BAND STRUCTURE AND THEORY OF POLARONS AND F-CENTRES IN ALKALI-HALIDES

A method for the determination of the electron effective masses and of the position of the electron energy minima in K-space from the ENDOR data is proposed. The application of the method to F-centres in KCl and NaF shows that the electron wawe functions of the F-centre are made up from the states of the six-valley band with the energy minima at the axis (1, 0, 0). It is shown that the above results are not in contradiction with the available band structures in alkali halides and with the existing theory of the F-centre. The polaron theory is extended to the case of multivalley cubic crystals. © 1969 Società Italiana di Fisica.