  We present time-resolved spectroscopy of the soft X-ray transient XTE
J2123-058 in outburst. Spectral coverage of 3700-6700A was achieved spanning
two orbits of the binary. The strongest emission lines are HeII 4686A and
CIII/NIII 4640A (Bowen blend). Other weak emission lines of HeII and CIV are
present and Balmer lines show a complex structure, possibly contaminated by
HeII. HeII 4686A and CIII/NIII 4640A show different orbital light curves
indicating an origin in different regions. HeII 4686A profiles show a complex
multiple S-wave structure. Doppler tomography reveals this emission is not
associated with the companion star, and occurs at velocities too low for
Keplerian disk material. It can possibly be associated with overflowing or
splashing stream material. The optical spectrum approximates a steep blue
power-law, consistent with emission on the Rayleigh-Jeans tail of a black body
spectrum. Orbital modulations show no wavelength dependence; this is as
expected if both disk and companion star are hot enough for the peak of their
spectral energy distributions to be in the UV. The hot continuum and presence
of high-excitation emission lines indicate strong X-ray heating.
