With respect to the Jan. 2003 entry, very accurate
(Lambdip) 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 highK 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
D_{K} to be determined.
The data have been subjected to a combined fit with the
ν_{10} band data and the v_{10} = 1
pure rotational data from (3) and references therein.
The interactions of v_{10} = 1 with
v_{9} = 1 and v_{10} = 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
ACH_{3}CCH and ECH_{3}CCH.
The A state levels are described by K = 3n,
those of E state by K = 3n ± 1.
The nuclear spinweight ratio is 2 : 1 for ACH_{3}CCH
with K > 0 and all other states, respectively.
The J_{K} = 1_{1} 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 v_{10} = 1,
v_{9} = 1, and v_{10} = 2.
Their respective contributions are given in parentheses as long
as they are different from 0 within the quoted digits.
