  We report on high spectral resolution observations of comet C/1999 S4
(LINEAR) obtained at McDonald Observatory in June and July 2000. We report
unequivocal detections of the O (1S) and O (1D) metastable lines in emission in
the cometary spectrum. These lines are well separated from any telluric or
cometary emission features. We have derived the ratio of the two red doublet
lines and show they are consistent with the predictions of the branching ratio.
We also derived a ratio of 0.06+/-0.01 for the green line flux to the sum of
the red line fluxes. This ratio is consistent with H2O as the dominant parent
for atomic oxygen. We have measured the widths of the lines and show that the
widths imply that there must be some parent of atomic oxygen in addition to the
H2O.
