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 bdipole moment
component connects the two tuneling states;
atype selection rules hold for pure
rotational transitions, but the magnitude of
the dipole moment component appears to be
very small. The present experimental data
were published by
(1) C. Bermudez, S. Bailleux, and J. Cernicharo,
2017, Astron. Astrophys. 598, Art. No. A9.
The spectroscopic parameter set differs slightly
from that in (1). The eight quantum numbers are
N, K_{a}, K_{c}, v,
J, F_{1}, I_{tot}, and
F; where v refers to the tunneling state, and
J, F_{1}, and F include the
spinangular momenta of the electron spin, the spin of
the OHH, and those of the two CH_{2}H.
The experimental line list is somewhat limited,
therefore, predictions should be viewed with some
caution throughout, but especially if the calculated
uncertainties exceed 200 kHz.
At low temperatures, it may be useful to view
ortho and para states separately;
they are described by K_{a} +
v_{i} being even and odd,
respectively. The 1_{1,1},
J = F_{1} = F = 1.5
level is the lowest para level and is
7.351 cm^{–1} above ground.
20 Dec. 2017: please note:
Of the 8 quantum numbers, only I_{tot} can
be considered redundant. Therefore, the entry has been
recalculated with 6 quantum numbers, where the fifth is an
aggregate spin number TSP. Information on the conversion
of TSP to (N), J, F_{1},
I, and F is available in the file
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 dipole moment components are from a
quantum chemical calculation by
(2) H. S. P. Müller, 2017, unpublished.
