Knowledge Bank

The group III transition metal monochlorides, YCl and Lacl, have been experimentally investigated by means of high resolution grating spectroscopy, Fourier transform spectroscopy, and various laser spectroscopic techniques. A complete survey on the spectrum of YCl has been carried out. Thermal emission, the emission from a dc discharge tube, the absorption, laser induced fluorescence (LIF) and wavelength-selected fluorescence excitation (WSFE) spectra of YCl have been studied. The electronic transitions $B1\Pi -X1\sum +,C1\sum +-X1\sum +,D1\Pi -X1\sum +,D1\Pi -A1\Delta ,J1\Pi -X1\sum +,K1\Pi -X1\sum +d3\Phi -a3\Delta$ and $g3\Delta -a3\Delta$ have been rotationally analyzed. The $X1\sum +-a3\Delta$ energy separation has also been probed by observation and analysis of the laser induced $D1\Pi -a3\Delta$ forbidden transition [1-5]. Spectroscopic investigations of LaCl have mainly coDcentrated in the infrared spectral region. The thermal emission spectrum of LaCl has been recorded using a Fourier transform spectrometer at high resolution. Two singlet and two triplet band systems have been observed and rotationally analyzed and assigned as due to the $B1\Pi -X1\sum +,C1\sum +-X1\sum 4d3\Phi -a3\Delta$ and $e3\Delta -a3\Delta$ transitions, respectively [6]. Molecular constants for all the involved electronic states have been determined.