Direct measurement of exchange as a function of separation for discrete donor-acceptor pairs in ZnSe

We describe optical detection of magnetic resonance for 17 well-resolved discrete zinc interstitial donor-zinc vacancy acceptor pairs of varying separation in ZnSe. For most of the pairs, microwave transitions are detected between the exchange split triplet and singlet manifolds giving a direct high-precision measurement of the separated electron and hole exchange interaction in the excited emitting state of each pair. From these studies the E(+/2+) second donor state of the isolated interstitial zinc atom is estimated to be ∼$E_c$-0.8 eV.