Time-resolved molecular chemiluminescence investigations of SrO following pulsed dye-laser generation of Sr(5s5p( 3P J)) in the presence of N 2O

Abstract

Molecular chemiluminescence from SrO is studied in the time domain following pulsed dye-laser generation of Sr(5 3P J ) in the presence of N 2O at elevated temperatures (675–1100 K). Time-resolved atomic fluorescence at λ=689.3 nm and SrO chemiluminescence were optically isolated with a small monochromator and recorded photoelectrically using boxcar integration. The atomic decay profiles were employed to characterize the Arrhenius parameters for overall quenching between Sr(5 3P J ) + N 2O described by the overall rate constant k= (4.2 ± 1.9) × 10 −10 exp (−25.8 ± 5.7 kJ mol −1/ RT) cm 3 molecule −1 s −1. Time profiles for SrO chemiluminescence were characterized under conditions identical in each case to those employed to record the atomic profiles. Quantitative comparison of the time dependences of the atomic and molecular emission profiles showed that the SrO “orange” and “red” arc band emitting states result from direct reaction between Sr (5 3P J ) + N 2O giving rise to simple exponenti decay of chemiluminescence. By contrast SrO(A′ 1Π) and SrO(A 1Σ +) result from energy transfer between Sr(5 3P J ) and SrO (X 1Σ + and display a bi-exponential time dependence. Estimates of vibrational temperatures within SrO (A′ 1Π) show some measure of vibrational excitation above the Boltzmann temperature for ambient conditions, and the temperature variation of the SrO chemiluminescence intensity overall is shown to be consistent with thermodynamic data for atomic strontium.