ELECTRON-IMPACT EXCITATION OF THE GROUND-STATE P-3 FINE-STRUCTURE LEVELS IN ATOMIC OXYGEN

Fine-structure collision strengths are calculated for transitions betw een the groundstate levels of atomic oxygen. The R-matrix method is us ed in which the (2p(4)) P-3, D-1 and S-1 terms are included as well as three pseudo-states chosen to represent the dipole polarizability of the P-3 ground state. Very sophisticated configuration-interaction wav efunctions are used for the target states and a recoupling transformat ion to pair coupling is applied to the inner-region Hamiltonian matrix , with the P-3 fine-structure energy levels being adjusted to match th e observed splitting prior to diagonalization. Effective collision str engths are obtained by integrating over a Maxwellian distribution and the rate coefficient of the cooling of electron gas is determined. The cooling rates are significantly lower than those currently available, in confirmation of the result deduced from measurements of the Earth' s ionosphere electron gas.