Nuclear Quadrupole Resonances in Arsenic Tribromide and Arsenic Tri-iodide

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.