CaC4H
Calcium monodiacetylide, X 2Σ+
Species tag 089507
Version1*
Date of EntryJun. 2026
ContributorH. S. P. Müller

The Fourier transform Microwave data were taken from
(1) T. Gur, P. B. Changala, J. H. Baraban, M. C. McCarthy, 2025, J. Phys. Chem. A 129, 11531.
Hyperfine structure (HFS) splitting caused by the 1H nucleus may be resolvable for low N transitions. Therefore, a separate hyperfine calculation is provided for J ≤ 7 below 14 GHz and with somewhat lowered intensity cut-offs. NOTE: The partition function takes into account the spin multiplicity of the 1H nucleus !
The calculated transition frequencies should be quite reliable up to about 70 GHz.
The dipole moment was taken from a quantum chemical calculation in (1).

Lines Listed120
Frequency / GHz< 120
Max. J60
log STR0-10.0
log STR1-4.3
Isotope Corr. 
Egy / cm–10.0
 µa / D1.37
 µb / D 
 µc / D 
 A / MHz 
 B / MHz987.477
 C / MHz 
 Q(300.0)25337.6362
 Q(225.0)19000.6820
 Q(150.0)12665.6485
 Q(75.00)6332.5333
 Q(37.50)3166.6943
 Q(18.75)1583.9545
 Q(9.375)792.6300
 Q(5.000)423.3563
 Q(2.725)231.3381
detected in ISM/CSMno


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