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DOI: 10.1039/A904195H (Paper) Reference Section for: Phys. Chem. Chem. Phys., 1999, 1, 3731-3735

Temperature dependent rate constants for the reactions of gas phase lanthanides with CO2

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Mark L. Campbell

Abstract

The reactivity of the gas phase lanthanide atoms Ln (Ln=La–Yb with the exception of Pm) with CO2 is reported. Lanthanide atoms were produced by the photodissociation of [Ln(TMHD)3] and detected by laser-induced fluorescence. For all the lanthanides studied with the exception of Yb, the reaction mechanism is bimolecular abstraction of an oxygen atom. The bimolecular rate constants (in molecule-1 cm3 s-1) are described in Arrhenius form by: k[Ce(1G4)]=(3.4±1.0)×10-10 exp(-3.5±1.0 kJ mol-1/RT); Pr(4I9/2), (2.5±0.4)×10-10 exp(-7.9±0.7 kJ mol-1/RT); Nd(5I4), (3.3±0.6)×10-10 exp(-12.0±0.8 kJ mol-1/RT); Sm(7F0), (1.7±0.8)×10-10 exp(-15.8±1.8 kJ mol-1/RT); Eu(8S7/2), (6.6±2.3)×10-10 exp(-39.2±1.6 kJ mol-1/RT); Gd(9D2), (1.1±0.3)×10-10 exp(-5.8±0.9 kJ mol-1/RT); Tb(6H15/2), (1.1±0.3)×10-10 exp(-10.8±1.2 kJ mol-1/RT); Dy(5I8), (4.0±0.7)×10-10 exp(-30.3±0.7 kJ mol-1/RT); Ho(4I15/2), (3.7±1.1)×10-10 exp(-33.1±1.3 kJ mol-1/RT); Er(3H6), (5.8±2.5)×10-10 exp(-36.9±2.0 kJ mol-1/RT); Tm(2F7/2), (1.1±0.5)×10-10 exp(-45.4±2.3 kJ mol-1/RT) where the uncertainties represent ±2σ. Yb(1S0) is unreactive with CO2 below 623 K. The reaction barriers are found to correlate to the energy required to promote an electron out of the 6s subshell.

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