This H_{2}C_{3}H isomer is better described as
a combination of the 2propynyl 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
^{1}H hyperfine splitting may be
resolvable at lower frequencies and in cooler sources.
Therefore, a
calculation with hyperfine structure
is available with N and K_{a}
up to 10 and 2, respectively.
The main entry has been simplified to include only 4 quantum
numbers: N, K_{a}, K_{c},
and J + 1/2.
Since only transition with N up to 2 have been observed
the predictions have been limited to N and
K_{a} = 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
orthoH_{2}C_{3}H and
paraH_{2}C_{3}H.
The ortho states are described by K_{a} even,
the para states by K_{a} odd.
There are three times as many levels for orthoH_{2}C_{3}H
than there are for paraH_{2}C_{3}H.
Thus, for transitions with unresolved ^{1}H hyperfine splitting
the nuclear spinweight ratio is 6 : 2 between
orthoH_{2}C_{3}H
and paraH_{2}C_{3}H.
However, for transitions with resolved ^{1}H hyperfine splitting
no nontrivial spinstatistics have to be considered.
The N_{KaKc} = 1_{11};
J + 1/2 = 2 is the lowest para state.
It is 9.9103 cm^{–1} above ground.
