  Radiative lifetimes from laser-induced fluorescence measurements, accurate to
about +/- 5 percent, are reported for 41 odd-parity levels of Hf II. The
lifetimes are combined with branching fractions measured using Fourier
transform spectrometry to determine transition probabilities for 150 lines of
Hf II. Approximately half of these new transition probabilities overlap with
recent independent measurements using a similar approach. The two sets of
measurements are found to be in good agreement for measurements in common. Our
new laboratory data are applied to refine the hafnium photospheric solar
abundance and to determine hafnium abundances in 10 metal-poor giant stars with
enhanced r-process abundances. For the Sun we derive log epsilon (Hf) = 0.88
+/- 0.08 from four lines; the uncertainty is dominated by the weakness of the
lines and their blending by other spectral features. Within the uncertainties
of our analysis, the r-process-rich stars possess constant Hf/La and Hf/Eu
abundance ratios, log epsilon (Hf/La) = -0.13 +/- 0.02 (sigma = 0.06) and log
epsilon (Hf/Eu) = +0.04 +/- 0.02 (sigma = 0.06). The observed average stellar
abundance ratio of Hf/Eu and La/Eu is larger than previous estimates of the
solar system r-process-only value, suggesting a somewhat larger contribution
from the r-process to the production of Hf and La. The newly determined Hf
values could be employed as part of the chronometer pair, Th/Hf, to determine
radioactive stellar ages.
