$^{87}Rb$ NMR Quadrupole Coupling Constants and Asymmetry Parameters in $RbMnCl_3$

The 87Rb quadrupole coupling constants (e2qQ/h) and the asymmetry parameters (η) in RbMnCl3 were determined from a nonlinear least-squares fit to the 87Rb NMR powder spectra. The spectra were acquired in the temperature range from 260K to 330K. An important feature in this work is the determination of the quadrupole coupling constants and the asymmetry parameters for two physically nonequivalent Rb sites, Rb(I) and Rb(II), as a function of temperature. In addition, a structural phase transition at room temperature was conformed with the changes in the quadrupole coupling constant and the asymmetry parameter of Rb(II) site.