  We present new abundances derived from Cu I, Cu II, Zn I, and Zn II lines in
six warm (5766 < Teff < 6427 K), metal-poor (-2.50 < [Fe/H] < -0.95) dwarf and
subgiant (3.64 < log g < 4.44) stars. These abundances are derived from
archival high-resolution ultraviolet spectra from the Space Telescope Imaging
Spectrograph on board the Hubble Space Telescope and ground-based optical
spectra from several observatories. Ionized Cu and Zn are the majority species,
and abundances derived from Cu II and Zn II lines should be largely insensitive
to departures from local thermodynamic equilibrium (LTE). We find good
agreement between the [Zn/H] ratios derived separately from Zn I and Zn II
lines, suggesting that departures from LTE are, at most, minimal (< 0.1 dex).
We find that the [Cu/H] ratios derived from Cu II lines are 0.36 +/- 0.06 dex
larger than those derived from Cu I lines in the most metal-poor stars ([Fe/H]
< -1.8), suggesting that LTE underestimates the Cu abundance derived from Cu I
lines. The deviations decrease in more metal-rich stars. Our results validate
previous theoretical non-LTE calculations for both Cu and Zn, supporting
earlier conclusions that the enhancement of [Zn/Fe] in metal-poor stars is
legitimate, and the deficiency of [Cu/Fe] in metal-poor stars may not be as
large as previously thought.
