Dynamics by crossed-beam digital imaging: collisional energy effects on the Ba(1P1) + N2O→BaO(A′ 1Π, ′⩽3) + N2 differential reaction cross-section

Abstract

The dynamics of the excited-state Ba(¹P₁) + N₂O→BaO*(A′  ¹Π, ′⩽3) + N₂ reaction were investigated by crossed-beam digital imaging at 0.065 eV collision energy. To this end, the spatial (angular) distribution of the long-lived BaO*(A′  ¹Π, ′⩽3) product was imaged using a CCD camera. The analysis of the product angular distribution suggests a direct mechanism in which the excited-state BaO*(A′  ¹Π, ′⩽3) shows a backward scattering with the total energy of the reaction mostly channelled into product internal energy. A comparison between previous results obtained for the same reaction investigated at 0.155 eV (C. Rinaldi et al., Phys. Chem. Chem. Phys., 2000, 2, 723) and the present data suggests little change in the dynamics except for a modest enhanced forward character of the BaO* angular distribution when the reactant collision energy increases from 0.065 up to 0.155 eV. A comparison of the excited-Ba(¹P₁) and ground-state Ba(¹S₀) + N₂O reaction translational energy disposal with an impulsive and kinematic model prediction for atom–molecule reactions leads to the conclusion that kinematic factors play an essential role in both reactions. However, the ground-state reaction seems to proceed ia a more direct rebound mechanism with a predominance of collinear transition-state configurations.