PRESSURE-DEPENDENCE OF THE CN(B(2)SIGMA+-X(2)SIGMA+) EMISSION-SPECTRA IN AN AR FLOWING AFTERGLOW

The CN(B2SIGMA+-X2SIGMA+) emission spectrum produced in the reaction of Ar(3P2) with BrCN was observed by the use of a flowing afterglow method at argon pressures ranging from 9 mTorr to 2 Torr (1 Torr = 133.322 Pa). The pressure dependences of the intensity anomalies in the rotational lines due to the B2SIGMA+ approximately A2PI(i) and the B2SIGMA+ approximately 4SIGMA+ perturbations were measured by introducing collision-partner gases in the reaction region. These pressure dependences can be explained by the ''doorway'' model. On the other hand, the measured pressure dependence of the effective rotational temperature in the CN(B2SIGMA+) state can also be reproduced by the collision-induced rotational relaxation model. The cross section for the rotational relaxation in the A2PI(i) state was found to be smaller than those in the B2SIGMA+ and 4SIGMA+ states. This finding is interpreted by the use of the dipole-induced dipole interaction model for the collision-induced rotational relaxation.