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 Å ( 6 s 6 p ^ { 2 } ^ { 2 } D _ { 3 / 2 } ) and 1433.9 Å ( 6 s ^ { 2 } 6 d ^ { 2 } D _ { 3 / 2 } ) .
We also report the first detection of the Pb ii \lambda 1203 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 \lambda 1203 , 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 \lambda 1433 ( 0.321 \pm 0.034 ) 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 \lambda 1433 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 .