Transition probabilities based on sophisticated configuration interact
ion wave functions have been obtained for transitions between the fine
structure levels of the 26 lowest lying 2s(2)2p3, 2s2p4, 2s(2)2p3s, 2
s(2)2p(2)3p, 2s(2)2p(2)3d states of singly ionized oxygen. The calcula
tions were performed using the CIV3 code of Hibbert [1] and small empi
rical adjustments were introduced to the diagonal Hamiltonian matrix e
lements in order to achieve accurate energy splittings between the lev
els. The present results are believed to be the most accurate availabl
e and, for several allowed transitions, a significant departure from L
S coupling, due to relativistic effects, is found.