Submillimetre-wave spectra of AsH and AsD radicals in the X3Σ- electronic state

Abstract

Rotational lines of AsH and AsD radicals in their X ³ Σ ^- ground state have been observed in the submillimetre-wave region for the first time. The AsH radical was generated by dc-glow discharge in pure AsH ₃ gas, and the AsD radical was generated by the reaction of arsenic powder with a mixture of D ₂ and O ₂ gases in a dc-glow discharge. Three rotational transitions of AsH with hyperfine structure (N,J=0,1–1,0 2,1–1,1 3,2–2,2) were measured in the frequency region 120–338 GHz, and five transitions(N,J=0,1–1,0 2,1–1,0 2,2–1,1 4,3–3,3 5,4–4,4) of AsD in the region 173–440 GHz. The molecular constants, including the rotational constants, the spin–rotation coupling constant with the centrifugal distortion term and hyperfine coupling constants associated with the arsenic, hydrogen and deuterium nuclei, were precisely determined by least-squares fitting to the observed spectral lines. Using the results of both AsH and AsD, the Born–Oppenheimer equilibrium bond length was derived, where the adiabatic correction was taken into account: r _e ^BO =1.522370 (86) Å.