Evaluation of the contribution of higher-order electron-nuclear interactions to the NQR frequencies using 115In spectra in InSe

Abstract

Using the continuous NQR method with synchronous detection in the sweep mode, in melt-grown layered InSe single crystals, the 115In NQR spectra were studied for four 115In resonance transitions with spin 9/2, the average values of which only approximately satisfied the ratio v1:v2:v3:v4 = 1: 2: 3: 4. It is established that for higher-order transitions there is a deviation of the frequency multiplicity. In particular, it is shown that additional lines are observed in multiplet groups for higher-order transitions, which, in our opinion, is due to the presence of hexadecapole interaction of 115In nuclei with the electric field gradient in InSe.