The FERRUM project: radiative lifetimes of intermediate-excitation states of Fe II measured in a fluorescence signal induced by laser pumping from a metastable state

A new collaborative program, the FERRUM project. aims at extending and impr oving the database of oscillator strengths for the astrophysical important Fe II spectrum. In this paper we report on the experimental method applied for measurements of radiative lifetimes of Fe II levels at intermediate exc itation (5-10 eV) that can be populated ba laser excitation from metastable states. The technique involves a laser-produced plasma as a source for met astable ions, a stimulated Brillouin scatttering cell for shortening the la ser pulse, and fast time resolved detection. We have applied the technique on two Fe II levels at about 7.5 eV and obtained the lifetimes: tau(z(4)S(3 /2)(0)) = 3.8(2) ns; tau(y(4)P(5/2)(0)) = 3.6(3) Its.