The microwave spectrum of the fluoromethyl radical, CH2F

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Abstract
The microwave spectrum of the fluoromethyl radical, CH2F, has been observed by using a source‐frequency modulation spectrometer with a 1 m long free space absorption cell. The CH2F radical was generated directly in the cell by the reaction of methyl fluoride with 2450 MHz discharge products of CF4. The a‐type R‐branch transitions, N=1 ← 0, 2 ← 1, and 3 ← 2 for the ground vibrational state and N=2 ← 1 and 3 ← 2 for the first excited state of the out‐of‐plane bending mode (ν4), have been observed; all of them were found to be split into fine and hyperfine components, and individual lines were measured precisely. The hyperfine structure observed for the ground state is consistent with electronic symmetry of B1 and with odd parity with respect to the reflection on the ‘‘molecular plane.’’ A relative intensity measurement shows that the v4=1 state of even parity is located 300 (30) cm−1 above the ground state. These observations suggest that the CH2F molecule is essentially planar, although the presence of a small hump at the planar configuration cannot be excluded.