The microwave spectrum of a new phosphorus-bearing radical CH2P(2B2)

Abstract

The microwave spectrum of the CH2P radical in its B22 ground electronic state was detected for the first time using a source-modulated spectrometer equipped with a free-space cell. The CH2P radical was generated in the cell by a dc-glow discharge in a mixture of PH3, CH4, and He, and its isotopic species, CD2P, in a mixture containing CD4 instead of CH4. Forty four a-type R-branch rotational transitions of CH2P were measured for the transitions N=8–7 to N=12–11 with Ka=0 to 5 in the frequency region of 260–400 GHz, for which fine and hyperfine structures due to the phosphorus and hydrogen nuclei were resolved. For CD2P, 39 rotational transitions from N=9–8 to N=13–12 with Ka=0 to 4 were measured in the 240–355 GHz with fine structure and phosphorus hyperfine structure. Molecular constants of CH2P, including the fine structure constants and hyperfine coupling constants due to both the nuclei of P and H, were precisely determined by least-squares methods from 158 observed spectral lines. Those of CD2P were similarly obtained from 70 observed spectral lines. The rotational constants of both species were used to derive the molecular structural parameters for CH2P: r0(CP)=1.6576(28) Å, r0(CH)=1.0912(61) Å, and ∠HCH=115.96(96)°. The spin densities of unpaired electrons on the P and H nuclei were estimated from the hyperfine coupling constants, and found to be consistent with the molecular structure determined.