Quenching rate constants of metastable states of neon, argon, and krypton by mercury atoms

Abstract

Room temperature rate constants (thermal average cross sections) for the quenching of electronically excited state rare gas metastable atoms by mercury atoms have been measured using the flowing afterglow technique. The thermal cross sections are σQ[Ne(3P2)]=70 Å2;σQ[Ar(3P2)]=194 Å; σQ[Ar(3P0)]=219 Å2; and σQ[Kr(3P2)] =124 Å2. The mechanism for quenching by mercury atoms is Penning ionization for Ne* and Ar*, and excitation transfer for Kr*. These results are discussed in terms of the cross section of similar reagents and the cross section predictions of the close collision criteria. The large experimental cross sections indicate that the total quenching cross section is dictated by interactions occuring at large internuclear distances associated with a long range attractive potential. However, the interactions at shorter range are responsible for the actual conversion from reactants to products. The Kr(3P2) +Hg excitation transfer reaction provides a way to generate Hg(3P2) metastable atoms in a flowing afterglow apparatus.