Vacuum-Ultraviolet Photolysis of Ethane at High Temperature

The rates of production of HD in the photolysis of C₂H₆+C₂D₆ at 1470 and 1236 Å at temperatures sufficiently high to eliminate internal scavenging have been used as a measure of the relative importance of molecular elimination and atomic elimination processes. This, together with complete product analysis including isotopic determinations, gives the following relative weights for the primary processes $$\begin{array}{ccc}& \text{1470 Å}& \text{1236 Å}\\ {\mathrm{C}}_2{\mathrm{H}}_6^{*}\to {\mathrm{H}}_2+{\mathrm{C}}_2{\mathrm{H}}_4^{†}& \text{1.00}& \text{1.00}\\ {\mathrm{C}}_2{\mathrm{H}}_6^{*}\text{→2}\mathrm{H}+{\mathrm{C}}_2{\mathrm{H}}_4& \text{0.15}& \text{0.88}\\ {\mathrm{C}}_2{\mathrm{H}}_6^{*}\to {\mathrm{CH}}_4+{\mathrm{CH}}_2& \text{0.02}& \text{0.50.}\end{array}$$ The probability of dissociation of C₂H₄^† into H₂ and C₂H₂ increases relative to collisional stabilization by a factor of about 2 when the energy of the exciting photon is increased from 1470 to 1236 Å.