Microwave Spectrum of the AsD2(&Xtilde;2B1) Radical: Harmonic Force Field and Molecular Structure

The pure rotational spectrum of AsD2 in the 2B1 ground electronic state was measured in the frequency region of 268-398 GHz by microwave spectroscopy. The AsD2 radical was generated in a free-space cell by dc-glow discharge of a gaseous mixture of D2 and He over arsenic powder. Fifty fine and hyperfine components of nine rotational transitions were measured and analyzed by least-squares methods determining the detailed molecular constants of AsD2: the rotational constants, the centrifugal distortion constants, the spin-rotation coupling constant with the centrifugal distortion terms, and the hyperfine coupling constants associated with the arsenic and deuterium nuclei. The harmonic force field of AsH2 was determined from the centrifugal distortion constants, the equilibrium vibrational frequency of nu2 mode of AsH2, and the inertial defects of AsH2 and AsD2. The harmonic force field was used to calculate vibrational corrections to the rotational constants of both species and thus the zero-point average structures for both species were derived; AsH2: rz(AsH) = 1.53436(15) Å, thetaz(HAsH) = 90.695(20) degrees, and AsD2: rz(AsD) = 1.52902(13) Å, thetaz(DAsD) = 90.722(17) degrees, where the errors in parentheses are due to residual inertial defects of the corrected moments of inertia. From the difference between the rz structures for AsH2 and AsD2 the re structure of AsH2 is estimated to be re(AsH) = 1.5158(6) Å, thetae(HAsH) = 90.79(8) degrees. Copyright 1998 Academic Press.