THE QUENCHING OF MERCURY RESONANCE RADIATION BY HYDROCARBONS: THE EFFECT OF DEUTERIUM SUBSTITUTION

Abstract

The effect of deuteration on the quenching cross section (σ_Q²) has been determined for propane, cyclopropane, isobutane, and propylene. The results were as follows, with the σ_Q² values, in Ų, in parentheses: C₃H₈ (1.2); CH₃CD₂CH₃ (0.17); CD₃CH₂CD₃ (1.0); C₃D₈ (0.09); cyclo-C₃D₆ (0.29); (CH₃)₃CH (4.8); (CH₃)₃CD (0.44); C₃H₆ (29.8); and C₃D₆ (28.7). The deuterium isotope effect is most pronounced in the secondary C—H bonds of propane, and the tertiary C—H bond of isobutane. In the latter case, the isotope effect is estimated to be 15–16. For propylene, perdeuteration has little, if any, effect on σ_Q², indicating that C—H bonds are not involved in quenching. Further implications of the results with respect to the quenching process are discussed.