Chemiluminescent reaction of Ba(3P) with N2O at hyperthermal collision energies: Rotational alignment of the BaO(A 1Σ+) product

ROSSA, M.; RINALDI, CA; JUAN CARLOS FERRERO

J.Chem.Phys

American Institue of Physics

Año: 2007 vol. 127 p. 64309 - 64309

The chemiluminescent reaction Ba (6s6p P3) + N2 O was studied at an average collision energy of 1.56 eV in a beam-gas arrangement. Ba (P3) was produced by laser ablation of barium, which resulted in a broad collision energy distribution extending up to ∼5.7 eV. A series of experiments was made to extract the Ba (P3) contribution to chemiluminescence from that corresponding to Ba 6 s2 S01 and 6s5d D3, which are the other two most populated states in the atomic beam. The fully dispersed polarized chemiluminescence spectra at 400-600 nm from the title reaction were recorded and assigned to a BaO molecule excited in the A +1 level. In addition, the average and wavelength-resolved degrees of polarization associated to the parallel BaO (A +1 →X +1) emission are reported. The analysis of the average polarization degree show that the BaO (A +1) product is significantly aligned, suggesting that the reaction mechanism is predominantly direct. The product rotational alignment was found to depend markedly on the emission wavelength, which revealed a negative correlation with the BaO (A +1) product vibrational state. On the basis of experimental and theoretical investigations on the reactions of N2 O with both the S01, D3, and P11 states of Ba and the lighter group 2 atoms, it is suggested that the Ba (P3) reaction involves a charge transfer at relatively short reagent separations and that restricted collision geometries at the highest velocity components of the broad distribution are necessary to rationalize the data. © 2007 American Institute of Physics.