Variable Temperature, Intensity Calibrated, Complete Submillimeter Spectra and Analysis for Astrophysical Assignment

Traditional spectroscopic approaches which relied on quantum mechanical assignment have left astrophysical catalogs incomplete with regards to the perturbed excited vibrational/torsional states of several astrophysically common molecular species. The result is that many of the unidentified features in astrophysical spectra are due to already identified species in an excited state. The confusion of lines due to target species and lines due to molecular `weeds’, hinders the astronomers’ ability to identify new molecules in astrophysical spectra. With the advent of powerful new telescopes this problem has been further exacerbated.This thesis describes a new approach for analyzing intensity calibrated laboratory spectra taken at many different temperatures. By analyzing these spectra together, it is possible to derive the lower state energy and transition strength for every spectral line without quantum mechanical assignment. These derived parameters can then be used to predict a complete spectrum, including the difficult to assign excited states, at astrophysically relevant temperatures. Unlike the astrophysical catalogs this approach is not limited to spectral lines. By using fitting parameters, every frequency point of laboratory data can be modeled and the entire spectral range can be predicted at an arbitrary temperature.This approach was developed, tested and refined while studying eight astrophysical `weeds’ in two frequency regions. In ethyl cyanide, vinyl cyanide and methanol, the three molecules for which rigorous analysis was completed, the lower state energies and transition strengths were determined for over 8200 currently uncataloged lines. An additional five molecules in the 210-270 GHz region have had preliminary analyses completed.Astrophysical data was obtained and compared to the complete spectra predicted from this analysis. The results yielded excellent matches for methyl cyanide, ethyl cyanide and vinyl cyanide including isotopologues and uncataloged excited vibrational states.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Physics

Grantor dc:publisher

The Ohio State University

Year dc:date

2013

Author dc:creator

• Fortman, Sarah M.

Contributors dc:contributor

• De Lucia, Frank C.

• Physics
• submillimeter spectroscopy
• astrophysical assignment
• molecular assignment

Statement dc:rights

• unrestricted
• This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

Language dc:language

English

Repository record dc:identifier

http://rave.ohiolink.edu/etdc/view?acc_num=osu1366123815

OAI identifier oai:identifier

oai:etd.ohiolink.edu:osu1366123815