Knowledge Bank

Laser excitation spectroscopy has been used to record the (0-0) bands of the $D1\Pi -X1\Sigma +$ and $E1\Sigma +-x1\Sigma +$ transitions in CuCl. The sample was vapourised in a high temperature nozzle and then cooled by expansion into a vacuum chamber. The observed rotational temperature was 15K and hyperfine structure due to the Cu nucleus was easily resolved in the D-X transition. The spectra have been analysed and fitted to appropriate effective hamiltonians and several molecular parameters determined. The implication of these values for the structure of CuCl is examined and in particular it is suggested that the D state conforms more closely to a $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Pi$ state rather than a $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Delta 1$ state, in contradiction to some recent theoretical calculations.