Assignment of Invisible Combination Bands in Ammonium Zinc Tutton Salt by Infrared Hole Burning

A polycrystalline sample of the title compound containing a small fraction of deuterium was irradiated in an infrared region containing no apparent absorption bands. Holes and antiholes were produced in the N−D stretching bands. Each irradiation thus was at the wavenumber of a combination band involving a particular N−D stretch. Most of the combinations consist of the N−D stretch of the ammonium ion together with an internal mode of the zinc complex ion.