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The Perpendicular C–H Stretching Band ν9/ν13and the Torsional Potential of Dimethylacetylene

✍ Scribed by J. Plı́va; A.S. Pine; S. Civiš

Publisher
Elsevier Science
Year
1996
Tongue
English
Weight
352 KB
Volume
180
Category
Article
ISSN
0022-2852

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✦ Synopsis

The perpendicular band of the fourfold degenerate C-H stretching vibration of dimethylacetylene (2-butyne) occurring in the region 2955-3065 cm 01 has been measured with Doppler-limited resolution at a temperature of Ç195 K on a difference-frequency laser spectrometer, and on a high-resolution Fourier transform instrument at room temperature as well as in a molecular jet at Ç20 K. From a detailed rotational analysis of this complex band, based on an extension of the model of the rotational-torsional interactions described by P. R. Bunker and C. di Lauro (Chem. Phys. 190, 159-169, 1995), accurate spectroscopic constants were determined for the upper CH stretching state, along with values for the first three components of the Fourier expansion for the torsional potential in the ground state, and for six components of this potential in the upper state. Over 700 lines assigned to 37 well-resolved subbands plus 25 additional unresolved line-like Q-branches were fitted with an overall standard deviation of 0.0024 cm 01 . The results yield a value of 6.316 { 0.034 cm 01 for the barrier to internal rotation in the ground state, and 6.643 { 0.006 cm 01 for the C-H stretching state. This value for the ground state barrier is somewhat higher than that recently determined from an analysis of the CH 3 rocking band by P. R.

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