Exciton-absorption edge and Urbach rule in LiH and LiD single crystals O'Konnel-Bronin, A. A. ; Plekhanov, V. G. ; Pustovarov, V. A. ; Gavrilov, F. F. ; Cholakh, S. O. Abstract Publication: Optics and Spectroscopy Pub Date: August 1981 Bibcode: 1981OptSp..51..204O