P van Kampen

Wavelengths and energy levels of the 4d95s-4d95p transition array of Xe IX

The spectrum of Xe IX in the 400-1200 ? wavelength region has been obtained by observing the radiation emitted following electron capture by Xe9+ and Xe8+ ion beams incident on a He gas target. The xenon ions were produced by the Uppsala University ECR ion source. Many of the stronger lines were found to originate from 4d95s-4d95p transitions. All levels of the 4d95s and 4d95p configurations have been established. The analysis was assisted by MCDF calculations and isoelectronic comparison.

Time-integrated laser-induced plasma spectroscopy in the vacuum ultraviolet for the quantitative elemental characterization of steel alloys

This paper demonstrates that time-integrated space-resolved laser-induced plasma spectroscopy (TISR-LIPS) is a useful technique in the vacuum ultraviolet (VUV) for the quantitative determination of the carbon content in steels. The standard reference samples used were carbon-iron alloys containing a relatively wide concentration range of carbon (0.041-1.32%). In the experiments the output of a Q-switched Nd:YAG (1064?nm) laser, with approximately a 1?J maximum output pulse energy and approximately a 12?ns temporal pulse width, was focused onto the surface of each sample (under vacuum) in order to produce the emitting plasma. A fore-slit mounted in the target chamber allowed spatially-resolved spectral measurements in the axial direction of the plasma and provided emission lines that were almost free of the background continuum. A 1?m normal incidence vacuum spectrometer, equipped with a 1200 grooves mm-1 concave grating and a micro-channel plate/photodiode array detector combination, was used as the detection system. A particularly interesting feature of this work is the demonstration that VUV spectroscopy allows ionic lines to be used and linear calibration curves were obtained for the five carbon spectral lines (from C+ and C2+) under investigation. The limits of detection for all lines were determined; the lowest detection limit (87?10?ppm) was obtained from the C2+ 97.70?nm line, which compares favourably with the only available value in the literature of 100?ppm.

Metastable state contributions to the measured 3p photoabsorption spectrum of Cr+ ions in a laser-produced plasma

Recently, the spectrum of singly ionized chromium has come under theoretical scrutiny by Dolmatov (1996 J. Phys. B: At. Mol. Opt. Phys. 29 L673) and also by Donnelly et al (1997 J. Phys. B: At. Mol. Opt. Phys. 30 L285). Both of these theoretical investigations, employing the spin-polarized RPAE (SPRPAE) and R-matrix techniques, respectively, concerned the 3p photoabsorption cross section from the 3d5 6S5/2 ground state of Cr+. The two calculations are consistent with each other and agree with the previously reported experimental data for the 3p4s resonances and the onset of the 3p3d giant resonance (Costello 1991 Phys. Rev. A 43 1441). However, beyond the peak of the giant resonance, both calculations result in cross sections which differ considerably from the experimental data. From further dual-laser plasma experiments carried out under different spatio-temporal conditions and atomic structure calculations on metastable states this discrepancy can be ascribed to the presence of metastable excited singly ionized chromium within the plasma.

Vacuum-UV absorption spectrum of a laser-produced chromium plasma: 3p-subshell photoabsorption by Cr2+ ions

The dual laser plasma photoabsorption technique has been used to measure the time-resolved vacuum-UV photoabsorption spectrum of a chromium plasma. Resonant photoabsorption cross sections, constructed with the aid of Hartree-Fock calculations, and weighted in accordance with the plasma temperature, have been used to produce the synthetic Cr2+ spectra. The relevant plasma temperature and ionization balance are obtained from simple analytical models for various times during the expansion phase of the plasma plume. The experimental spectra taken at delays of 32, 62 and 90 ns compare well with Cr2+ spectra computed for corresponding predicted temperatures. It is found that in order to produce synthetic spectra that match experiment well, it is necessary to take into account absorption from many states belonging to the Cr2+ ground state configuration 3p63d4, while states from the nearest metastable configuration 3p63p34s make a negligible contribution.

