The microwave spectrum and molecular structure of N2–HCl

Abstract

The structure of the van der Waals molecule N2–HCl has been determined by molecular beam electric resonance spectroscopy. The microwave spectrum is well fitted by a linear hydrogen-bonded structure with the following spectroscopic constants: Constant 14N2–H 35Cl 15,14N2–H35Cl 14,15N2–H35Cl In addition, spectra for the two chlorine isotopes of the complex formed using 15N2 are presented and analyzed. Electric quadrupole coupling hyperfine structure of 14N and 35,37Cl, is used to determine the vibrationally averaged orientation of the submolecules. The HCl submolecule makes an average angle of 26° with the a axis of the complex in all isotopes studied, while the average angle for the N2 submolecule is estimated to be 19°. The hydrogen–bond length is 2.42 Å in the linear configuration which is virtually identical to the hydrogen-bond length in OC–HCl. It is shown that the electric dipole moments of a series of N2 and CO complexes are not simply related to the polarizabilities of N2 and CO. Analysis of the induced difference in the quadrupole coupling constants of the two nitrogen nuclei indicates a transfer of 0.036 of an electron from the outer to the inner nitrogen which will affect the observed dipole moment.