Measurement of molecular magnetic susceptibility anisotropies

Abstract

The rotational energy levels of a rigid spin-free molecule in the presence of a high magnetic field are determined. Terms up to H⁴ dependence are included and all rotational-electronic corrections included through second order in the electronic states. The results show that in the absence of near rotational degeneracies, the field-dependent perturbation is well described by the three diagonal g-values (g_aa, g_bb and g_cc) and two independent magnetic susceptibility anisotropy components ((2X_aa–X_bb–X_cc) and (2X_bb–X_aa–X_cc)). These five molecular Zeeman parameters can be extracted from the analysis of pure rotational spectra in high magnetic fields. The magnetic susceptibility are anisotropies for about 40 molecules have been determined recently by these techniques and the results are listed here. Ring currents and group anisotropies are also discussed.