A NEW PHOSPHORUS BEARING DERIVATIVE OF THE METHYL RADICAL, CH2CP, STUDIED BY MICROWAVE SPECTROSCOPY AND AB-INITIO CALCULATION

The microwave spectrum of the CH2CP radical in its B-2(1) ground elect ronic state was detected for the first time using a source-modulated m icrowave spectrometer. The radical was generated in the cell by a dc-g low discharge in a mixture of PH3 and C2H2. Fine structure was observe d but no hyperfine structure pertaining to the phosphorus and hydrogen nuclei could be resolved. In total 110 spectral lines were measured f or the K-structure and fine structure of eight rotational transitions in the 300-380 GHz region. The rotational, centrifugal distortion, and spin-rotation coupling constants were obtained by a least-squares ana lysis of the measured frequencies. On the basis of accompanying couple d cluster calculations an accurate equilibrium structure could be esta blished; r(e)(CH) = 1.0816(5) Angstrom, alpha(e)(HCH) = 118.22(5)degre es, R-1e(CC) = 1.3418(10) Angstrom, and R-2e(CP) = 1.5889(10) Angstrom . The equilibrium dipole moment is predicted to be mu(e) = - 1.15 D, w ith the negative end at the phosphorus site. (C) 1998 American Institu te of Physics.