P. Zimmermann

Open shells and multi-electron interactions: core level photoionization of the 3d metal atoms

This review covers the outer core level photoionization of the free 3d metal atoms from Sc to Cu. The experimental 3p, 3s and 2p photoemission and photoabsorption spectra are discussed. A comparison emphasizes common features and distinct differences. The interpretation of the data based on ab initio calculations reveals the influence of multi-electron interactions in the 3d metal atoms. We focus on the fundamental effects and main interactions which govern the electronic structure of these open shell atoms. (Some figures in this article are in colour only in the electronic version)

Lifetimes and oscillator strengths of neutral vanadium

Abstract Oscillator strengths of 105 V(I) lines in the spectral range 2800–6000 A were obtained by lifetime, emission, and hook measurements. Relative sets of ƒ-values were determined by combining emission measurements on a hollow cathode with hook measurements in a high temperature furnace, whereby no assumption concerning the plasma state is used and no temperature determination is required. The determination of the radiative lifetimes was performed by selective laser excitation of an atomic beam of vanadium and time-resolved observation of the reemitted fluorescence after the pulse. The absolute ƒ-values have an uncertainty of 12% on average. Both for the lifetimes and the ƒ-values a comparison with literature data is performed.

Lifetimes and oscillator strengths in the triplet system of ZnI

Selective laser excitation was used to measure the radiative lifetimes of the ZnI triplet states 4sns3S1(n=5–7) and 4snd3D3,3D2 and3D1(n=4–6). These states were excited from the metastable 4s4p3P states, which were collisionally populated in an atomic beam. The values are compared with the results of other experimental methods (beam-foil, pulsed electron excitation, Hanle effect) and with theoretical calculations. The corresponding oscillator strengths are discussed with respect to the astrophysical determination of the Zn photospheric abundance.

Lifetimes of the Si I 3p4s 1P1 and 3p3d 1P1 states

A beam of metastable silicon atoms was produced by collisional dissociation of silicon molecules and selectively excited by a pulsed dye laser. The lifetimes of the excited Si I states were directly determined from the fluorescence decay curve: τ(3p4s 1P1) = 4.1 (4) ns, τ(3p4s 3P2) = 4.4 (4) ns, τ(3p3d 1P1) = 8.1(5) ns.

Measurements of radiative lifetimes in Ta II and W II

Abstract New lifetime measurements in Ta II and W II are reported using selective laser excitation and time-resolved observation of the reemitted fluorescence. The ions were produced by the sputtering technique in a low-pressure discharge.

Lifetime measurements of stepwise collisional and radiative excited Mn I levels

Lifetime measurements of single fine-structure levels of the multiplets e8S, z6F, z4F and z4D of neutral manganese are described. The levels were excited stepwise by a pulsed dye laser from metastable levels populated by a discharge. The lifetimes were determined directly from the exponential decay of the fluorescence using the delayed coincidence technique. The results are compared with beam-foil data and used to derive absolute gf values by means of the branching ratios of Greenlee and Whaling (1979). Comparison of these gf values with the data compilation of the National Bureau of Standards shows large scatter. Using the results of the sun model of Holweger and Muller (1974) the mean photospheric solar Mn abundance has been determined from twelve different lines to AMn=5.47.

Lifetime measurements in the triplet system of Mg I

In an atomic beam the metastable 3s3p3P-states of Mg I were populated by electron impact. A pulsed tunable dye laser was used to excite the metastable atoms to the 3snd3D-(n=3–7) and to the 3sns3S1-states (n=4and 6). Observing the time dependence of the reemitted resonance light the lifetimes of these states were measured.

Lifetimes and oscillator strengths of singly ionized vanadium

Lifetimes of 12VII levels have been measured by using the technique of laser-excited fluorescence from sputtered metal vapour. The uncertainty is between 7–9%. For a determination of the individual transition probabilities the corresponding emission branching ratios have been measured on a high-current hollow-cathode in conjunction with a 1 m Fourier-transform spectrometer. Thef-values of 86 VII lines, which cover a spectral range 260–420 nm, have an uncertainty of about 12%. Comparison is made with literature data.

High-resolution photoion yield measurements of 'hollow' atomic lithium

Using monochromatized extreme-UV radiation from the undulator beamline BW3 at HASYLAB we have measured at high resolution (E/ Delta E approximately 7000) the Li+ photoion yield spectrum at excitation energies corresponding to transitions to double K-shell vacancy states. A number of such resonances including single-photon-three-electron excitations, e.g. 1s22s(2S) to 2p3(2p), have been observed for the first time. The spectrum is tentatively classified with the aid of Hartree-Fock calculations.

Rydberg series in the photoionization spectrum of Pd I

Abstract We present the first experimental investigation of the photoionization in Pd I using the synchroton radiation facility of the 800 MeV electron storage ring in Berlin (BESSY) and atomic beam technique. The experiments have been concentrated on the study of the Rydberg series of autoionizing levels 4 d 9 ( 2 D 3 2 )n p and nf which lie between the two 4d thresholds.