Knowledge Bank

The pure rotational spectra of ZnO in the excited a$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Pi i$ electronic state have been measured using direct absorption sub-millimeter techniques. This molecule was synthesized by reacting zinc vapor with N$2$O in the presence of a DC discharge. Nine rotational transitions were recorded for the $\mathrm{<mrow\; data-mjx-texclass="ORD">64</mrow>}$ZnO, $\mathrm{<mrow\; data-mjx-texclass="ORD">66</mrow>}$ZnO, and $\mathrm{<mrow\; data-mjx-texclass="ORD">68</mrow>}$ZnO isotopomers in the v=0 state and data for the main isotopomer was measured in the v=1 state. All three spin components were observed for this state, each exhibiting lambda-doubling. The data were fit with a Hund case(a) Hamiltonian and rotational, spin-orbit, spin-spin, and lambda-doubling constants established. A bond length of 1.8436 \AA{} was determined for this excited state, which is about 0.14 \AA{} larger than that of the ground state.