Chemi-ionization of excited mercury

Summary form only given, as follows. We report calculations of the chemi-ionization for the collisions of Mercury (Hg) atoms in the excited singlet and triplet P states (/sup 1,3/P), examining both the Penning and associative ionization mechanisms. The doubly-excited mercury dimer presents an intricate situation for chemi-ionization. For example, with only one of the atoms excited, chemi-ionization is not energetically possible. Some of the asymptotes correlating to two excited /sup 3/P atoms still lie just below the energy of the atomic ion so that only associative ionization can occur. On the other hand, others lie just above it, enabling both associative and Penning ionization. Potential energy curves for the excited neutral (Hg/sub 2/**) and the ion (Hg/sub 2//sup +/) molecular states are generated using relativistic effective core potentials and full four-electron configuration interaction, based upon the orbitals of the ground state at each internuclear distance. We have examined the influence of core-valence correlation and the errors associated with the interaction curves will be discussed. For such heavy atomic systems, the spin-orbit interaction plays an important role, and its inclusion follows from an effective hamiltonian based on the atomic splittings. Finally, we shall present the cross sections for Penning and associative ionization.