4d photoabsorption spectra of Indium (In II?In IV)

The 4d photoabsorption spectra of singly to triply ionized indium have been recorded using the dual laser plasma technique in the 24.5–55 eV photon energy range. The data substantiate and add to previously classified lines in In II and In IV while many new lines are tentatively identified in In III. Transitions were assigned with the aid of Hartree–Fock calculations.

On the 3p-subshell photoabsorption spectra of iron-group ions: the case of Mn2+

The photoabsorption spectrum of doubly ionized manganese in the 45–75 eV photon energy range, where inner-shell 3p–3d and 3p–4s (and higher 3p–nl) transitions are induced, has been measured using a dual laser plasma technique. It compares favourably with the theoretical cross-section profile of Dolmatov (1996 J. Phys. B: At. Mol. Opt. Phys. 29 L687) and confirms his prediction that, between Mn+ and Mn2+, not only do the 3p–4s resonances swap over to the high energy side of the giant 3p–3d resonance but also that this reordering has significant effects on resonance profiles in doubly ionized manganese.

Matrix elements for photoionization in xenon derived from coincidence electron spectrometry

The magnitudes and relative phases of the matrix elements pertaining to photoionization in xenon at 132.2 eV photon energy have been derived from observables in an angle-resolved electron spectrometry experiment. The observables in question are the partial cross section, the angular distribution parameter of the photoelectron, the alignment parameter of the photoion, and the angular correlation between the photoelectron and the coincident Auger electron. Difficulties in extracting the desired matrix elements from these observables are discussed. Despite these difficulties, a set of matrix elements and relative phases could be extracted which is in good agreement with all experimental observables and also fulfils the constraint that spin - orbit effects in the photoelectrons partial waves be negligible. This data set differs significantly from theoretical predictions from relativistic random-phase calculations.

The 5d photoabsorption spectra of Pb III and Bi IV

The photoabsorption spectra of lead and bismuth ions have been recorded using the dual laser plasma (DLP) technique in the photon energy range 30–66 eV. The experimental observations and theoretical calculations are focused on the 5d inner-shell excitations of the Hg I like ions of lead (Pb III) and bismuth (Bi IV). With the aid of Hartree–Fock calculations in the jj coupling scheme, we have identified over 30 new lines in both ions. As a result of the new measurements in Bi IV, the previously determined first ionization potential of Bi III has been increased from 45.32 eV to 45.36 eV.

4d photoabsorption spectra of Sn II and Sn IV in the 30–65 eV region

EUV photoabsorption spectra of tin ions Sn II and Sn IV have been recorded using the dual laser-produced plasma (DLP) technique in the 30–65 eV region. It is known from previous studies by Lysaght et al (2005 Phys. Rev. A 72 014502), in the 30–100 eV domain, that gradual 4f contraction along the isonuclear sequence of Sn I through Sn IV results in a redistribution of the oscillator strength from the continuum to the pseudo-discrete 4d → f channels, with many intense absorption lines dominating the spectra of Sn IV. Using Hartree–Fock with configuration interaction calculations allows us to successfully account for, and permits identification of, pseudo-discrete 4d → np, nf features within the spectra of Sn II and Sn IV.

Vacuum-ultraviolet resonant photoabsorption imaging of laser produced plasmas

We present results from a vacuum-ultraviolet (VUV) “photoabsorption imaging” technique based on the measurement of the time and space resolved absorption of a quasimonochromatic VUV beam from a laser plasma light source. The use of VUV radiation as a probe beam permits direct access to resonance lines of (singly and more highly charged) ions and also to the resonant and nonresonant continua of atoms and ions. In this experiment we have confined ourselves to measurements using the 3p–3d resonances of Ca, Ca+, and Ca2+ as markers of the temporal and spatial distribution of ground state atoms and ions in an expanding laser plasma plume. We show how time resolved column density maps may be extracted from such images. In addition we have extracted plasma plume velocities from the data, which compare well with an analytical laser ablation model.