Dual Laser Plasma Technique Research Articles

EUV photoabsorption spectrum of N-like fluorine using dual laser plasma technique

Employing the dual laser plasma technique, we measured the extreme ultraviolet (EUV) photoabsorption spectrum of F2+ ions, spanning the energy range from 53 to 93 eV with an energy resolution (E/ΔE) of 866. The measured spectrum is carefully analyzed by comparing with the available reference data and theoretical calculation using the Cowan code. We identify prominent transitions to the Rydberg series 2s22p2ns/nd and 2s2p3np from the ground level and remarkable transitions to the 2s22p2(1D)nd2D states from the 2s22p32D metastable level. Transition energies and line profile parameters are determined by fitting the identified absorption features. The calibration of the spectrometer with well-known transitions allows us to provide line positions for well-resolved resonances with an uncertainty of 20 meV. The reported experimental data of F2+ significantly contribute to the fundamental atomic database, offering valuable benchmarks for theoretical calculations with potential applications in astrophysics and plasma sciences.

The 5d-6p VUV Photoabsorption Spectrum of Bi+

The photoabsorption spectrum of Bi+ was measured in the wavelength range between 37 and 60 nm, using the dual laser plasma technique in which one plasma is used as the source of vacuum ultraviolet continuum radiation and the other plasma is used as the sample of atoms and/or ions to be probed. A number of features in the Bi+ spectrum was identified with the aid of the Cowan suite of atomic codes. The 5d → 6p transitions from the ground configuration (5d106s26p2) gave rise to the most prominent features in the measured spectrum. Transitions from low-lying excited states associated with the four excited configurations, 5d106s26p6d, 5d106s26p7s, 5d106s26p7p and 5d106s6p3, were found to make small contributions to the observed spectrum in the 47–50 nm spectral region. To the best of our knowledge, for Bi+, this spectral region is rather unexplored and spectroscopic data are absent from the literature.

Single photoionization of the Kr-like Rb ii ion in the photon energy range 22–46.0 eV

Abstract Single photoionization cross-sections for Kr-like Rb+ ions are reported in the energy (wavelength) range from 22 (564 Å) to 46 eV (270 Å). Theoretical cross-section calculations for this trans-Fe element are compared with measurements from the ASTRID radiation facility in Aarhus, Denmark and from the dual laser plasma technique, at respectively 40 and 35 meV FWHM energy resolution. In the photon energy region 22–32 eV the spectrum is dominated by excitation auto-ionizing resonance states. Above 32 eV the cross-section exhibits classic Fano window resonances features, which are analysed and discussed. Large-scale theoretical photoionization cross-section calculations, performed using a Dirac Coulomb R-matrix approximation are benchmarked against these high-resolution experimental results. Comparison of the theoretical work with the experimental studies allowed the identification of resonance features and their parameters in the spectra in addition to contributions from excited metastable states of the Rb+ ions.

Extreme ultraviolet photoabsorption spectra of the Ce VI–Ce X isonuclear sequence

The extreme ultraviolet photoabsorption spectra of cerium from five to nine times ionized have been recorded in the 70–120 eV region using the dual laser plasma technique. These represent the highest ion stages observed to date using this method. The spectra below 115 eV were found to be dominated by 4d → 5p transitions from the ground configurations of these ions and the resulting lines were identified with the aid of Hartree–Fock with configuration interaction calculations. Some features due to 4d → 5p transitions from the metastable configurations of ions Ce VI–Ce X were also observed.

3pphotoabsorption spectra ofMn2+andMn3+

Time-resolved extreme ultraviolet photoabsorption spectra of a manganese plasma have been recorded using the dual laser plasma technique. The 43-73 eV photon energy range is dominated by the 3p-3d giant resonance and to a lesser extent the 3p-4s resonances in both Mn{sup 2+} and Mn{sup 3+}, recorded at interplasma time delays of 80 and 30 ns, respectively. These experimentally observed resonances are well reproduced by synthetic spectra calculated using the Hartree-Fock method. The synthetic spectra allow for absorption from excited states of the Mn{sup 2+} and Mn{sup 3+} ions.

