LOW-ENERGY-ELECTRON SCATTERING BY OXYGEN MOLECULES .3. SPIN POLARIZATION EFFECTS IN ELASTIC-SCATTERING AND VIBRATIONAL-EXCITATION

The spin depolarization of transversely polarized electrons scattered by molecular oxygen in its X(3) Sigma(g)(-) ground state is reported. The R-matrix method has been used to calculate T-matrices for purely e lastic scattering X(3) Sigma(g)(-)(upsilon = 0 --> upsilon = 0) and vi brational excitation X(3) Sigma(g)(-)(upsilon = 0 --> upsilon = 1, 2, 3, 4) for energies in the range 4-13 eV. The present elastic results h ave been obtained by using the T-matrices of 10 scattering symmetries at the equilibrium geometry R = 2.3 a(0) and the vibrationally avenged T-matrices for the resonant (2) Sigma(u)(-) and (4) Sigma(u)(-) symme tries. The depolarization fractions are in better agreement with the e xperimental measurements than our earlier work in which the fixed-nucl ei T-matrices of all 12 scattering symmetries were used. For vibration al excitation, only the vibrationally averaged (4) Sigma(u)(-) and (2) Sigma(u)(-) symmetries were considered since the contributions to the cross sections from the other 10 symmetries are negligible. The resul ts show that exchange effects are much more significant in vibrational excitation than in elastic scattering.