Molecular Beam Kinetics: Magnetic Deflection Analysis of Scattering of Alkali Atoms from Polyhalide Molecules

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Abstract
An inhomogeneous magnetic field has been used to measure the ratio of reactively scattered alkali halide molecules (diamagnetic) to elastically scattered alkali atoms (paramagnetic) for several systems, including Cs + Br2, CH3I, CHCl3, CCl4, SiCl4, and SnCl4; K + CC14 and SiCl4; and Na + CH3I. For comparison, the scattering of the nonreactive systems Cs+cyclohexane and Na+propane was also studied. The results verify previous work which employed two surface ionization filaments to distinguish between reactive and elastic scattering. In particular, it is confirmed that the laboratory angular distribution of KCl from the K + CCl4 reaction is bimodal. To enhance the alkali beam intensity, a “Laval slit” was used and the oven operated at pressures well above the effusive flow region. This source produces marked deviations from the Maxwell–Boltzmann velocity distribution. It was found that the Stern–Gerlach deflection patterns and the variation of transmission with field strength for such beams can be accurately calculated by use of a suitable modification of the velocity distribution (empirically calibrated in separate velocity‐analysis experiments).