UPDATE OF THE ANALYSIS OF THE PURE ROTATIONAL SPECTRUM OF EXCITED VIBRATIONS OF CH3CH2CN

Daly, Adam M

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https://hdl.handle.net/2142/79486 Copy

Description

Title

UPDATE OF THE ANALYSIS OF THE PURE ROTATIONAL SPECTRUM OF EXCITED VIBRATIONS OF CH3CH2CN

Author(s)

Daly, Adam M

Contributor(s)

• Alonso, José L.
• Bermúdez, Celina
• Drouin, Brian
• Yu, Shanshan
• Pearson, John

Issue Date

23-Jun-15

Keyword(s)

Large amplitude motions, internal rotation

Abstract

The torsion-vibration-rotation analysis of nearly degenerate vibrational states involving both small and large amplitude motion has escaped satisfactory quantum mechanical description. Unfortunately the interstellar medium is filled with many prevalent molecules that feature internal rotation that couples strongly with torsional bath states. Many excited states are observed in emission in hot cores associated with massive star formation and it is likely that absorption in the infrared will be seen by JWST. We present our progress on the analysis of the high resolution pure rotational spectrum of ethyl cyanide, CH$_{3}$CH$_{2}$CN, which is highly abundant in hot cores with massive star formation and can serve as a sensitive temperature and source size probefootnote{A.M. Daly, C. Bermﾜdez, A. Lﾗpez, B. Tercero, J.C. Pearson, N. Marcelino, J.L. Alonso, J. Cernicharo textit{Astrophys. J.}, textbf{768} 81 (2013)}. Although the ground state has been assigned to 1.6 THzfootnote{C.S. Brauer, J.C. Pearson, B.J. Drouin, S. Yu textit{ApJ Suppl. Ser.}, textbf{184} 133 (2009)}, the two vibrational states nub{13} and nub{21}, the C-C-N bend and torsion, have only been assigned up to 400 GHzfootnote{D.M. Mehringer, J.C. Pearson, J. Keene, T.G. Phillips textit{Astrophys. J.}, textbf{608} 306 (2004)}. It is clear that detailed understanding of excited states will help properly model the temperature dependence of the intensity. We will report the progress on the fit up to 1.5 THz for the states nub{13} , nub{21} , nub{20} and nub{12}, at 206.5 wn, 212 wn, 375 wn and 532 wn respectively. In spite of a nearly 1200 wn barrier to internal rotation all the vibrational states observed feature A/E splittings inconsistent with such a high barrier suggesting that there is extensive coupling between the torsional bath states and the excited vibrations. The low lying states of ethyl cyanide provide an opportunity to assess all the possible interaction under the C$_{S}$ group for both A and E symmetry in the high barrier case to serve as a benchmark for developing theory for the analysis of lower barrier cases.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

English

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http://hdl.handle.net/2142/79486

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