Time-resolved emission studies of the collisional quenching of Ca(43PJ) and Sr(53PJ) by various gases in an equilibrium-coupled system following pulsed dye-laser excitation at λ= 657.3 nm [Ca(43P1)â†� Ca(41S0)

Abstract

The collisional quenching of Ca(4 3PJ) and Sr(5 3PJ) has been studied for an equilibrium system coupled by the process Ca(4 3PJ)+ Sr(5 1S0)⇌ Ca(4 1S0)+ Sr(5 3PJ) and established following pulsed dye-laser excitation of Ca(4 1S0) to Ca(4 3P1) at λ= 657.3 nm in mixtures of calcium and strontium vapour in the presence of an excess of helium buffer gas and added quenching gases. Ca(4 3P1), Sr(5 3P1) and Sr(6 3S1) were monitored by time-resolved emission at λ= 657.3, 689.3 [Sr(5 3P1)→ Sr(5 1S0)+hν) and 679.1 nm [Sr(6 3S1)→ Sr(5 3P0)+hν], respectively, using boxcar integration. The measured first-order decay coefficients for Ca(4 3PJ) and Sr(5 3PJ) under equilibrium-coupled conditions were found to be in quantitative agreement with previously measured values of absolute second-order rate constants for the quenching gases Kr, Xe, H2, D2, N2, CO, NO, N2O, CO2, NH3, CH4, CF4, C2H2, C2H4 and C6H6, obtained using the present system, employing signal averaging, on decays of Ca(4 3PJ) and Sr(5 3PJ) individually. Finally, energy pooling according to the processes Ca(4 3PJ)+ Sr(5 3PJ)→ Sr(6 3S1)+ Ca(4 1S0), Sr(5 3PJ)Sr(5 3PJ)→ Sr(6 3S1)+ Sr(5 1S0) was investigated quantitatively from measurements at λ= 679.1 nm in the time domain and in the presence of the quenching gases.