CH3CCH, v = 0
Propyne, methylacetylene, v = 0
Species tag 040502
Date of EntryAug. 2008
ContributorH. S. P. Müller

With respect to the Jan. 2003 entry, very accurate (Lamb-dip) transition frequencies up to 717 GHz as well as additional accurate lines between 1.0 and 1.2 THz have been published by
(1) G. Cazzoli and C. Puzzarini, 2008, Astron. Astrophys. 487, 1197.
Additional high-K lines between 509 and 715 GHz as well as transition frequencies betwen 765 and 922 GHz were taken from
(2) H. S. P. Müller, S. Thorwirth, L. Bizzocchi, and G. Winnewisser, 2000, Z. Naturforsch. 55a, 491; and
(3) H. S. P. Müller, P. Pracna, and V.-M. Horneman, 2002, J. Mol. Spectrosc. 216, 397.
Ground state combination loops in (3) permit A and DK to be determined. The data have been subjected to a combined fit with the ν10 band data and the v10 = 1 pure rotational data from (3) and references therein. The interactions of v10 = 1 with v9 = 1 and v10 = 2, as described in (3), have been taken into account.
Experimental lines with uncertainties larger than 100 kHz have not been merged because of the many lines with smaller uncertainties.
The dipole moment is from
(4) P. M. Burrell, E. Bjarnov, and R. H. Schwendeman, 1980, J. Mol. Spectrosc., 82, 193.
At low temperatures, it may be necessary to discern between A-CH3CCH and E-CH3CCH. The A state levels are described by K = 3n, those of E state by K = 3n ± 1. The nuclear spin-weight ratio is 2 : 1 for A-CH3CCH with K > 0 and all other states, respectively. The JK = 11 level is the lowest E state level. It is 5.5933 cm–1 above ground.
Besides the ground vibrational state, the partition function takes into account the states v10 = 1, v9 = 1, and v10 = 2. Their respective contributions are given in parentheses as long as they are different from 0 within the quoted digits.

Lines Listed1958
Frequency / GHz< 1892
Max. J111
log STR0-9.7
log STR1-9.7
Isotope Corr.-0.0
Egy / (cm–1)0.0
 µa / D0.784
 µb / D 
 µc / D 
 C = B
 Q(300.0)17826.0720 (4518.3010; 1040.8925, 1412.0356)
 Q(225.0)9357.5685 (1740.3447; 245.6071, 322.7121)
 Q(150.0)4209.3392 (333.2663; 17.6501; 21.7571)
 Q(75.00)1362.3596 (5.1339; 0.0144; 0.0146)
 Q(37.50)481.7197 (0.0035)
detected in ISM/CSMyes

Database maintained by Holger S. P. Müller and Sven Thorwirth, programming by D. Roth and F. Schloeder