Excited states of the H3 vibronic centre in diamond

Absorption and luminescence-excitation measurements show that the H3 vibronic centre in diamond (zero-phonon line at 2.463 eV) has a series of excited states which give rise to absorption lines between 3.2 and 3.6 eV. There is no luminescence produced by transitions from these higher excited states to the ground state. Following absorption in this region the centre relaxes to the lowest excited state and then emits luminescence in the vibronic band associated with the 2.463 eV line.