High Resolution Study of the Rotational Spectrum of Formaldoxime, Combined with Quantum Chemical Calculations, Its ¹⁴N Spin-Rotation Coupling, ¹⁴N Nuclear Quadrupole hfs, and Its Rotational Zeeman-Effect

Abstract

Abstract A high resolution study of the rotational spectrum of formaldoxime was carried out with the aim to resolve a discrepancy between early microwave results and recent ab initio calculations. Accurate 14 N quadrupole coupling constants and spin-rotation coupling constants could be derived from zero field hfs multiplets. From the Zeeman-splittings in external magnetic fields up to 18kGauss the diagonal elements of the molecular g-tensor and the anisotropics in the diagonal elements of the molecular magnetic susceptibility tensor were obtained and were used to derive the diagonal elements of the molecular electric quadrupole moment tensor. For comparison, Hartree Fock SCF calculations were carried out with a basis of TZVP quality. As it turned out such calculations are able to reproduce the molecular electric quadrupole moment tensor but fail to reproduce the 14 N nuclear qudrupole coupling constants to better than 0.3 MHz. A revised formula to predict spinrotation coupling constants of first row elements such as nitrogen is also proposed.