Electronic Spectra of Diatomic Molecules

Abstract

It is appropriate to mention here that this project was originally directed by Professor Dr. M. Rafi who later on took an assignment at King Abdul A7iz university, Jeddah and it was assigned to the present principal investigator. In this project, we have taken up the emission and absorption studies of diatomic' molecules. It is known that the AE state of alkali hydride molecules has an abnormal character. The anharmonicity parameter (8-13) is negative for all the members of alkali hydrides in contrast to that for the rest of the molecules. We have, therefore, planned to carry out rotational and vibrational study of this state (in absorption)for molecules of hydrides of lithi.um, potassium and sodium near the dissociation energy which has not been done earlier. Despite the fact, that there should be a great number of electronic states, we find that data on many molecules consist of only few electronic states. An example is the bismuth molecule, where very few states (4-7) are known. Also, in absorption, molecules of lithium, potassium, bismuth, lithium-potassium have been studied. Several new electronic states have been found in these molecules. Band systems of hydrides of lithium, potassium and sodium molecules have been extended to higher vibrational states close to the dissociation limit. For these band systems rotational and vibrational analysis have been performed. Computer methods have been used to analyze the data.The new as well as improved values of the molecular parameters, thus determined, have been presented. Preliminary data have been taken on the spectra of oxides of aluminum, galium and indium. Also work is direced towards laser spectroscopic techniques. In particular, an experiment is being set up for laser induced fluorescence (LIF) spectroscopy of diatomic molecules. For this purpose, a Czerny-Turner type monochromator has been designed and fabricated(1).