OPTICAL AND EPR INVESTIGATIONS OF A NEW HYDROGEN CENTER IN POTASSIUM-CHLORIDE

In KCl interstitially diffusing neutral hydrogen atoms (Hi0) can be trapped near substitutional Li+ ions. The new center possesses a characteristic absorption band at 250nm, at the long wavelength side of the known Hi0 absorption band (235nm). EPR measurements reveal, that the hydrogen atoms are closely connected to the Li+ ions at a cation lattice site forming (LiH)+ molecules. Below 70K hydrogen and lithium occupy a fixed relative position to each other in a (111) crystal direction: the hydrogen shows a superhyperfine interaction to three equivalent Cl- neighboring ions. Above 70K the hydrogen exhibits a superhyperfine interaction to six equivalent chlorine neighbors, interpreted by a rapid reorientational motion of the (LiH)+ molecule within the cation vacancy. The high temperature interaction parameters can be explained as the time average of the low temperature values. A qualitative explanation of the optical absorption of the (LiH)+ center is given. © 1979 Springer-Verlag.