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The first entry of Dec. 2009 was improved considerably.
It now comprises 13CH3CN data in
v = 0 along with v8 = 1 and 2,
see also e042513.cat and e042540.cat.
The fit is described in
(1) H. S. P. Müller, A. Belloche, F. Lewen, and S. Schlemmer,
2026, ACS Earth Space Chem. 10, 578.
In the case of v = 0,
the line list includes new measurements employing a sample
highly enriched in CH313CN.
These are transitions with (partially) resolved 14N
hyperfine structure (HFS) splitting between 36 and 111 GHz
along with transitions without HFS splitting between
365 and 1082 GHz. Retained in the fit were data from
(2) H. S. P. Müller; B. J. Drouin, and J. C. Pearson,
2009, Astron. Astrophys. 506, 1487.
This work provides data between 312 and 1192 GHz
obtained from samples in natural isotopic composition.
Also retained in the fit were data from
(3) J. C. Pearson and H. S. P. Müller,
1996, Astrophys. J. 471, 1067;
with data from 294 to 607 GHz along with the HFS split
ground rotational transition frequencies near 18389 MHz;
and finally the HFS split J = 2 – 1 transition
frequencies near 36.8 GHz from
(4) S. G. Kukolich,
1982, J. Chem. Phys. 76, 97.
The experimental line lists
with hyperfine splitting as well as
without hyperfine splitting can be accessed with source codes.
Please note that the quantum numbers or their format have been
adjusted slightly with respect to the initial line file
for simplicity and consistency reasons.
Transition frequencies may occur for some transitions multiple times.
Vibrational identifiers in this and related entries are
0 for v = 0,
2 for v8 = 1, l = –1,
3 for v8 = 1, l = +1,
6 for v8 = 2, l = 0,
7 for v8 = 2, l = +2,
8 for v8 = 2, l = –2.
The purely K-dependent terms A and
DK were assumed to agree with
those of the main isotopolog, see e041505.cat.
The transition frequencies should be viewed with caution
if the calculated uncertainties exceed 0.1 MHz.
Please note that K = 14 may be perturbed around
J of about 90 caused by a resonant interaction with
K = +12 of v8 = 1.
14N hyperfine splitting may be resolvable
at low values of J and possibly at the highest
K. Therefore, a calculation
with hyperfine splitting is provided up to
J' = 14 (258 GHz).
Please note that the partition function does include now
the spin-multiplicities of 14N !
Please pay attention to the upper state degenercies.
The partition function values below refer to the ground
vibrational state only.
Vibrational correction factors have been derived
in the harmonic approximation.
At low temperatures, it may be necessary to discern between
A-CH313CN and
E-CH313CN.
The A state levels are described by
K = 3n, those of E state
by K = 3n ± 1.
The nuclear spin-weight ratio is 2 : 1 for
A-CH313CN with
K > 0 and all other states, respectively.
The JK = 11
level is the lowest E state level.
It is 5.5802 cm–1 above ground.
The dipole moment was assumed to agree with
that of the main isotopolog, see e041505.cat.
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