Oxidation reactions of lanthanide cations with N2O and O-2: Periodicities in reactivity

The oxidation reactions of all of the lanthanide cations (except Pm+) with N2O and O-2 have been investigated using the inductively coupled plasma sel ected-ion flow tube (ICP/SIFT) technique. Lanthanide cations were generated in an inductively coupled plasma (ICP) ion source. Observations are report ed for the reactions of La+, Ce+, Pr+, Nd+, Sm+, Eu+, Gd+, Tb+, Dy+, Ho+, E r+, Tm+, Yb+, and Lu+ with N2O and O-2 at room temperature (295 +/- 2 K) in helium at a total pressure of 0.35 +/- 0.02 Torr. Measured reaction rates varied from close to the predicted ion-molecule collision rate down to less than 0.1% efficiency. Observations are rationalized in terms of reaction t hermodynamics and electronic structure effects. The efficiency for the reac tions with N2O was found to decrease as the energy required to promote the metal-ion electron from the 4f(n)5d(0)6s(1) to the 4f(n-1)5d(1)6s(1) config uration increases. Remarkable and different Arrhenius-like correlations are found in the N2O reactivity of the early and late lanthanide cations with this electron promotion energy.