Abstract

The invention and development of Fourier transform spectrometers (F.T.S.) in France, at Laboratoire Aimé Cotton, marked a turning point in the acquisition of high-quality spectroscopic data, mainly after implementation of the third generation apparatus (1). F.T.S. are now widely used in absorption spectroscopy (mid-and near infrared), but have also been used to study emission spectra. The first high resolution F.T. molecular electronic spectra recorded in emission were obtained in 1977 (2, 3). Shortly afterwards, laser induced fluorescence (L.I.F.) was recorded on an F.T.S. introducing selectivity via the excitation mechanism, and allowing fluorescence to be recorded from the laser line (visible) out to a few pm in regions inaccessible to other dispersive techniques (4,5). The main advantages of this technique are now well known (6). It has been proved invaluable in the study of the crowded spectra of high temperature molecules (e.g. transition metal halides), and in the characterisation of low lying excited electronic states. This paper uses examples of recent work on CuCl₂ to illustrate the advantages of using a cold source (free-jet expansion) and the use of optical-optical double resonance techniques to study lithium and iodine dimers.

© 1997 Optical Society of America