The infrared spectrum of diacetylene

• Published in: Journal of molecular spectroscopy Vol. 76; no. 1; pp. 492 - 505
• Main Authors: Hardwick, J.L., Ramsay, D.A., Garneau, J.-M., Lavigne, J., Cabana, Aldée
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.01.1979
• ISSN: 0022-2852; 1096-083X
• DOI: 10.1016/0022-2852(79)90237-6

The spectrum of diacetylene has been investigated with high resolution in both the infrared and photographic infrared regions. Bands at 628, 1241, 9609, and 9717 cm −1 have been rotationally analyzed for the first time, and bands at 8578, 8744, and 9684 cm −1 have been reinvestigated with higher resolution than in earlier work. Improved rotational constants have been obtained for the ground state, viz., B″ 0 = 0.14640 6 ± 0.00002 cm −1 and D″ 0 = (1.0 ± 1.0) × 10 −8 cm −1. The error limits are dominated by systematic errors rather than statistical errors and are dependent on the general lack of resolution of the “cold” bands from the underlying “hot” bands. Molecular constants have been derived for several vibrational levels. In particular, the l-type doubling in the ν 9 level has been shown to be smaller than in earlier work. The rotational constants for the ν 7 level have been accordingly revised. Accurate molecular constants for the ν 8 level are reported for the first time. The new data permit predictions of the frequencies of the ( ν 8− ν 6) difference band, which lies in the microwave region of the spectrum. The ( ν 6 + ν 8) combination band at 1241 cm −1 is unusually strong and may serve as a useful probe for diacetylene in astrophysical sources.