Local structure and tunneling kinetics of ammonium aluminum alum by infrared hole-burning.
The title compound, crystallized with a few percent of deuterium, contains some NH(3)D(+) and HOD. At low temperatures, five N-D stretch bands are observed. These belong to two ammonium sites with apparent C(s) symmetry in the low-temperature phase. The N-D bands can be hole-burned with an infrared laser. Burning bands belonging to the A-sites transforms some of them to the higher-energy B-sites. The A- and B-sites probably differ from each other by the arrangement of water and sulfate about the ammonium.
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Department of Chemistry, University of California, Berkeley 94720-1460, USA.
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