Hydrogen–Chlorine Explosion Laser. II. DCl

Abstract

Further work on the H₂–Cl₂ explosion laser shows that the emission occurs in $\text{υ\hspace{0.17em}=\hspace{0.17em}2\hspace{0.17em}→\hspace{0.17em}1}$ vibration–rotation transitions $P_2\text{(4)}\mathrm{to}{P}_2\text{(8)}$ instead of 1 → 0 transitions, as concluded earlier. The laser emission is intensified with higher flash energy and with shorter flash duration. The effects of reactant pressures reflect the factors that influence the rate of the first reaction in the explosion chain. Raising temperature raises the laser gain, again due to acceleration of the Cl + H₂ reaction, despite Doppler broadening, pressure broadening, and increased rotational dilution. With all conditions optimized, the D₂–Cl₂ explosion laser was successfully operated giving DCl 2 → 1 transitions $P_2\text{(7)}\mathrm{to}{P}_2\text{(9)}$ . With HD–Cl₂ mixtures, both HCl and DCl emissions were obtained. By mixing HD, H₂, and D₂ we were able to deduce for the first time the relative rates of the two reactions $$\mathrm{Cl\hspace{0.17em}+\hspace{0.17em}HD\hspace{0.17em}\to \hspace{0.17em}}{\displaystyle {lim}^{k_H}}\mathrm{HCl\hspace{0.17em}+\hspace{0.17em}D}$$ and $$\mathrm{Cl\hspace{0.17em}+\hspace{0.17em}HD\hspace{0.17em}\to \hspace{0.17em}}{{\displaystyle {lim}^k}}_D{\mathrm{DCl\hspace{0.17em}+\hspace{0.17em}H:\; k}}_H{\mathrm{\hspace{0.17em}/\hspace{0.17em}k}}_D\text{\hspace{0.17em}=\hspace{0.17em}1.9}$$ . The important processes in this chemical laser are becoming clear. A crucial datum needed for the determination of energy distribution among the vibrational levels is the rotational temperature at the time laser threshold is reached, since $T_r$ rises during the explosion.