Torsion-rotation-vibration Effects In The V20, 2v21, 2v13 And V21+v13 States Of Ch3ch2cn

Daly, Adam M

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https://hdl.handle.net/2142/51207 Copy

Description

Title

Torsion-rotation-vibration Effects In The V20, 2v21, 2v13 And V21+v13 States Of Ch3ch2cn

Author(s)

Daly, Adam M

Contributor(s)

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

Issue Date

2014-06-19

Keyword(s)

Mini-symposium: Astronomical Molecular Spectroscopy in the Age of ALMA

Abstract

Ethyl cyanide, CH$_{3}$CH$_{2}$CN, is a highly abundant molecule in hot cores associated with massive star formation where temperatures often approach 200 K. Astrophysicists would like to use the many thousands of observed lines to evaluate thermal equilibrium, temperature distributions, heating sources, and radiative pumping effects. In spite of a recent partial success in characterizing the v$_{20}$ and v$_{12}$ vibrational states$^{a}$, many aspects of the spectroscopy of the v$_{20}$ state are not adequately characterized. Torsional splittings in the b-type spectrum of v$_{20}$ are typically a few MHz and many a-type transitions also show resolved torsional splittings, both are incompatible with the expected 1200 cm$^{-1}$ barrier to internal rotation in a v$_{t}$ = 0 state. Additionally all K values above 2 show some obvious perturbations. The three states that lie just above v$_{20}$ are 2v$_{21}$, 2v$_{13}$ and v$_{21}$ + v$_{13}$. It has been determined that v$_{20}$ interacts weakly with both 2v$_{21}$ and 2v$_{13}$ and that 2v$_{21}$ interacts weakly with 2v$_{13}$, in spite of their common symmetry and very close proximity. However, all the interactions of v$_{21}$ + v$_{13}$ appear to be very strong, making assignments of the combination band particularly problematic. The numerous interactions result in wide spread anomalous torsional splittings. These splittings provide valuable insight into the nature of the interactions, however without a reasonable model, assignment of A or E to a torsional component is far from obvious. There remains no reasonable quantum mechanical description of how to proceed with a torsion-rotation-vibration analysis involving large and small amplitude motions. We present what is known and unknown in this quartet of CH$_{3}$CH$_{2}$CN states. $^{a}$Daly, A. M., Berm\'{u}dez, C., L\'{o}pez, A., et al., 768, 1, ApJ, 2013

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

English

Permalink

http://hdl.handle.net/2142/51207

DOI

https://doi.org/10.15278/isms.2014.RA04

Copyright and License Information

Copyright 2014 by the authors. Licensed under a Creative Commons Attribution 4.0 International License. http://creativecommons.org/licenses/by/4.0/

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