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

Abstract

The 115In NQR spectra in layered InSe single crystals for four spin transitions, the average values of which only approximately satisfied the ratio v1:v2:v3:v4 =1:2:3:4 were studied. It was found that for higher transitions a deviation is observed. In particular, it is shown that additional lines are observed in the multiplet groups for higher-order transitions, which, in our opinion, is associated with the presence of a hexadecapole interaction with the gradient of the crystal electric field.