  We present the results of lifetime measurements made using beam-foil
techniques on levels of astrophysical interest in Pb II producing lines at
1203.6 A ($6s6p^{2}$ $^{2}D_{3/2}$) and 1433.9 A ($6s^{2}6d$ $^{2}D_{3/2}$). We
also report the first detection of the Pb II $\lambda1203$ line in the
interstellar medium (ISM) from an analysis of archival spectra acquired by the
Space Telescope Imaging Spectrograph (STIS) onboard the Hubble Space Telescope
(HST). The oscillator strengths derived from our experimental lifetimes for Pb
II $\lambda\lambda1203$, $1433$ are generally consistent with recent
theoretical results, including our own relativistic calculations. Our analysis
of high-resolution HST/STIS spectra helps to confirm the relative strengths of
the Pb II $\lambda\lambda 1203$, $1433$ lines. However, the oscillator strength
that we obtain for Pb II $\lambda1433$ ($0.321\pm0.034$) is significantly
smaller than earlier theoretical values, which have been used to study the
abundance of Pb in the ISM. Our revised oscillator strength for $\lambda1433$
yields an increase in the interstellar abundance of Pb of 0.43 dex over
determinations based on the value given by Morton, indicating that the
depletion of Pb onto interstellar dust grains is less severe than previously
thought.
