CCH, 2 IR band
Ethynyl, 5ν2 IR band
Species tag 025510
Date of EntryJuly 2010
ContributorH. S. P. Müller

The present entry combines rotational and rovibrational data of several low-lying states. Ground state transitions were taken from
(1) H. S. P. Müller, T. Klaus, and G. Winnewisser, 2000, Astron. Astrophys. 357, L65;
(2) M. Padovani, C. M. Walmsley, M. Tafalla, D. Galli, and H. S. P. Müller, 2009, Astron. Astrophys. 505, 1199;
and from
(3) K. V. L. N. Sastry, P. Helminger, A. Charo, E. Herbst, and F. C. DeLucia, 1981, Astrophys. J. 251, L119.
See for comments on these data.
The v2 = 1 rotational lines were taken from
(4) D. R. Woodward, J. C. Pearson, C. A. Gottlieb, M. Guélin, and P. Thaddeus, 1987, Astron. Astrophys. 186, L14.
Data for v2 = 2, v3 = 1, and for v2 = v3 = 1 were published in
(5) T. C. Killian, C. A. Gottlieb, and P. Thaddeus, 2007, J. Chem. Phys. 127, Art. No. 114320.
ν3 infrared transitions were measured by
(6) H. Kanamori, K. Seki, and E. Hirota, 1987, J. Chem. Phys. 87, 73.
Data for the ν2 + ν3 band were given in
(7) K. Kawaguchi, T. Amano, and E. Hirota, 1988, J. Mol. Spectrosc. 131, 58.
Transitions for 5ν2 and the hot bands 5ν2 – ν2 and ν2 + ν3 – ν2 were published by
(8) H. Kanamori and E. Hirota, 1988, J. Chem. Phys. 89, 3962.
Additional spectroscopic parameters of states up to 2200 cm–1 were taken from
(9) Y.-C. Hsu, J.-M. Lin, D. Papoušek, and J.-J. Tsai, 1993, J. Chem. Phys. 98, 6690;
(10) Y.-C. Hsu, Y.-J. Shiu, and C.-M. Lin, 1995, J. Chem. Phys. 103, 5919;
(11) W.-Y. Chiang, Y.-C. Hsu, 1999, J. Chem. Phys. 111, 1454
or have been estimated from these data.
NOTE: STR1 has been chosen to keep the amount of transitions small which have uncertainties larger than 999.9999 MHz or 0.03336 cm–1. State number 0 refers to the ground vibrational state, state number 1 to the excited vibrational state.
The anharmonic interaction between v2 = v3 = 1 and v2 = 5 can only be accounted for approximately using simple assumptions and has thus been ignored as in (8). As hyperfine structure data are available for some states it has been ignored in the energy file. This leads to small differences for the partition function values which can be neglected. Different l-components of a given vibrational state have been treated separately but will appear in the same entry as far as appropriate. Partition function values for only the ground vibrational state are given in parentheses. The partition function values are reliable up to 300 K, quite reasonable up to 500 K, and should be viewed with great caution at higher temperatures.
Predictions with uncertainties larger than 60 MHz or 0.002 cm–1 should be viewed with caution.
The dipole moment is from an ab initio calculation by
(12) D. E. Woon, 1995, Chem. Phys. Lett. 244, 45.
It is assumed that vibrational changes are negligible; this may be incorrect. Transition dipole moments were estimated from calculated infrared intensities published by
(13) R. Tarroni and S. Carter, 2004, Mol. Phys. 102, 2167.

Lines Listed146
Frequency / GHz< 66699
Max. J25
log STR0-100.0
log STR1-6.7
Isotope Corr.-0.0
Egy / (cm–1)0, 2164.8
 µa / D0.079
 µb / D 
 µc / D 
 B43674.52, 43493.
 Q(1000.)9027.3122 (1914.1407)
 Q(500.0)2085.3195 (956.6166)
 Q(300.0)815.4124 (574.2378)
 Q(225.0)520.4986 (430.9381)
 Q(150.0)304.5078 (287.6888)
 Q(75.00)144.7246 (144.4919)
 Q(37.50)72.9146 (72.9146)
 Q(18.75)37.1437 (37.1437)
 Q(9.375)19.2835 (19.2835)
 Q(5.000)10.9935 (10.9935)
 Q(2.725)6.7735 (6.7735)
detected in ISM/CSMno

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