SUBMILLIMETER SPECTROSCOPY OF ZnO (X$^{1}\Sigma^{+})$

Author Institution: Department of Chemistry, Department of Astronomy, and Steward Observatory, University of Arizona, Tucson, AZ, 85721The pure rotational spectrum of ZnO (X$^{1}\Sigma^{+})$ has been measured using millimeter-wave direct-absorption techniques. ZnO was produced by the reaction of zinc vapor and N$_2$O under d.c. discharge conditions. Over the frequency range 239-514 GHz, rotational transitions were measured for the ground and several vibrationally excited states of the five stable zinc isotopologues of ZnO. The $^{1}\Sigma^{+}$ ground state was confirmed, and the spectroscopic constants and equilibrium parameters were calculated. The bond length of zinc oxide was determined to be 1.708 \AA