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

The pure rotational spectrum of HZnCl (X R) 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 H2 or D2 in a d.c. glow discharge for the sub-millimeter studies. In the FTMW measurements, HZnCl was created in a discharge nozzle from Cl2 and (CH3)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 R ground electronic state. Rotational and chlorine quadrupole constants were established from the spectra, as well as an rm 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 Cl 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. 2009 Elsevier Inc. All rights reserved.