Far- and mid-infrared emission spectroscopy of LiH and LiD

High-resolution Fourier transform spectra of LiH and LiD were recorded in the far-infrared region, 100-360 cm(-1), and the mid-infrared regions, 800-1200 cm(-1) and 2000-3000 cm(-1). A total of 261 pure rotational lines and 678 rovibrational lines were measured for the isotopomers (LiH)-Li-6(D) and (LiH)-Li-7(D). Molecular constants for the X-1 Sigma(+) ground state in the form of mass-dependent Dunham Y-ij's and mass-independent Dunham U-ij's were determined from a data set of 1476 lines, consisting of our measured line positions and previously reported microwave, millimeterwave, and infrared lines. An effective internuclear potential for the ground electronic state where the Born-Oppenheimer part is modeled as a parameterized modified-Morse function was also determined from a fit of the data. (C) 1998 Academic Press.