Abstract
The uniaxial stress splitting of an optical transition observed in photoluminescence depends on the way the population of excited states was achieved. For transitions at monoclinic centres induced by an electric dipole perpendicular to the main axis of the centre, that splitting pattern is also dependent on the precise orientation of the dipole. This communication reports on the splitting under uniaxial stress of an electric-dipole transition occurring at monoclinic II centres, observed in absorption and photoluminescence. The results are used to interpret the behaviour under uniaxial compression of the 2.424 eV transition in diamond.