Molecular ɡ-values, Magnetic Susceptibility Anisotropics, Molecular Electric Quadrupole Moments, improved Molecular Electric Dipole Moments and ¹⁴N-Quadrupole Coupling Constants of Acrylonitrile, H₂C = CH—CN, and the Magnetic Susceptibility Tensor of the Nitrile Group

Abstract

The highfield, linear and quadratic Zeeman effect has been observed in Acrylonitrile (Vinyl Cyanide). The Zeeman multiplets are complicated by the presence of the 14 N nuclear quadrupole coupling, however the 14 N nuclear Zeeman effect effectively uncouples 14 N spin from the rotational angular momentum. This uncoupling was used to derive improved molecular electric dipole moments from the Stark-shifts in the 2 11 ← 2 02 and 3 12 ← 3 03 rotational transitions observed under ΔM j =0 selection rule in the presence of a high magnetic field. They are |μ a | = 3.815(12)D and |μ b | = 0.894(68)D, respectively. From the zero field hfs multiplets, observed under high resolution conditions, improved 14 N quadrupole coupling constants were obtained: χ aa N = - 3.7800(21) MHZ, χ bb N - χ cc N = - 0.4200(89) MHz. They are discussed with reference to the structure of the Nitrile group. From the Zeeman splittings of the 1 01 ← 0 00 , 1 10 ← 1 01 , 2 11 ← 2 02 and 3 12 ← 3 03 rotational transitions observed under ΔM j = 0 and ΔM j = ± 1 selection rule, the diagonal elements of the molecular g-tensor and the anisotropics in the diagonal elements of the molecular magnetic susceptibility tensor were obtained as g aa = -0.17901(33), g bb , = - 0.04585(17), g cc = -0.01820(16) and 2 χ aa - χ bb - χ cc = - 7.22(25) 10 -6 erg G -2 mole -1 and 2χ bb - χ cc - χ aa = + 15.90(31) 10 -6 erg G -2 mole -1 . They are discussed with reference to the molecular electric quadrupole moment, the paramagnetic and diamagnetic contributions to the molecular susceptibilities, and the second moments of the electronic charge distribution. The susceptibility data are also used to derive the magnetic susceptibility tensor contribution of the Nitrile group.