Electron impact excitation of the ground-state 3P fine-structure levels in atomic oxygen

Fine-structure collision strengths are calculated for transitions between the ground-state levels of atomic oxygen. The R -matrix method is used in which the (2p⁴) ³P, ¹D and ¹S terms are included as well as three pseudo-states chosen to represent the dipole polarizability of the ³P ground state. Very sophisticated configuration–interaction wavefunctions are used for the target states and a recoupling transformation to pair coupling is applied to the inner-region Hamiltonian matrix, with the ³P fine-structure energy levels being adjusted to match the observed splitting prior to diagonalization. Effective collision strengths 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.