Studies of Chemiluminescence.

Abstract

Chemiluminescence has been observed from the reaction of the Group V hydrides (arsine, phosphine, and stibine) with ozone and oxygen atoms. Low resolution spectra are reported which reveal discrete b and emission attributed to the respective monoxide and visible continua. The quantum yields of the hydride reactions with O(,3)/O(,2) were found to be in the range 10('-3)-10('-4) photons per hydride molecule input. With O/O(,2) reagent, the quantum yields were found to be significantly higher with that for phosphine near unity under some conditions. A prototype hydrides analyzer based on chemiluminescence with ozone has been developed capable of detecting these species at mixing ratios as low as 0.6 ppbv for arsine, 0.4 ppbv for stibine, and 9 ppbv for phosphine. Using this detector, the decay of arsine (< 100 ppbv) in oxygen, air, and moist air was found to be negligible over a period of several days. Arsine was found to decay in excess ozone with a measured rate constant of (5 (+OR-) 2) x 10('-18) cm('3) molecule('-1) sec('-1). A continuous arsenic atom generation system was developed and preliminary kinetic studies were performed using a discharge-flow system. The reaction As + O(,2) was found to be bimolecular, producing chemiluminescence. This emission was found to be indistinguishable from the visible continuum observed in the AsH(,3) + O(,3), O/O(,2) chemiluminescent emissions. The light emitter and reaction product is suggested to be OAsO. The rate constant was found to be (9 (+OR-) 3) x 10('-14) cm('3) molecule('-1) sec('-1) by both As resonance fluorescence and chemiluminescence. Third order kinetics and visible chemiluminescence were observed from the reaction As + NO. The reactions As + NO(,2), O(,3) were fast enough to be useful as As titration systems. The rate constants were estimated to be (GREATERTHEQ) 1.3 x 10('-11) and (GREATERTHEQ) 9 x 10('-12) cm('3) molecule('-1) sec('-1), respectively. Ultraviolet emission was observed with ozone and attributed to the reaction As + O(,3) (--->) AsO + O(,2) which is sufficiently exothermic to excite AsO to the A('2)(SIGMA) state.