Knowledge Bank

“The absorption spectra of LiH and LiD have been photographed in the 2300-3200$\backslash AA$ region, using the 3rd order of a 21 foot grating spectrograph. Multiple reflection mirrors have been used in the absorption tube to obtain path lengths up to 16 meters. For each molecule a new ($\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Pi X1\sum +$) band system, showing a clear breaking off of the fine structure due to rotational predissociation, has been found. The rotational and vibrational analyses of both systems have been made and from the observed predissociation limits, the dissociation energies (Do) of LiH and LiD in the ground state have been found to be, $2,429\pm 0.001$ eV, and $2.451\pm 0.001$ eV, respectively.”