Infrared spectra of the reaction products of laser ablated lead atoms and oxygen molecules in condensing argon and nitrogen

Abstract

Reactions of laser ablated lead atoms with oxygen molecules in condensing argon and nitrogen streams gave the PbO, OPbO, Pb(O2), OPb(O2), PbOPb, Pb2O2, PbPb(O2), and Pb4O4 molecules. The formation of lead monoxide and linear dioxide molecules is the main difference with thermal evaporation experiments. The linear OPbO isomer was identified from oxygen-18 and lead (natural abundance) isotopic substitution in the strong antisymmetric stretching absorption at 764.8 cm−1; a weak ν1+ν3 combination band was observed at 1423.4 cm−1. Two bands [ν1=728.7 cm−1 (Ar) and 730.6 cm−1 (N2) and ν2=437.3 cm−1 (Ar) and 449.6 cm−1 (N2)] are assigned to the cyclic isomer Pb(O2) based on oxygen isotopic substitution. The position of the O–O stretching fundamental shows that Pb(O2) is a peroxidelike molecule. The secondary reaction Pb(O2)+Pb gives a large yield of cyclic Pb2O2 and allows observation of very strong antisymmetric Pb–O stretching fundamentals and combination bands with the two symmetric stretching fundamentals. Density functional frequency calculations with effective core potentials support assignment of the observed infrared absorptions.