Energy Transfer in Monochromatically-Excited Hydrogen (B 1Σ u+). I. Excitation Processes, Electronic Quenching, and Vibrational Energy Transfer

Abstract

Excitation of HD molecules into specific vibrational and rotational levels of the ${\mathrm{B\hspace{0.17em}}}^1{\Sigma }_u^{+}$ electronic state by absorption of the 1048 and 1066 Å argon resonance lines has been studied under various experimental conditions by observing the steady‐state fluorescence spectra of the ${\mathrm{(B\hspace{0.17em}}}^1{\Sigma }_u^{+}{\mathrm{\to \; X\hspace{0.17em}}}^1{\Sigma }_g^{+})$ Lyman bands. Strong excitation of the $\text{(v′ = 3, J′= 2), (v′ = 5 , J′=2)}$ , and $\text{(v′ = 6 , J′ = 5)}$ levels was achieved. The HD ${\mathrm{(B\hspace{0.17em}}}^1{\Sigma }_u^{+}{\mathrm{\to \; X\hspace{0.17em}}}^1{\Sigma }_g^{+})$ electronic fluorescence from $\text{v′=3}$ was found to be quenched by HD, ³He, ⁴He, and Ne with effective collision cross sections of 79, 8.8, 9.9, and 3.5 Ų at 297°K. Vibrational energy transfer processes $$\mathrm{HD}{\mathrm{(B\hspace{0.17em}}}^1{\Sigma }_u^{+}\text{; v′=3, J′) +}\mathrm{M}\to \mathrm{HD}{\mathrm{(B\hspace{0.17em}}}^1{\Sigma }_u^{+}\text{; v′=2, J′ + Δ J′ ) +}\mathrm{M}\mathrm{+\; \Delta }\mathrm{E}$$ were studied for the collision partners ³He, ⁴He, and Ne. Large effective cross sections of 0.89, 0.76, and 0.81 Ų were found at 303°K. Rotationally‐resolved spectra for Ne show that vibrational energy is transferred into both rotation and translation. All energetically accessible values of ΔJ′ were observed. On the average one‐half of the vibrational energy was transferred into rotation.