The sub-millimeter and Fourier transform microwave spectrum of HZnCl (X 1Σ +)

Abstract

The pure rotational spectrum of HZnCl (X 1Σ +) has been recorded using sub-millimeter direct-absorption methods in the range of 439–540 GHz and Fourier transform microwave (FTMW) techniques from 9 to 39 GHz. This species was produced by the reaction of zinc vapor and chlorine gas with H 2 or D 2 in a d.c. glow discharge for the sub-millimeter studies. In the FTMW measurements, HZnCl was created in a discharge nozzle from Cl 2 and (CH 3) 2Zn. Between 5 and 10 rotational transitions were measured in the sub-millimeter regime for four zinc and two chlorine isotopologues; four transitions were recorded with the FTMW machine for the main isotopologue, each consisting of several chlorine hyperfine components. The data are consistent with a linear molecule and a 1Σ + ground electronic state. Rotational and chlorine quadrupole constants were established from the spectra, as well as an r m (2) structure. The Zn–Cl and Zn–H bond lengths were determined to be 2.0829 and 1.5050 Å, respectively; in contrast, the Zn–Cl bond distance in ZnCl is 2.1300 Å, longer by ∼0.050 Å. The zinc–chlorine bond distance therefore shortens with the addition of the H atom. The 35Cl electric quadrupole coupling constant of eQq = −27.429 MHz found for HZnCl suggests that this molecule is primarily an ionic species with some covalent character for the Zn–Cl bond.