R-matrix calculation of differential cross sections for low-energy electron collisions with ground and electronically excited state O2 molecules

摘要

Differential cross sections for electron collisions with the O$_2$ moleculein its ground ${X}^{3}\Sigma_g^-$ state, as well as excited ${a}^{1}\Delta_g$and ${b}^{1}\Sigma_g^+$ states are calculated. As previously, the fixed-bondR-matrix method based on state-averaged complete active space SCF orbitals isemployed. In additions to elastic scattering of electron with the O$_2$${X}^{3}\Sigma_g^-$, ${a}^{1}\Delta_g$ and ${b}^{1}\Sigma_g^+$ states, electronimpact excitation from the ${X}^{3}\Sigma_g^-$ state to the ${a}^{1}\Delta_g$and ${b}^{1}\Sigma_g^+$ states as well as '6 eV states' of${c}^{1}\Sigma_u^{-}$, ${A'}^{3}\Delta_u$ and ${A}^{3}\Sigma_u^{+}$ states isstudied. Differential cross sections for excitation to the '6 eV states' havenot been calculated previously. Electron impact excitation to the${b}^{1}\Sigma_g^+$ state from the metastable ${a}^{1}\Delta_g$ state is alsostudied. For electron impact excitation from the O$_2$ ${X}^{3}\Sigma_g^-$state to the ${b}^{1}\Sigma_g^+$ state, our results agree better with theexperimental measurements than previous theoretical calculations. Our crosssections show angular behaviour similar to the experimental ones fortransitions from the ${X}^{3}\Sigma_g^-$ state to the '6 eV states', althoughthe calculated cross sections are up to a factor two larger at large scatteringangles. For the excitation from the ${a}^{1}\Delta_g$ state to the${b}^{1}\Sigma_g^+$ state, our results marginally agree with the experimentaldata except for the forward scattering direction.