EMILY D. TENENBAUM, MICHAEL A. FLORY, ROBIN L. PULLIAM AND LUCY M. ZIURYS, Steward Observatory, University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721.
The radical ZnCl has been studied with high-resolution millimeter-wave spectroscopy in its 2 + ground state. Pure rotational spectra of 64Zn35Cl, 64Zn37Cl, and 66Zn35Cl were measured in the ground and excited vibrational states (v=1,2), and measurements of 67Zn35Cl, 66Zn37Cl, and 68Zn35Cl were recorded in the ground state. Each rotational transition was found to be split into doublets by spin-rotation interactions, and for 67Zn35Cl, hyperfine splittings due to the nuclear spin of 67Zn (I=5/2) were also observed. Rotational, fine structure, and hyperfine constants have been determined from these data, and equilibrium parameters calculated. The equilibrium bond length of 64Zn35Cl was found to be 2.13003(57)Å, in good agreement with recent theoretical predictions. Interpretation of the hyperfine constants indicates that the ZnCl bond is mostly ionic.