Crossed-Beam Chemiluminescence Studies of Some Group IIa Metal Oxides

Abstract

Chemiluminescence from a beam of Group IIa metals traversing a scattering chamber filled with NO2 or N2O gas has been studied as a function of wavelength and pressure. The Ba+NO 2 and the Ba, Sr, and Ca + N 2O chemiluminescent reactions are first order in both reactants while Ca + NO 2 and Sr+NO 2 are quadratic in the NO2 pressure. Cross sections for beam attenuation are about 90–170 Å2 for reactions with NO2 (consistent with an electron-jump model), while those for N2O are 15–30 Å2. For the Ba+NO 2 reaction, the chemiluminescence has been assigned to the BaO A 1Σ−X 1Σ band system. From the resolved rotational structure it is concluded that with higher v′ excitation, the J′ distribution is characterized by a lower rotational temperature. A lower bound of 131.5 kcal/mole is placed on D 0 °(BaO). For certain reactions the chemiluminescence is weakly polarized. A model involving the partitioning of angular momentum between the rotation and recoil angular momenta of the products is proposed to account for the degree of polarization of the chemiluminescence.