The rotational spectrum and structure of van der Waals complexes

Abstract

The microwave and radiofrequency stark spectra of the weakly bound neon-deuterium chloride complexes (Ne · D ³⁵Cl and Ne · D ³⁷Cl) have been obtained by the molecular beam electric resonance technique. Only transitions within the ground vibrational state have been observed. The analysis of the spectra has provided accurate values of the rotational constants, centrifugal distortion constants, nuclear quadrupole coupling constants and the electric dipole moment of each isotopic species. The spectroscopic data are consistent with the linear geometry found in similar rare gas-hydrogen halide complexes and with the atomic arrangement NeDCl. The complex is shown to be extremely non-rigid with the motion of the DCl sub-unit best described as a hindered rotation. In addition the complex Ne · HCl is confirmed to appear non-polar. The effective structure of Ne · DCl is determined to be R(Ne-Cl) = 3·84 Å, (∠ NeClD)_av ⋍ 65°. Finally a qualitative comparison is made with the structures of related rare gas-hydrogen halide complexes.