Knowledge Bank

We have recorded the electronic spectrum of copper dichloride, $CaCl2$, between 590 and 660nm in the gas phase. The sample was prepared as low temperatures using a free jet expansion from a heated nozzle. Under these conditions, rotational and even nuclear hyperfine structure was resolved. Many of the hands have been analysed in detail. Most of these involve the dominant isotope, $\mathrm{<mrow\; data-mjx-texclass="ORD">63</mrow>}Cu35Cl2$: but we have identified hands attributable of all six possible isotopomers. The parallel rotational structures of a linear molecule is shown by all hands, consistent with an electronic $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Pi u-3\Pi$ transition, in agreement with ab initio calculations. The majority of the bands studied are believed to involve the molecule in its ground vibrational state and are assigned as $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}\Pi 34-2\Pi 24$. From the lower state rotational constant for $Cu35Cl2$, the Cu-Cl bond length is calculated at $rc-\pi 203.614$ nm. The vibrational structure in the region studied is very complicated and no detailed vibrational assignments halve yet been made. Effort is being devoted towards identifying the (0,0) band of the electronic transition.