The 2A1–2E electronic spectrum of methoxy, CH3O: Vibrational progressions, and spin-orbit and Jahn–Teller couplings

The 310 nm electronic emission system of jet-cooled methoxy radical has been examined at 4 cm−1 resolution. The spectrum shows extensive progressions in the upper and lower state CO stretch frequencies, v′3 =660±2 cm−1 and v″3 =1045±3 cm−1. Two other lower state frequencies have been determined: the hydrogen stretch v″1 =2749±5 cm−1 and the hydrogen scissors v″5 =1499±6 cm−1. The Jahn-Teller effect activates v″5 with a coupling constant of k2=0.28±0.06, but does not appreciably activate either v″4 or v″6. The corresponding frequencies have been observed in deuterated methoxy. The change in the spin-orbit splitting upon deuteration, dropping from 62 to 56 cm−1, indicates that the purely electronic spin-orbit splitting is 98±11 cm−1, while the vibronic reduction factor in the hydride is 0.63±0.06.