Tensor polarizabilities of the 4f 7(8 S)5d6s 2 9 D 2,3,4,5,6 levels in Gd I

The optical pumping method with rf detection and the nonlinear level crossing technique were used in parallel electric and magnetic fields to investigate the Stark splitting of all the fine structure levels of the ground multiplet 4f ⁷ (⁸ S) 5d6s ^{2 9} D in Gd I. The tensor polarizabilities were deduced from the level crossing and the rf signals. The variation of the tensor polarizabilities is well reproduced by the LS coupling approximation, except for the small value of the⁹ D ₅ level. A value of the tensor polarizability of the 5d electron is evaluated from the experimental results, ₂(5d)=2.00(6) kHz(kV/cm)². It is shown that the ratio between the electric quadrupole constant and the tensor polarizability is constant, except for the⁹ D ₅ ratio, which is caused by a breakdown of the central field model.     

Kinetics of the BrO + NO2 association reaction. Temperature and pressure dependence in the falloff regime

A laser flash photolysis-long path absorption technique has been employed to study the kinetics of the reaction products as a function of temperature (248–346 K), pressure (16–800 torr), and buffer gas identity (N₂, CF₄). The reaction is found to be in the falloff regime between third and second-order over the entire range of conditions investigated. This is the first study where temperature-dependent measurements of k₁(P, T) have been reported at pressures greater than 12 torr; hence, our results help constrain choices of k₁(P, T) for use in models of lower stratospheric BrO_x chemistry. Approximate falloff parameters in a convenient form for atmospheric modeling are derived. © 1993 John Wiley & Sons, Inc.