Electron spin-echo envelope modulation in randomly oriented doublet and triplet systems

Abstract

Numerical calculations are presented of the distribution of electron spin-echo envelope modulation frequencies of randomly oriented S = 1 2 , I = 1 2 and S = 1, I = 1 2 systems with one axial hyperfine tensor. It is shown that for both systems the hyperfine coupling constant obtained from the maximum of the distribution of electron spin-echo envelope modulation frequencies will be close to the isotropic hyperfine coupling constant only if the nuclear Zeeman frequency is much larger than the hyperfine interaction or vice versa. When the nuclear Zeeman field is almost canceled by the hyperfine field the nuclear transition frequency approaches zero and, depending on the values of the isotropic and anisotropic hyperfine interaction, the resultant hyperfine coupling constant may yield any value between the parallel and perpendicular component of the axial hyperfine tensor.