| Popis: |
We have extended to higher frequency our earlier assignments ( J. Mol. Spectrosc. 162, 142–151, 1993) of the dense rotation–torsion structure in the G s methyl rocking infrared fundamental band of dimethylacetylene (CH 3 CCCH 3 or 2-butyne) centered at about 1036 cm −1 . The E 2 d combination band ν 4 + ν 16 at 1057 cm −1 significantly perturbs this high-frequency structure, and we include its effect explicitly in the Hamiltonian matrix. We can now include considerably more of the high-frequency data in the analysis, and the new fitting leads to a determination of the ground state torsional potential parameter V 3 as 1.517 cm −1 , and a torsional barrier height (4 V 3 + 4 V 9 ) of 5.98 ± 0.03 cm −1 . We cannot reproduce satisfactorily the structure in the immediate vicinity of the perturbation because of our lack of data for the ν 4 + ν 16 perturbing state. |
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