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

Abstract

The effect of deuteration on the quenching cross section (σQ2) has been determined for propane, cyclopropane, isobutane, and propylene. The results were as follows, with the σQ2 values, in Å2, 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 σQ2, indicating that C—H bonds are not involved in quenching. Further implications of the results with respect to the quenching process are discussed.