The trigonal Cr2+(II) centre in GaAs: refinements in the5E excited state

A revised analysis the high-resolution photoluminescence zero-phonon line at 0.839 eV in chromium-doped GaAs crystals is described. The excited 5 E states are fitted to the Hamiltonian H= Lambda T 3 S z +D 0 S Z 2 for the trigonal Cr 2+ (II) centre with Lambda =-1.51 meV and D 0 =-0.075 meV. It is shown that the above splittings within the 5 E excited states are much larger than those within the 5 T 2 ground states because spin-orbit coupling admixes the nearby 3 T 1 and 3 T 2 states into 5 E.