Submillimeter-Wave Spectroscopy of the CH₃O Radical

Researchers at the Institut des Sciences Moléculaires d’Orsay and the University of Cologne extended the laboratory rotational spectrum of the methoxy radical (CH₃O) into the submillimetre-wave region, from 350 to 860 GHz. CH₃O is an important intermediate in interstellar methanol chemistry. It was produced by hydrogen abstraction from methanol with fluorine atoms. It was detected by absorption spectroscopy combining source-frequency and Zeeman modulation. The new transitions reach higher frequencies and rotational quantum numbers than earlier work. Fitted together with literature data, they substantially refine the spectroscopic parameters, allowing reliable predictions from microwave to submillimetre wavelengths. A wire-grid polarizer at the cell entrance directed the radiation to the detector.