Oscillator strength of the strongly "forbidden" Pb 6p(2) P-3(0) -> (6)p(2)P-3(1) transition at 1278.9 nm

The "forbidden" Pb 6p(2) P-3(o) --> 6p(2) P-3(1) line at 1278.9 nm is measu red by diode laser absorption in a resistively heated hot-pipe filled with a lead vapour and argon as buffer gas. The measurements performed at a temp erature of 1170 K and a lead number density of 2.4 x 10(15) cm(-3) yield th e oscillator strength f(F) = (4.5 +/- 1.1)x10(-7) which corresponds to a ra diative transition probability A(F) = (6.1+/-1.5) s(-1). Within the error b ars, the result is in agreement with theoretical data published by differen t authors.