FOURIER TRANSFORM INFRARED EMISSION SPECTROSCOPY OF LaH AND LaD

Abstract

The electronic emission spectra of LaH and LaD were investigated in the 750 nm to $3 \mu m$ spectral region using a Fourier transform spectrometer. The bands were excited in a lanthanum hollow cathode lamp in the presence of a mixture of neon and $H_{2}$ or $D_{2}$. The observed bands have been classified into two electronic transitions. $B^{1}\Pi - X^{1}\Sigma^{+}$ and $e^{3}\Phi - a^{3}\Delta$ (following the notation for YH in J. Chem. Phys. 101, 9283-9288 (1994). The laH bands observed in the $4000-4550 cm^{-1}$ region with Q-heads at $4533 cm^{-1}$ and $4429 cm^{-1}$ have been assigned as the 0-0 and 1-1 bands of the $B^{1}\Pi - X^{1}\Sigma^{+}$ transition. To higher wavenumbers a group of bands observed in the $5600-6350 cm^{-1}$ region have been assigned into ${^{3}}\Phi_{2} - {^{3}}\Delta_{l}, {^{3}}\Phi_{3} - {^{3}}\Delta_{2}$ and ${^{3}}\Phi_{4}$ sub-bands of a new electronic transition $e^{3}\Phi - a^{3}\Delta$. The rotational analysis of the 0-0 and 1-1 bands of each transition has been carried out and the equilibrium constants for the ground and excited states have been obtained.