Stark effect of the F centre in CaO

Measurements have been made on the effect of an applied electric field on the 5742 AA zero-phonon emission line of the F centre in CaO. Results are interpreted taking account of both electronic polarization (Stark effect) and of ionic effects (electrostriction). It is shown that the latter are essential for the understanding of the overall effect. The measurements allow a determination of the position of 3S relative to 3P. E(3S)-E(3P) approximately=1200 cm-1 to 1500 cm-1. On the basis of this result the theory of the electric field effect on the zero-phonon line of the absorption of the F+ centre in CaO is re-examined.