INFRARED-SPECTRA OF THE REACTION-PRODUCTS OF LASER-ABLATED LEAD ATOMSAND OXYGEN MOLECULES IN CONDENSING ARGON AND NITROGEN

Reactions of laser ablated lead atoms with oxygen molecules in condens ing argon and nitrogen streams gave the PbO, OPbO, Pb(O-2), OPb(O-2), PbOPb, Pb2O2, PbPb(O-2), and Pb4O4 molecules. The formation of lead mo noxide and Linear dioxide molecules is the main difference with therma l evaporation experiments. The linear OPbO isomer was identified from oxygen-18 and lead (natural abundance) isotopic substitution in the st rong antisymmetric stretching absorption at 764.8 cm(-1); a weak v(1) + nu(3) combination band was observed at 1423.4 cm(-1). Two bands [nu( 1) -728.7 cm(-1) (Ar) and 730.6 cm(-1) (N-2) and nu(2)=437.3 cm(-1) (A r) and 449.6 cm(-1) (N-2)] are assigned to the cyclic isomer Pb(O-2) b ased on oxygen isotopic substitution. The position of the O-O stretchi ng fundamental shows that Pb(O-2) is a peroxidelike molecule. The seco ndary reaction Pb(O-2)+Pb gives a large yield of cyclic Pb2O2 and allo ws observation of very strong antisymmetric Pb-O stretching fundamenta ls and combination bands with the two symmetric stretching fundamental s. Density functional frequency calculations with effective core poten tials support assignment of the observed infrared absorptions. (C) 199 6 American Institute of Physics