Nuclear Quadrupole Resonances in Arsenic Tribromide and Arsenic Tri-iodide

Abstract

The pure quadrupole spectra of As ⁷⁵ , Br ⁷⁹ and Br ⁸¹ in AsBr ₃ , and of I ¹²⁷ in AsI ₃ have been studied by the method of superregenerative detection. The observed resonance frequencies yielded the following couplings: 127 Mc, 415 Mc and 1328 Mc for As ⁷⁵ , Br ⁷⁹ and I ¹²⁷ respectively. The spectrum of bromine in arsenic tribromide was a triplet. Above 90°C, the iodine in arsenic tri-iodide also showed a triplet, whereas below that temperature it had a single line. The asymmetry parameter on iodine was determined from the resonance frequencies. The result was 18.4% at the liquid air temperature and 14.5% at the room temperature. The low couplings and the high asymmetry of iodine in arsenic tri-iodide were interpreted by the mechanism of resonance switching of the bond.