Mass spectrometric investigation of gaseous YbH, YbO and YbOH molecules

The high-temperature gaseous molecules YbH, YbO and YbOH have been identified and their thermochemistry investigated by the Knudsen effusion mass spectrometry technique coupled with a controlled pressure gas inlet system. Solid ytterbium monosilicide and disilicide samples were made to react in the Knudsen cell with H-2(g) and H-2(9)/O-2(g); in these conditions, several gaseous species (Yb, YbO, YbH, YbOH, SiO, SiO2, H2O) were formed under equilibrium conditions. The temperature dependences of the partial pressures of the observed gaseous molecules were analyzed to derive the Yb-X bond energies (X=H, O, OH). Selected values are D-0(o)(Yb-H) = 179.4 +/- 2.0 kJ mol(-1), D-0(o)(Yb-O) = 384 +/- 10 mol(-1) and D-0(o)(Yb-OH) = 322 +/- 12 kJ mol(-1), and Delta(at)H(0)(o) (YbOH) = 746 +/- 12 kJ mol(-1). Density functional theory (DFT) calculations were also performed. Experimental and computational results are discussed and compared to previous data when available. The SiO/SiO2 high-temperature gaseous equilibrium was also observed. Copyright (C) 2005 John Wiley & Sons, Ltd.