Production and magnetic analysis of beams of S atoms and SO radicals: a collisional study of their interactions with hydrogen molecules

An intense and stable continuous beam of S atoms and SO radicals has been produced with a microwave discharge source operating in the Torr range in mixtures of SO2 with various gases. The beam emerging from the plasma source was velocity analyzed by a mechanical velocity selector and detected by a quadrupole mass filter. Stern-Gerlach magnetic analysis indicates that both species are mainly generated in their electronic ground state and in the case of sulfur atoms with fine-structure levels, populated according to their degeneracies. Total integral cross section measurements are reported, as a function of velocity in the range 1.0-2.5 km x (-1), for the scattering of S(P-3(J)) atoms and SO ((3)Sigma) radicals by D-2 molecules. The analysis of experimental data (cross sections and their velocity dependence, which exhibits glory interference patterns) allows a characterization of the spherically average component of the interaction potential for the investigated systems. A discussion of the effect of the Sigma-Pi splitting, spin-orbit, and electrostatic (including quadrupole-quadrupole) interaction on the dependence of the hydrogen molecule orientation is given for the S-H-2 potential energy surface. (C) 1998 Elsevier Science B.V.