4d → 5p transitions in the EUV photoabsorption spectrum of La V, La VI and La VII

The photoabsorption spectra of La V, La VI and La VII have been recorded in the 85–96 eV region using the dual laser plasma technique. 4d → 5p transitions from their ground configurations were observed and identified with the aid of Hartree–Fock with configuration interaction calculations. The excited states were found to decay by autoionization involving 5s or 5p electrons and rates for the different processes and resulting linewidths were calculated and compared with experiment.

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.

4d → 5p transitions in the EUV photoabsorption spectrum of Ba IV, Ba V and Ba VI

The photoabsorption spectra of Ba IV–Ba VI have been recorded using the dual laser plasma technique. Discrete structure due to 4d → 5p transitions has been observed in the 75–85 eV region and identified using Hartree–Fock with configuration interaction calculations. The excited states decay by autoionization involving ejection of 5s or 5p electrons and rates for the different processes and resulting linewidths were also calculated. From these calculations, synthetic spectra were produced and show excellent agreement with the experimental data.

EUV photoabsorption spectra of Cd II and Cd III

The photoabsorption spectrum of singly ionized cadmium has been measured in the 23.6–110 eV region using the dual laser plasma technique. We have observed many of the 4d105s → 4d95s np, mf transitions (7 ⩽ n ⩽ 9, 4 ⩽ m ⩽ 9) for the first time and identified them with the aid of Hartree–Fock and quantum defect calculations. We also report a number of window resonances in the 27–40 eV region whose origins have not been determined, and the overall shape of the 4d photoionization spectrum. Finally, we have determined four new 4d9nl levels of Cd2+.

VUV/EUV ionising radiation and atoms and ions: dual laser plasma investigations

The interaction of ionising radiation with atoms and ions is a key fundamental process. This report concentrates on studies of photoexcitation/photoionisation using laser-produced plasmas as continuum sources and synchronised laser plasma plumes to provide the absorbing atom or ion species. Examples from studies of the interaction of ionising radiation with atoms and ions ranging from few-electron atomic and ionic systems to the many-electron high atomic number actinides are reviewed and illustrate the advantages and limitations of the Dual Laser Plasma technique.

4d→5p transitions in the extreme ultravioletphotoabsorption spectra of Sn II and Sn III

The photoabsorption spectrum of a tin laser-produced plasma has beenrecorded in the 23-33 eV region using the dual laser plasmatechnique. 4d→5p transitions from the4d105s25p ground state of Sn II and from the 4d105s2 ground and 4d105s5p excited states ofSn III were observed and new features identified with the aidof multiconfiguration Hartree-Fock calculations. The relativeintensities of transitions in Sn III indicate a departure fromlocal thermodynamic equilibrium conditions in the absorbing plasma.

Absorption spectroscopy of an expanding laser produced lithium plasma in the extreme ultraviolet using the Dual Laser Plasma technique

We describe the essential features of the Dual Laser Plasma (DLP) vacuum ultraviolet photoabsorption spectroscopy technique and the characteristics of our DLP apparatus. We show that the time- and space-resolved capabilities of this technique are suited to the monitoring of the dynamics of expanding plasma plumes in the regime used for pulsed laser deposition of materials. Examples of spectra showing the spatial and temporal evolution of a lithium plasma expanding in vacuum are presented. A model based on a self-similar expansion for the plume is developed and used to analyse the shape of absorption lines. Measurements in the photoionisation continuum of Li + are also presented.

3d Photoabsorption in Zn II, Ga III and Ge IV

The 3d photoabsorption spectra of Cu I-like Zn II, Ga III and Ge IV have been recorded in the 25-100 eV region using the dual laser plasma technique. The spectra are dominated by transitions of the type which have been identified by comparison with multiconfiguration Hartree-Fock calculations.

