131Xe nuclear quadrupole coupling and the rotational spectra of XeHCl

Rotational spectra have been assigned for the 129XeH35Cl, 129XeH37Cl, 129XeD35Cl, 131XeH35Cl and 132XeH35Cl van der Waals molecules by employing pulsed microwave Fourier transform spectroscopy in a Fabry–Perot cavity with a pulsed supersonic nozzle as the molecular source. The rotational constants, centrifugal distortion constants, and Cl nuclear quadrupole coupling constants obtained from the spectra are used to determine the structure of XeHCl and to gain information on the intermolecular potential binding of Xe to HCl. From the spectrum of 131XeH35Cl and an analysis of the centrifugal distortion in 129XeH35Cl, 131XeH35Cl, and 132XeH35Cl the 131Xe nuclear quadrupole coupling constant in XeHCl is found to be −4.9±0.2 MHz. Using the known nuclear quadrupole moment of 131Xe, the electric field gradient at the Xe nucleus is calculated. The observed field gradient is discussed in terms of Sternheimer shielding and formation of the weak Xe–HCl van der Waals bond.