Motions of Molecules in Condensed Systems. IV. The Infra-Red Spectra for Ammonium Nitrate and Thallous Nitrate

Abstract

The infra‐red absorption spectra from 680 to 3600 cm−1 have been recorded for five crystalline modifications of NH4NO3 at 150°, 105°, 55°, 25°, and −40°; also the spectra from 680 to 1450 cm−1 of three modifications of TlNO3 at 170°, 100°, and 25°. Fundamental frequencies of the nitrate ion were found for NH4NO3 at 715, 830, 1050, and 1350 cm−1 (those for TlNO3 were found at approximately the same positions) and of the ammonium ion at 1430, 1760, 3100, 3200 cm−1. The spectrum of each compound remains essentially the same with change of temperature, except that in NH4NO3 at 150° and 105° the band at 715 cm−1 is absent. It is notable that bands at 1050, 1760, and 3100 cm−1, supposedly caused by symmetric vibrations, remain active in all crystal forms investigated.