We describe timehyphen;resolved and spectrally resolved laserhyphen;induced fluorescence measurements from the parity or Lgr; doublet levels of theAthinsp;1Pgr; state of BCl radicals formed by CO2laser multiphoton dissociation of BCl3molecules. We show how the effects of collisional mixing can be discerned from the effects of electric field mixing. A set of rate equations for population transfer which include the effects of both field and collisional mixing under conditions of incoherent excitation are derived and compared to the more general theory of Alexander. Zerohyphen;field measurements of collisional mixing rates yield parityhyphen;changing rate constantskefwhose rotational quantum numberJdependence is consistent with a dipolendash;inducedhyphen;dipole collision model:kef=3.4,thinsp;2.6,thinsp;1.9, and 1.4times;106sminus;1thinsp;Torrminus;1forJ=3,thinsp;5,thinsp;11, and 18, respectively. Measurement of timehyphen;resolved fluorescence from Stark mixed parity levels in the presence of a strong electric field indicates that the levels are prepared coherently. Time integrated measurements as a function of the applied field are used in generating empirical calibration curves for determining local field magnitudes in discharges containing BCl radicals.
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