Progress In Understanding The Infrared Spectra Of He- And Ne-c2d2

McKellar, Bob

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https://hdl.handle.net/2142/50769 Copy

Description

Title

Progress In Understanding The Infrared Spectra Of He- And Ne-c2d2

Author(s)

McKellar, Bob

Contributor(s)

Moazzen-Ahmadi, Nasser

Issue Date

2014-06-20

Keyword(s)

Clusters/Complexes

Abstract

"Infrared spectra of He-C$_2$H$_2$ were recorded around 1990 in Roger Miller's lab, but detailed rotational assignment was apparently not possible even with the help of theoretical predictions. So there were no published experimental spectra of helium-acetylene van der Waals complexes until our recent work on He-C$_2$D$_2$ in the \nub{3} region ($\sim$2440 \wn).\footnote{M. Rezaei, N. Moazzen-Ahmadi, A.R.W. McKellar, B. Fernández, and D. Farrelly, Mol. Phys. \textbf{110}, 2743 (2012).} The problem is that this complex lies close to the free rotor limit, so that most of the intensity in the spectrum piles up in tangles of closely spaced lines located close to the monomer rotational transitions, $R(0)$, $P(1)$, etc. Our previous He-C$_2$D$_2$ assignments were limited to the $R(0)$ region, that is, the $j$ = 1 $\leftarrow$ 0 subband, where $j$ represents C$_2$D$_2$ rotation. Here, we extend the analysis to $j$ = 0 $\leftarrow$ 1 and 2 $\leftarrow$ 1 transitions with the help of new spectra obtained using a tunable OPO laser probe and a cooled supersonic jet nozzle. These subbands are weaker, not only because of the Boltzmann factor, but also the 2:1 nuclear spin statistics of $j""$ = even:odd C$_2$D$_2$ levels. Moreover, the $j$ = 0 $\leftarrow$ 1 subband is overlapped by strong (C$_2$D$_2$)$_2$ transitions. We use a term value approach, obtaining a self-consistent set of ``experimental"" energy levels which can be directly compared with theory or fitted in terms of a Coriolis model. Challenges also arise with Ne-C$_2$D$_2$, which is not quite so close to the free rotor limit, but still has many overlapping lines. Insights gained here help in assigning the tricky $R(1)$ region for Ne-C$_2$D$_2$."

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

English

Permalink

http://hdl.handle.net/2142/50769

DOI

https://doi.org/10.15278/isms.2014.FB08

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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