THE PURE ROTATIONAL SPECTRUM OF YTTRIUM MONOBROMIDE

The pure rotational spectrum of the X (1)Sigma(+) ground electronic st ate of yttrium monobromide has been measured. This is the first high-r esolution spectrum recorded for this molecule. Transitions in the grou nd and first excited vibrational states have been measured for both th e (YBr)-Br-79 and (YBr)-Br-81 isotopomers. Equilibrium rotational para meters have been determined and an equilibrium bond distance has been calculated. Vibrational parameters have been estimated. Hyperfine stru cture due to the bromine nuclei has been observed and nuclear quadrupo le and nuclear spin-rotation constants have been determined. These par ameters have been used to investigate the ionic character of the Y-Br bond and comparisons have been made to several alkali and alkaline ear th metal bromide species. (C) 1998 American Institute of Physics. [S00 21-9606(98)02337-X].