Molecular Zeeman Effect and the Determination of the Molecular Magnetic Moments (g Values), Magnetic Susceptibilities, and Molecular Quadrupole Moments in Methyl Formate and Glycolaldehyde

Abstract

The high-field first- and second-order Zeeman effect has been observed in methyl formate and glycolaldehyde. The molecular parameters in the inertial axis system for both molecules are listed below. Only the relative signs of the molecular g values are obtained experimentally. However, the absolute signs are conclusively assigned in both molecules by an analysis of the second moment of the charge distribution or molecular quadrupole moments. For methyl formate, the measured g values and magnetic susceptibility anisotropies are gaa = − 0.1267 ± 0.0013, gbb = − 0.0391 ± 0.0010, gcc = − 0.0168 ± 0.0017, 2χaa − χbb − χcc = (11.0 ± 1.0) × 10−6erg/G2·mol, and 2χbb − χcc − χaa = (3.1 ± 1.0) × 10−6erg/G2·mol. The molecular quadrupole moments are Qaa = (2.3 ± 0.8), Qbb = (4.2 ± 1.0), and Qcc = − (6.5 ± 1.3) all in units of 10−26 esu·cm2. For glycolaldehyde, the measured g values and magnetic susceptibility anisotropies are gaa = − 0.1239 ± 0.0013, gbb = − 0.0726 ± 0.0010, gcc = − 0.0178 ± 0.0010, 2χaa − χbb − χcc = (7.1 ± 2.5) × 10−6erg/G2·mol, and 2χbb − χcc − χaa = (18.8 ± 2.0) × 10−6erg/G2·mol. The molecular quadrupole moments are Qaa = − (5.6 ± 2.0), Qbb = (3.8 ± 1.8) and Qcc = (1.8 ± 3.3) in units of 10−26 esu·cm2. Using the molecular structures allows a determination of the diagonal elements in the paramagnetic susceptibility tensor and the anisotropies in the second moment of the charge distribution. Using the bulk susceptibilities, gives the diagonal elements in the total magnetic susceptibility tensor and the individual elements of the second moment of the charge distribution. The results in these two molecules are compared to similar systems.