Optical and EPR investigations of a new hydrogen center in potassium chloride |
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Authors: | L O Schwan W Geigle H Paus |
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Institution: | (1) Physikalisches Institut (Teil 2) der Universität, Pfaffenwaldring 57, D-7000 Stuttgart-80, Federal Republic of Germany |
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Abstract: | In KCl interstitially diffusing neutral hydrogen atoms (H
i
0
) can be trapped near substitutional Li+ ions. The new center possesses a characteristic absorption band at 250nm, at the long wavelength side of the knownH
i
0
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. |
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