The effect of molecular orientation in collisions of OH with CO and N-2

The effect of OH orientation on rotationally inelastic collisions of OH(X(2 )Pi) with CO and N-2 has been studied in a crossed molecular beam setup at translational energies of 750 and 690 cm(-1), respectively. The OH molecule s were prepared in the v=0,Omega = 3/2,J = 3/2,f state by hexapole state se lection and oriented with their O end or H end toward the collision partner by a static electric field in the collision zone. A degree of orientation of < cos theta > =0.46 has been obtained. In general the cross sections are larger for collisions at the O end in excitation to low rotational states, whereas the cross sections are larger for H end excitation to higher rotat ional states. OH+CO and OH+N-2 behave quite similarly when compared to OH+A r. Systematic differences between OH+CO and OH+N-2 may be attributed to the influence of complex formation on the inelastic collision process. Reanaly sis of state-to-state scattering experiments on unoriented OH+CO and OH+N-2 indicate that the interaction potential is more head-tail symmetric with r espect to OH for OH+N-2 compared to OH+CO. (C) 2001 American Institute of P hysics.