Knowledge Bank

Although the vibration-rotation spectrum of $H3O+$ has been studied extensively, there has been no experimental information on the value of the C rotational constant because of the absensce of $\Delta |k-l|\ne 0$ forbidden transitions. There is a near degeneracy between the (9,0)$\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ and the (9,3)$\mathrm{<mrow\; data-mjx-texclass="ORD">-</mrow>}$ ground state rotation-inversion levels, as pointed out by Verhoeve, $etal.1$ Indeed the ground state combination differences of the $v3$ fundamental transitions show a sizable shift of the (9.3)$\mathrm{<mrow\; data-mjx-texclass="ORD">-</mrow>}$ level as well as the neighboring (7,3)$\mathrm{<mrow\; data-mjx-texclass="ORD">-</mrow>}$ and (11,3)$\mathrm{<mrow\; data-mjx-texclass="ORD">-</mrow>}$ levels. We have obtained 11 forbidden $v3$ transitions involving these ground state levels. This enabled us to determine the energy difference between different K levels and the mixing coefficient $\tau xxxz$. An extended analysis of the $v3$ bands is in progress.