScS, YS, VS and ZnSH were obtained for the first time. In addition to accurate and precise rest frequencies for these species, bonding characteristics were determined from fine and hyperfine molecular parameters. It was found that these sulfides have a higher degree of covalent bonding than their mostly ionic oxide counterparts. Isomers and isotope ratios are excellent diagnostic tools for a variety of astrochemical models. From radio observations of isotopes of nitrile species, the galactic gradient of ¹⁴N/¹⁵N was accurately established. A further study of this ratio in carbon rich asymptotic giant branch stars provided observational evidence for an unknown process in J type carbon stars, and highlighted the need to update stellar nucleosynthesis models. Proper radiative transfer modeling of the emission spectra of interstellar molecules can yield a wealth of information about the abundance and distribution of these species within the observed sources. To model the asymmetric emission of SO and SO₂ in oxygen-rich supergiants, an in-house code was developed, and successfully applied to gain insight into circumstellar sulfur chemistry of VY Canis Majoris. It was concluded that current astrochemistry kinetic models, based on spherical symmetry assumptions, need to be revisited.
Type:
text; Electronic Dissertation
Keywords:
Radioastronomy; Rotational Spectroscopy; Small Radicals; Chemistry; Interstellar Medium
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Chemistry
Degree Grantor:
University of Arizona
Advisor:
Ziurys, Lucy M.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleMicrowave and Millimeter Wave Astrochemistry: Laboratory Studies of Transition Metal-Containing Free Radicals and Spectroscopic Observations of Molecular Interstellar Environmentsen_US
dc.creatorAdande, Gilles Rapotchomboen_US
dc.contributor.authorAdande, Gilles Rapotchomboen_US
dc.date.issued2013-
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractProgress in our understanding of the chemical composition of the interstellar medium leans both on laboratory analyses of high resolution rotational spectra from molecules that may be present in these regions, and on radio astronomical observations of molecular tracers to constrain astrochemical models. Due to the thermodynamic conditions in outer space, some molecules likely to be found in interstellar regions in relevant abundances are open shell radicals. In a series of laboratory studies, the pure rotational spectra of the transition metal containing radicals sulfur species ScS, YS, VS and ZnSH were obtained for the first time. In addition to accurate and precise rest frequencies for these species, bonding characteristics were determined from fine and hyperfine molecular parameters. It was found that these sulfides have a higher degree of covalent bonding than their mostly ionic oxide counterparts. Isomers and isotope ratios are excellent diagnostic tools for a variety of astrochemical models. From radio observations of isotopes of nitrile species, the galactic gradient of ¹⁴N/¹⁵N was accurately established. A further study of this ratio in carbon rich asymptotic giant branch stars provided observational evidence for an unknown process in J type carbon stars, and highlighted the need to update stellar nucleosynthesis models. Proper radiative transfer modeling of the emission spectra of interstellar molecules can yield a wealth of information about the abundance and distribution of these species within the observed sources. To model the asymmetric emission of SO and SO₂ in oxygen-rich supergiants, an in-house code was developed, and successfully applied to gain insight into circumstellar sulfur chemistry of VY Canis Majoris. It was concluded that current astrochemistry kinetic models, based on spherical symmetry assumptions, need to be revisited.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectRadioastronomyen_US
dc.subjectRotational Spectroscopyen_US
dc.subjectSmall Radicalsen_US
dc.subjectChemistryen_US
dc.subjectInterstellar Mediumen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineChemistryen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorZiurys, Lucy M.en_US
dc.contributor.committeememberZiurys, Lucy M.en_US
dc.contributor.committeememberBrown, Michael F.en_US
dc.contributor.committeememberSanov, Andreien_US
dc.contributor.committeememberWoolf, Neville J.en_US
dc.contributor.committeememberPolt, Robin L.en_US
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