Non-Radiative De-Excitation of Highly Excited Self-Trapped Excitons in Alkali Halides: Mechanism of theFandHCentre Production

We calculate the rates of non-radiative transitions among the excited states of the self-trapped exciton in KCl. The transition matrix elements are calculated using the same semi-empirical molecular orbital method (CNDO) as in our earlier calculations of the energy surfaces and radiolysis mechanism. The results are consistent with current experiments. One important result is that the non-radiative decay of the lowest electron-excited state of the self-trapped exciton proceeds more rapidly to the lowest hole-excited state than to the ground triplet state. Transfer of excitation energy from the electron to the hole (and hence the production of F and H centres) can proceed rapidly.