Knowledge Bank

Emission spectra of spin excited iodine in a crystalline Xe at 15 K, 35 K and 110 K are presented and analyzed in terms of anisotropic pair interactions. In the octahedral rapping site, the atomic $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}P$ iodine states split into $E1/2$ and $G3/2$ states of the $Oh$ double group. The fourfold degenerate $G3/2$ state is subject to a strong Jahn-Teller instability and further splits by coupling to phonons into $E1/2$ and $E3/2$ Kramers pairs. The observed emission spectra are composed of two bands corresponding to $2E1/2\to 1E1/2$ and $2E1/2\to 1E3/2$ transitions. The isolated atom spectra are simulated by Monte Carlo methods which assume classical statistics in the heavy atom coordinates, and adiabatic following of the electronic coordinate. Minor modifications of the gas phase pair interactions, and a temperature dependent spin-orbit splitting constant adequately reproduce the experimental spectra.