Rotational polarization of reaction products analysis of electric deflection profiles

Abstract

In molecular beam experiments the preferred spatial orientation or polarization of the rotational angular momentum of reactively scattered molecules can be determined by deflection in an inhomogeneous electric field. The apparatus, experimental method, and analysis procedure are described and illustrated with data obtained for the K + HBr, Cs + HBr, and Cs + HI reactions. The experiments employ a new field design which eliminates the non-adiabatic change of quantization axis that handicapped a previous polarization study. A simple normalization procedure provides ‘reduced deflection profiles’ which are very insensitive to substantial variations in the experimental parameters, including the deflection field strength, beam position in the field, collimating slit widths, dipole moment, and distributions of rotational and translational energy. These reduced profiles yield <cos² x> and <cos⁴ x>, the first two moments of the probability distribution of polarization, where x is the angle between the rotational angular momentum and the initial relative velocity vector. The experimental results indicate marked polarization, corresponding to <cos² x> < 0·10, and agree well with theoretical moments calculated from a statistical phase-space treatment.