Exact expression for the spin 7/2 line intensities: Application to solid state ⁵⁹Co(III) NMR

Abstract

The density matrix of a spin I = 7/2, excited by a radiofrequency pulse, is calculated in taking into account the first order quadrupolar interaction during the excitation. Therefore, the results are valid for any ratio of the quadrupolar coupling ω_Q to the pulse amplitude ω_RF. The behaviour of the central line intensity versus the pulse length is discussed both in time and frequency domains. The quadrupolar coupling constant e ² qQ/h = 8·24 MHz of the ⁵⁹Co(III) nucleus in a polycrystalline sample of Na₃[Co(NO₂)₆] is determined using this one-dimensional nutation method, and the lineshape reveals mainly the presence of chemical shift anisotropy with axial symmetry.