OPTICAL AND MAGNETIC RESONANCE STUDIES OF INORGANIC MOLECUAR CRYSTALS: URANIUM BOROHYDRIDE IN HAFNIUM BOROHYDRIDE

Author Institution: Department of Chemistry, Princeton UnivertsityMotivated by a desire to find and characterize inorganic molecular crystal systems, we have investigated the optical and EPR spectra of $U(BH_{4})_{4}$ in $Bf(BH_{4})_{4}$. These chemically mixed crystals are apparently substitutional;$U(BH_{4})_{4}$ maintains the full $T_{d}$ site symmetry to 2 k. By analyses of intensity patterns and temperature effects (300, 77 and 2 K) and by comparison of deuteride with hydride spectra from 5000 to $3000 cm^{-1}$ , we have identified at least 20 forced electric dipole (0-0) origins with several molecular vibrations built upon them. From the isotropic, single line at g = 2.00 in the EPR at 4 K, we have been assigned the ground state to be $T_{2}(^{3}H_{4})$. The electronic origins have been assigned from calculations and fit to two different free-ion crystal field models. The implications of these crystal field and vibrational analyss for actinide spectroscopy will also be discussed