Summary: Atomic oxygen in crystalline Kr and Xe. II. Adiabatic potential
A. V. Danilychev and V. A. Apkarian
Department of Chemistry, Universiv of California, Irvine, California 92717
(Received 8 October 1993; accepted 4 January 1994)
The potential energy surfaces of atomic oxygen, O(3P, `D, `S), trapped in crystalline Kr and Xe are
developed based on known angularly anisotropic pair interactions. The electrostatic limit, with the
neglect of exchange and spin-orbit interactions, is assumed. Using a classical statistical treatment
for the simulation of spectra, the surfaces are shown to reproduce the experimental O(`S+`D)
emissions in substitutional and interstitial sites of crystalline Kr. The surfaces are also in accord with
charge transfer emission spectra of O/Xc solids. With lattice relaxation, the Xe-0( `D)-Xe
insertion site becomes the global minimum, and can therefore act as a stable trap site. This is in
accord with experimental observations of a third trapping site in Xe. To rationalize the recently
reported long-range mobility of 0 atoms in these solids [A. V Danilychev and V A. Apkarian, J.
Chem. Phys. 99, 8617 (1993)], the topology of various electronic surfaces are presented. It is shown
that the minimum energy paths connecting interstices on the triplet and singlet surfaces are quite
different. The triplet path is strongly modulated and proceeds along body diagonals of the unit cell.
The singlet path is more gently modulated and proceeds along face diagonals. These features are
consistent with the postulated thermal mobility as proceeding via triplet-singlet conversion.
However, on a quantitative basis, the electrostatic surfaces fail to support the model. The site