Investigating the Molecular Complexity of the Interstellar Medium Open Access

Kroll, Jay Arthur (2012)

Permanent URL: https://etd.library.emory.edu/concern/etds/8623hz604?locale=en
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Abstract

Abstract
Investigating the Molecular Complexity of the Interstellar Medium


A new supersonic expansion source has been developed to produce unstable molecules of
astrochemical interest through O(1D) insertion reactions. This source has been designed to
allow for the production of O(1D) through photolysis of Ozone (O3) without photolyzing the
precursor organic molecules. In addition the rotational spectrum of methyl ethyl ketone (MEK)
has been acquired from 8GHz to 1THz. The spectrum has been analyzed using three spectral
fitting programs - the CALPGM suite of programs, XIAM, and ERHAM. The current prediction
had been obtained using ERHAM and fits the 2904 assigned transitions reasonably well. This fit,
however, fails to match several previously assigned E state transitions in the cm-wave region
that arise due to splitting from the internal motion of the methyl group. It also fails to
extrapolate and match the laboratory well beyond ~500 GHz. It is believed the fit has converged
to a non-physical local minimum and requires further refinement in order to accurate fit the
entire ground state. Observational spectra of 6 interstellar sources have been collected using
the Caltech Submillimeter Observatory (CSO). These spectra were examined for evidence of
coincidental transitions with the strongest assigned MEK lines. None were observed. However,
due to the incomplete nature of the fit for MEK it should not be ruled out as a potential
interstellar molecule.

Table of Contents

Table of Contents
1 - Introduction………………………………………………………………………………………………………………………..1
2 - O(1D) Reactions…………………………………………………………………………………………………………………..2
3 - Source Design……….…………………………………………………………………………………………………………….6
4 - Methyl Ethyl Ketone ………………………………………………………………………………………………………….10
5 - MEK Spectral Acquisition……………………………………………………………………………………………………12
6 - MEK Hamiltonian…………….…………………………………………………………………………………………………15
7 - MEK Results and Analysis…………………………………….…………………………………………………………….24
8 - Astronomical Observations ……………………………………………………………………………………………….34
9 -Conclusion…………………………………………………………………………………………………………………………..40
Sources Cited…………………………………………………………………………………………………………………………..42
Appendix A………………………………………………………………………………………………………………………………45
Figures
1 - Unstable molecules through O(1D) Insertion…………………………………………………………………….…4
2 - Fast Mixing Photolysis Supersonic Expansion Source Design…………………………………………….…6
3 - First Fast Mixing Photolysis Supersonic Expansion Source…………………………………………………...7
4 - Second Fast Mixing Photolysis Supersonic Expansion Source…………………………………………….…7
5 - New Expansion Source for Ozone Use……………………………………………………………………………..….9
6 - Interstellar Molecules Similar to Methyl Ethyl Keton………………………………………………………….10
7 - CP-FTMW Spectrometer Diagram………………………………………………………………………………………12
8 - VDI Multiplier Chain Setup and Band Coverage………………………………………………………………….14
9 - Direct Absorption Flow Cell Diagram………………………………………………………………………………….15
10 - V3 Barrier to Internal Rotation of a Methyl Group…………………………………………………………...20

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