The third and fourth torsional states of acetaldehyde

authored by: I. Kleiner, J. T. Hougen, J. U. Grabow, S. P. Belov, M. Yu Tretyakov, J. Cosléou
Abstract: A least-squares fit is presented of 1105 far-infrared and 2860 microwave transitions in acetaldehyde, which sample rotational levels in all torsional states below the lowest-frequency small-amplitude vibration ν₁₀. Four-fifths of these transitions, involving torsional states below the barrier (υ_t ≤ 2), were treated in an earlier publication; here the theoretical model is further tested by extending the data set to include the υ_t = 3 and 4 states above the barrier. The new data set includes (i) 224 υ_t = 3 ← 2 far-infrared transitions, (ii) Nizhny Novgorod RAD-2 a-type and b-type sub millimeter transitions in υ_t = 2, which make more precise ΔΚ = ±1 intervals in this last torsional state below the barrier, (iii) RAD-3 a-type submillimeter transitions in υ_t = 3 and 4, and (iv) microwave and submillimeter measurements or remeasurements from NIST and Lille of transitions with υ_t ≤ 4. The global fit, which uses an improved version of the computer program previously applied to the υ_t ≤ 2 data, gave a weighted overall standard deviation of 1.21 with 55 adjusted and 2 fixed parameters. Residuals from the fit were close to experimental uncertainties for the infrared wavenumber measurements and for microwave and submillimeter frequency measurements below the barrier, but some residuals reached several MHz or more for frequency measurements involving levels near ν₁₀. We have attempted to achieve a qualitative understanding of the numerical results by presenting a general overview of internal rotation energy levels above the barrier and a theoretical discussion of torsion-rotation interactions among these levels.
Organisation(s): Institute of Physical Chemistry and Electrochemistry
External Organisation(s): Universite Paris 6
National Institute of Standards and Technology (NIST)
RAS - Institute of Applied Physics
Centre national de la recherche scientifique (CNRS)
Type: Article
Journal: Journal of molecular spectroscopy
Volume: 179
Pages: 41-60
No. of pages: 20
ISSN: 0022-2852
Publication date: 09.1996
Publication status: Published
Peer reviewed: Yes
ASJC Scopus subject areas: Atomic and Molecular Physics, and Optics, Spectroscopy, Physical and Theoretical Chemistry
Electronic version(s): https://doi.org/10.1006/jmsp.1996.0182 (Access: Unknown)

BibTeX

@article{40dab8cdfb4f48feb56790a2a25ffac9,
title = "The third and fourth torsional states of acetaldehyde",
abstract = "A least-squares fit is presented of 1105 far-infrared and 2860 microwave transitions in acetaldehyde, which sample rotational levels in all torsional states below the lowest-frequency small-amplitude vibration ν10. Four-fifths of these transitions, involving torsional states below the barrier (υt ≤ 2), were treated in an earlier publication; here the theoretical model is further tested by extending the data set to include the υt = 3 and 4 states above the barrier. The new data set includes (i) 224 υt = 3 ← 2 far-infrared transitions, (ii) Nizhny Novgorod RAD-2 a-type and b-type sub millimeter transitions in υt = 2, which make more precise ΔΚ = ±1 intervals in this last torsional state below the barrier, (iii) RAD-3 a-type submillimeter transitions in υt = 3 and 4, and (iv) microwave and submillimeter measurements or remeasurements from NIST and Lille of transitions with υt ≤ 4. The global fit, which uses an improved version of the computer program previously applied to the υt ≤ 2 data, gave a weighted overall standard deviation of 1.21 with 55 adjusted and 2 fixed parameters. Residuals from the fit were close to experimental uncertainties for the infrared wavenumber measurements and for microwave and submillimeter frequency measurements below the barrier, but some residuals reached several MHz or more for frequency measurements involving levels near ν10. We have attempted to achieve a qualitative understanding of the numerical results by presenting a general overview of internal rotation energy levels above the barrier and a theoretical discussion of torsion-rotation interactions among these levels.",
author = "I. Kleiner and Hougen, {J. T.} and Grabow, {J. U.} and Belov, {S. P.} and Tretyakov, {M. Yu} and J. Cosl{\'e}ou",
note = "Funding Information: The authors are indebted to Drs. R. D. Suenram and F. J. Lovas for making a number of NIST microwave measurements available before publication, and to Drs. A. R. Hight Walker and R. D. Suenram for remeasuring the troublesome ground state J 1 R 0 line at 19 265 MHz. The U.S. portion of this work was supported in part by the Division of Chemical Sciences, Office of Basic Energy Sciences, Office of Energy Research, U.S. Department of Energy; the Russian portion was supported in part by the Russian Fund for Fundamental Studies, Grant No. 94-02-05424-a, and the International Science Foundation, Grant R81000; the French portion was supported in part by the G.D.R.P.C.M.G.I. J.-U. G. was supported by a postdoctoral fellowship of the Deutsche Forschungsgemeinshaft. Calculations were carried out at the University of Paris on the IDRIS Computer Center Cray C98 and C94, and at NIST on the Cray YMP.",
year = "1996",
month = sep,
doi = "10.1006/jmsp.1996.0182",
language = "English",
volume = "179",
pages = "41--60",
journal = "Journal of molecular spectroscopy",
issn = "0022-2852",
publisher = "Academic Press Inc.",
number = "1",
}