Measurement and analysis of the photoabsorption spectra of laser-produced Al and in the region of 2p-subshell excitation

The 2p-subshell photoabsorption spectra of atomic aluminium and singly ionized silicon, measured using the dual-laser plasma technique, are presented. The spectra are dominated by and one- and two-electron excitations, respectively. Relative photoabsorption cross sections, derived from the experimental spectra, are compared with computed theoretical cross sections. An interpretation is provided within the framework of the Hartree-Fock configuration-interaction calculations. It is found that mixing between core singly and doubly excited configurations strengthens with increasing atomic number at the beginning of the aluminium isoelectronic sequence. This observation is in contrast to our findings for the Mg-like isoelectronic species Mg, and (Sayyad M H et al 1995 J. Phys. B: At. Mol. Opt. Phys. 28 1715) in which such mixing weakens with increasing atomic number.

Measurement of the XUV photoabsorption spectra of atomic zinc and its ions : n = 1, 2, and 3 in the region of 3p-subshell excitation

Photoabsorption studies, using the dual laser plasma technique, have been initiated along the zinc isonuclear sequence as far as in the energy region corresponding to 3p-subshell electron excitation. For neutral, singly and doubly ionized zinc the 3d-subshell remains closed and excitations of the type 3p - ns have been found to predominate. The symmetric nature of the resonance profiles is evidence of the weak interaction of these discrete states with the underlying continua. The relatively large widths of the resonances can be interpreted as being mostly due to the nonradiative decay of the 3p core hole through both super and normal Coster - Kronig decay processes. The spectral signature of the `transition metal-like' 3p - 3d resonance is dramatically different, the asymmetric nature of which reflects the increased interaction between direct 3d photoionization and the discrete excitation processes. The main resonances in the spectra of , and have been parametrized and compared with calculations based on both single-particle and collective models.

The 3p photoabsorption spectra of K II and Ca III

The 3p photoabsorption spectra of K II and Ca III have been recorded in the 25-55 eV region using the dual laser plasma technique. With the help of calculations performed with the Cowan code and Rydberg series expansions, many 3p to ns, d transitions have been identified in these ions. Strong LS-term-dependent behaviour arising from 3d wavefunction contraction is seen to influence intensities and quantum defects in the 3p to nd series.

4f(1P) giant dipole resonance in La3+

Photoabsorption of free ${\mathrm{La}}^{3+}$ ions in the $4d$ excitation region has been measured using the dual-laser plasma technique. A dramatic strong and broad ${4d}^{9}4f{(}^{1}P)$ giant dipole resonance was observed. The interpretation of the results is provided using theoretical techniques which go beyond the independent particle approximation. In particular the strong term dependence for $4f{(}^{1}P)$ gives evidence of strong polarization effects for the description of the giant dipole resonance.

First observation of a photon-induced triply excited state in atomic lithium.

Using a dual laser plasma technique we have measured for the first time the photoabsorption spectrum of atomic lithium at energies corresponding to the simultaneous excitation of both 1s electrons. We have observed the main triply excited 1${\mathit{s}}^{2}$2s${(}^{2}$S)\ensuremath{\rightarrow}2${\mathit{s}}^{2}$p${(}^{2}$P) transition with Fano parameters ${\mathit{E}}_{0}$=142.32\ifmmode\pm\else\textpm\fi{}0.05 eV \ensuremath{\Gamma}=0.20\ifmmode\pm\else\textpm\fi{}0.04 eV, and q=-2.2\ifmmode\pm\else\textpm\fi{}0.6. Our experiment represents the first step in photoionization studies of this fundamental atomic system in which the motion of the three electrons in the field of the nucleus is so highly correlated.

XUV photoabsorption of laser-generated W and Pt vapours

The absorption spectra of atomic W and Pt have been recorded by the dual laser plasma technique in the range of the 4f and 5p excitations. Broad, strong and asymmetric 5p to 5d resonances dominate the spectra. The Pt 4f to 5d transitions give rise to prominent maxima superimposed on the high energy slope of the 5p to 5d resonances. Strong coupling to the 5d to in f continuum manifests itself in the asymmetric profiles of the resonances and the extremely low cross section below the 5p onset for atomic W. The experimental results are compared to spectra calculated within the many-body perturbation theory and the relativistic random-phase approximation.