Knowledge Bank

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 $H2$ or $D2$. The observed bands have been classified into two electronic transitions. $B1\Pi -X1\Sigma +$ and $e3\Phi -a3\Delta$ (following the notation for YH in J. Chem. Phys. 101, 9283-9288 (1994). The laH bands observed in the $4000-4550cm-1$ region with Q-heads at $4533cm-1$ and $4429cm-1$ have been assigned as the 0-0 and 1-1 bands of the $B1\Pi -X1\Sigma +$ transition. To higher wavenumbers a group of bands observed in the $5600-6350cm-1$ region have been assigned into $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Phi 2-\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Delta l,\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Phi 3-\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Delta 2$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Phi 4$ sub-bands of a new electronic transition $e3\Phi -a3\Delta$. 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.