|
The hydroxymethyl radical has a fairly high barrier to
inversion of the hydroxyl group. This causes a small
splitting of order of 140 MHz. The b-dipole
moment component connects the two tuneling states;
a-type selection rules hold for pure rotational
transitions, but the magnitude of the dipole moment
component appears to be very small. With respect to
the first entry from Mar. 2017, a large body of
transition frequencies was added to the fit.
These were published by
(1) O. Chitarra, M.-A. Martin-Drumel, B. Gans, J.-C. Loison,
S. Spezzano, V. Lattanzi, H. S. P. Müller, and O. Pirali,
2020, Astron. Astrophys. 644, Art. No. A123.
Many new data were determined, data from the initial paper
remeasured, and more data from the initial paper retained
than in that initial paper, published by
(2) C. Bermudez, S. Bailleux, and J. Cernicharo,
2017, Astron. Astrophys. 598, Art. No. A9.
The data set still contains only transitions with
Ka = 1 ↔ 0. Therefore, calculations
for Ka = 2 ↔ 1 should be viewed with
great caution, even more so for transitions with higher
Ka. Caution is also advised for
transitions with calculated uncertainties exceeding
0.2 MHz.
The quantum number format of the standard entry is N,
Ka, Kc, vt,
TSP, F, where vt is the
tunneling state. vt = 0 is also designated
as v = 0+, vt = 1 is
also designated as v = 0–. TSP
is an aggregate spin number, which can be translated into
(N), J, F1, I, and
F through a
aggregate_spin_number.txt. While I is given absolute,
the other quantum numbers are given relative to
F = 0. Alternatively the file with
8 quantum numbers may be consulted.
The eight quantum numbers are N, Ka,
Kc, v, J + 0.5,
F1, Itot, and
F; J, F1, and F include
the spin-angular momenta of the electron spin, the spin of
the OH-H, and those of the two CH2-H.
At low temperatures, it may be useful to view ortho
and para states separately; they are described by
Ka + vi being even and odd,
respectively. The 11,1, J + 0.5 =
F1 = F = 2 level is the lowest
para level and is 7.352 cm–1
above ground.
The dipole moment components are from a
quantum chemical calculation by
(3) H. S. P. Müller, 2017, unpublished.
|