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 shocks.
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
investigated
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.

Contributor(s): H. S. P. Müller 10, 2012; 02, 2016