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The experimental lines were taken from
(1) W. Chen, M. C. McCarthy, M. J. Travers, E. W. Gottlieb,
M. R. Munrow, S. E. Novick, C. A. Gottlieb, and P. Thaddeus,
1998, Astrophys. J. 492, 849;
and from
(2) J. Tang, Y. Sumiyoshi, and Y. Endo,
2001, Astrophys. J. 552, 409.
Because of the limited quantum number range of the experimental
data, predictions for
Ka = 2 should be viewed with caution.
Transitions with even higher Ka have been
omitted from the predictions. Similarly, predictions with
N about 20 or higher should be viewed with caution.
Since the rather complex hyperfine splitting, which was resolved
in the laboratory measurements, 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: both the
1H and 14N hyperfine splitting may be
resolvable at lower frequencies and in cooler sources.
Therefore, a
calculation with hyperfine structure
is available with N" up to 20.
The predictions with hyperfine splitting have all quantum numbers.
The fourth one is an
aggregate spin number.
It can be decoded with part of the
hfs.out file.
The fifth quantum number, F, designates the total spin.
The main entry has been simplified to include only 4 quantum
numbers: N, Ka, Kc,
and J + 1/2. The partition function and the upper state
degeneracies of the hyperfine free entry
take into account the hyperfine splittin !
The dipole moment is from an ab initio calculation in (2).
At low temperatures, it may be necessary to discern between
ortho-H2C4N and
para-H2C4N. The ortho states
are described by Ka even, the para states
by Ka odd. There are three times as many levels
for ortho-H2C4N than there are for
para-H2C4N. Thus, for transitions with
unresolved 1H hyperfine splitting, the nuclear spin-weight
ratio is 9 : 3 between ortho-H2C4N
and para-H2C4N. 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 9.67 cm–1 above ground.
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