The electronic emission spectra of LaH and LaD have been investigated in the 3 mu m-700 nm spectral region using a Fourier transform spectrometer. The molecules were excited in a lanthanum hollow cathode lamp operated with neon gas and a trace of hydrogen or deuterium. The bands observed in the 1 mu m-3 mu m region have been assigned into two new electronic transitions; A(1) Pi-X(1) Sigma(+) and d(3) Phi-a(3) Delta. The LaH bands with origins at 4533.5593(8) cm(-1) and 4430.1916(13) cm(-1) have been assigned as the 0-0 and 1-1 bands of the A(1) Pi-X(1) Sigma(+) transition. The rotational analysis of these bands provides the following principal molecular constants for the ground X(1) Sigma(+) state, B-e=4.080 534(80) cm(-1) and alpha(e)=0.077 39(10) cm(-1) and r(e)=2.031 969(20) Angstrom. To higher wave numbers, three subbands of LaH with origins at 5955.8568(16) cm(-1), 6238.3768(8) cm(-1), and 6306.6757(15) cm(-1) have been assigned as the (3) Phi(2)-(3) Delta(1), (3) Phi(3)-(3) Delta(2), and (3) Phi(4)-(3) Delta(3) subbands of the d(3) Phi-a(3) Delta electronic transition. The rotational analysis of the 0-0 and 1-1 bands of the (3) Phi(2)-(3) Delta(1), and (3) Phi(4)-(3) Delta(3), subbands and the 0-0, 1-1, and 2-2 bands of the (3) Phi(3)-(3) Delta(2) subband has been obtained and effective equilibrium constants for the spin components of the d (3) Phi and the a(3) Delta states have been extracted. Magnetic hyperfine structure was also observed in the a(3) Delta state. The rotational analysis of the corresponding LaD transitions has also been carried out and equilibrium constants for the ground and excited states have been determined. The singlet-triplet interval between the X(1) Sigma(+) state and the a(3) Delta state is not known but on the basis of ab initio calculation and by comparison with LaF and YH, we believe that the ground state of LaH is a(1) Sigma(+) state. (C) 1996 American Institute of Physics.
|Number of pages||8|
|Journal||Journal of Chemical Physics|
|Publication status||Published - 1 May 1996|
- POTENTIAL-ENERGY CURVES
- ELECTRONIC STATES