Hydroxymethyl radical
Species tag 031515
Date of EntryMar. 2017
ContributorH. S. P. Müller

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. 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, Ka, Kc, v, J, F1, Itot, and F; where v refers to the tunneling state, and 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. 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 Ka + vi being even and odd, respectively. The 11,1, J = F1 = 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 Itot 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, F1, 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(2) H. S. P. Müller, 2017, unpublished.

Lines Listed6227
Frequency / GHz< 1000
Max. J34
log STR0-7.5
log STR1-5.5
Isotope Corr.-0.0
Egy / (cm–1)0.0
 µa / Dsmall
 µb / D1.47
 µc / D 
 A / MHz194541.
 B / MHz29843.2
 C / MHz25946.7
detected in ISM/CSMno

Database maintained by Holger S. P. Müller and Sven Thorwirth, programming by D. Roth and F. Schloeder