The methoxy radical, CH3O, is a symmetric top rotor with a
doubly degenerate ground electronic state and large spin-orbit splitting.
The Ω = 3/2 spin component (J =
N + 1/2) is lower in energy than the 1/2 component.
Λ-doubling can usually be resolved for K = 0, 1,
and to some extent also for K = 1. Moreover, the
molecule exhibts complex fine and hypperfine splitting. Seven stronger
hyperfine components of the N = 1 0
(F = 2 1; Λ = 1 and
+1 near 82.6 GHz) and N = 2 1
(both Λ components for each F = 4 3
and 3 2, and the 1 component for 2 1
near 137.5 GHz) were detected in emission with reasonable to good
signal-to-noise ratio in the course of a 3 and 2 mm molecular
line survey with the IRAM 30 m radiotelescope toward B1-b.
Barnard 1 is a dark clould which is subjected to radiation or
J. Cernicharo, N. Marcelino, E. Roueff, M. Gerin, A. Jiménez-Escobar, and G. M. Muñoz Caro,
Discovery of the Methoxy Radical, CH3O, toward B1: Dust Grain and Gas-phase Chemistry in Cold Dark Clouds
Astrophys. J. 759, Art. No. L43 (2012).
A. Bacmann and A. Faure
The origin of gas-phase HCO and CH3O radicals in prestellar cores
Astron Astrophys. 587, Art. No. A130 (2016).
Transitions of the N = 1 0, Σ = +1 groups of lines were detected with the IRAM 30 m telecope in four of eight sources, L1495A-S, L1689B, L1709A, and TMC-2.