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

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Abstract
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 k 2=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.