2-Propynyl, propargyl, ethynylmethyl, X 2B1
Species tag 039505
Date of EntryJan. 2004
ContributorH. S. P. Müller

This H2C3H isomer is better described as a combination of the 2-propynyl and the propadienyl resonance forms. These resonance forms are also known as propargyl and allenyl, respectively.
The experimental lines were taken from
(1) K. Tanaka, Y. Sumiyoshi, Y. Ohshima, Y. Endo, and K. Kawaguchi, 1997, J. Chem. Phys. 107, 2728.
The parameters used in the present fit differ slightly from those in (1).
Since the rather complex hyperfine splitting will be unresolvable at higher frequencies or hard to be resolved at lower frequencies in warmer inter- or circumstellar sources the main entry does NOT take into account hyperfine splitting. NOTE HOWEVER: the 1H hyperfine splitting may be resolvable at lower frequencies and in cooler sources. Therefore, a calculation with hyperfine structure is available with N and Ka up to 10 and 2, respectively.
The main entry has been simplified to include only 4 quantum numbers: N, Ka, Kc, and J + 1/2. Since only transition with N up to 2 have been observed the predictions have been limited to N and Ka = 30 and 6, respectively. But even for these the predicted uncertainties should be viewed with great caution !
The predictions with hyperfine splitting have six quantum numbers. In this case, the fourth quantum number is 1 for transitions with hyperfine splitting. The fifth one is an aggregate spin number. It can be decoded with part of the hfs.out file. The sixth quantum number, F, designates the total spin.
The dipole moment is from an ab initio calculation by
(2) P. Botschwina, R. Oswald, J. Flügge, and M. Horn, 1995, Z. Phys. Chem. 188, 29.
At low temperatures, it may be necessary to discern between ortho-H2C3H and para-H2C3H. The ortho states are described by Ka even, the para states by Ka odd. There are three times as many levels for ortho-H2C3H than there are for para-H2C3H. Thus, for transitions with unresolved 1H hyperfine splitting the nuclear spin-weight ratio is 6 : 2 between ortho-H2C3H and para-H2C3H. However, for transitions with resolved 1H hyperfine splitting no non-trivial spin-statistics have to be considered. The NKaKc = 111; J + 1/2 = 2 is the lowest para state. It is 9.9103 cm–1 above ground.

Lines Listed692
Frequency / GHz< 566
Max. J30
log STR0-12.0
log STR1-6.3
Isotope Corr.-0.0
Egy / cm-10.0
 µa / D0.14
 µb / D 
 µc / D 
 A / MHz288055.
 B / MHz9523.36
 C / MHz9207.20
detected in ISM/CSMno

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