Knowledge Bank

We have observed weak-field hyperfine transitions in KC1 for vibrational-rotational states (v,J) = (0, 2-9)and (1, 2-4) using a high resolution molecular beam spectrometer. Linewidths of the observed transitions are 200 Hz (FWHM). Analysis of the (v,J) = (0,2) data yields the following set of hyperfine interaction constants for the $\mathrm{<mrow\; data-mjx-texclass="ORD">39</mrow>}K35Cl$ isotope (in units of kHz): [FIGURE} \begin{eqnarray*} (eqQ){K} &=& - 5664.74 (5)\ (eqQ){Cl} &=& 56.2 (5)\ ^{c}K &=& 0.035 (10)\ ^{c}Cl &=& 0.46 (1)\ d_{T} &=& 0.07 (2)\ d_{S} &=& 0.01 (2)\ \end{eqnarray*} The quadrupole constants lie outside the experimental uncertainties of previously-reported measurements made at lower resolution and high field on the J = 1 $state.1$ Analysis of the higher rotational and vibrational states is in progress. $^{1}$1 R. van Wachem and A. Dymanus, J. Chem. Phys. 46, 3749 ( 1967). This work is supported in part by a Northwest Area Foundation Grant of Research Corporation.