Differential cross section for rotationally inelastic scattering of vibrationally excited NO(v=5) from Ar

摘要

Rotationally inelastic scattering of vibrationally excited NO(v=5) from Ar was studied with a crossed molecular beam ion-imaging apparatus.Vibrationally excitd NO was generated at the exit of a pulsed nozzle by the photoinitiated reaction between O(~1D0 and N_2O.The results for rotational excitation in vibrationally excited NO were compared to those in the vibrational ground state at a collision energy of 1460 cm~(-1).The final rotational stage of NO,poulated by scattering from Ar,was detected by 1+1 REMPI via the A(~2sum~+)<-X(~2II_(1/2) electronic transition.TheR_(21) transition was used to probe the final scattered state in both cases.The rotational rainbow maxima are observed at slightly smaller angles in thescattering of vibrationally excited NO from Ar compared to the scattering of NO inthe vibrational ground state from Ar.A hard-ellipse potential model was used to investigate theeffect of initial vibrational excitation on the rotational energy-transfer process.The small shifts observedin the rainbow maxima are evidence for a slight enhancement in angular anisotropy in the intermolecular potential for NO(v=5)/Ar compared to that for NO(v=0)/Ar.