Abstract
Fine-structure collision strengths are calculated for transitions between the ground-state levels of atomic oxygen, 3Pe2, 3Pe1 and 3Pe0, and comparisons are made with other calculations. The R-matrix method is used in which the (2p4)3P, 1D and 1S terms are included as well as three pseudostates, 3So, 3Po, and 3Do, chosen to represent the dipole polarisability of the 3P ground state. Configuration interaction wavefunctions are used for the target states. A recoupling transformation to pair coupling is applied to the inner-region Hamiltonian matrix, and before diagonalisation the 3P fine-structure energy levels are adjusted to match the observed splitting. Thus the kinematics of the continuum electron are correctly accounted for. The threshold behaviour of the fine-structure collision strength for oxygen is established for the first time. By integrating the collision strength over a Maxwellian distribution, effective collision strengths are calculated for electron temperatures in the range from 10000 down to 50 K.