Fe II lifetimes and transition probabilities

Fe II radiative lifetimes were measured applying the time-resolved nonlinear laser-induced fluoresence technique. We investigated 21 levels of up to 47000 1/cm. The uncertainties are typically 2-3%. The lifetimes provide an improved absolute scale to our branching fractions which were measured with a Fourier transform spectrometer and a high-resolution grating spectrometer and which have been published earlier. We report absolute transition probabilities of 140 Fe II lines in the wavelength range 220-780 nm. The overall uncertainties are estimated to be 6% for the strong and up to 26% for the weak transitions. The results are compared with recent experimental data from the literature. Our large set of accurate data can be used for a reliability check of theoretical data calculated for iron abundances in astrophysical plasmas

Radiative lifetimes of excited W II levels

Radiative lifetimes of 19 selected W II levels with energies between 36 000 cm-1 and 55 000 cm-1 have been measured with the time-resolved laser-induced fluorescence technique. The ions are generated in a hollow cathode discharge and stored in a linear Paul trap. Selected states are populated with tunable dye laser pulses and the subsequent fluorescence is measured by means of a 5 Gigasample transient digitizer and a fast photodetector with a risetime of 700 ps. By taking into account both the temporal profile of the laser pulses and the separately measured response function of the system, the lifetime can be determined from the full decay curve. A refined evaluation procedure, taking into account saturation effects in the signals, reduces the uncertainty in our data to around 1%

A linear Paul trap for radiative lifetime measurements on ions

A linear ion trap has been designed for collimation and storage of ions from an effusive particle beam generated in a hollow cathode discharge. The motivation is to measure radiative lifetimes on multiply ionized atoms by using the time-resolved laser-induced fluorescence technique. The trap has been tested on iron and tungsten ions both as an ion guide and also as a storing device. Radiative lifetimes have been measured in the trap with a remarkably higher signal-to-noise ratio than in the original effusive atom beam

Lifetimes, branching fractions, and oscillator strengths of doubly ionized Tungsten

A first small set of W III oscillator strengths has been obtained from combined lifetime and branching fraction measurements. The branching fractions in the wavelength region of 154-334 nm were measured with a Penning discharge and a Fourier transform spectrometer. Three levels have been calibrated on absolute scales with lifetimes measured with the time-resolved laser-induced fluorescence technique. The f-values derived have uncertainties of about 8% at best. A comparison with Cowan-code calculations is given since no other data are available in the literature

The FERRUM project: experimental lifetimes of highly excited FeII 3d(6)4p levels and transition probabilities

We report on measurements of radiative lifetimes in singly ionized iron of six 3d(6)4p levels between 61 512 and 64 041 cm(-1),using time resolved laser-induced fluorescence. Absolute oscillator strengths of 18 Fe II lines in the wavelength range from 2350 to 2800 Angstrom have been obtained by measuring branching fractions for the lines from two Fe II levels with a Fourier-transform spectrometer. The uncertainty in the lifetimes is between 8% and 13%, whereas the uncertainty of the f-values varies between 9% and 19%. A comparison with several previously published values is given