The effect of molecular orientation in collisions of OH with CO and N2

Abstract

The effect of OH orientation on rotationally inelastic collisions of OH(X2Π) with CO and N2 has been studied in a crossed molecular beam setup at translational energies of 750 and 690 cm−1, respectively. The OH molecules were prepared in the v=0,Ω=32,J=32,f state by hexapole state selection 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 〈cosθ〉=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 rotational states. OH+CO and OH+N2 behave quite similarly when compared to OH+Ar. Systematic differences between OH+CO and OH+N2 may be attributed to the influence of complex formation on the inelastic collision process. Reanalysis of state-to-state scattering experiments on unoriented OH+CO and OH+N2 indicate that the interaction potential is more head–tail symmetric with respect to OH for OH+N2 compared to OH+CO.