Dual Laser Produced Plasma Technique Research Articles

Extreme ultraviolet inner shell photoabsorption of iodine and gold ions

Photoabsorption spectra of iodine and gold plasmas were recorded using the dual laser produced plasma technique. In the case of iodine, the spectra were dominated by 4d excitation and contributions from stages up to four times ionized were observed. For gold, the spectra obtained could be assigned to 5p and 4f excitation in Au+ to Au4+. The main spectral features were identified by comparison with atomic structure calculations.

Analysis of the xuv photoabsorption spectrum ofAu2+,Au3+, andAu4+

The photoabsorption processes of ${\text{Au}}^{2+}$, ${\text{Au}}^{3+}$, and ${\text{Au}}^{4+}$ have been investigated experimentally and theoretically in the 70--127 eV region. Using the dual laser-produced plasma technique, the $4f$ and $5p$ photoabsorption spectrum has been recorded at 50 ns time delay and was found to be dominated by a great number of lines from $4f\text{\ensuremath{-}}5d$, $6d$ and $5p\text{\ensuremath{-}}5d$, $6s$ transitions, which have been identified by comparison with the aid of Hartree-Fock with configuration interaction calculations. The characteristic feature of the spectrum is that satellite lines from excited configurations containing one or two $6s$ electrons are more important than resonance lines, and with increasing ionization, satellite contributions from states with one $6s$ spectator electron gradually become more important than those with two $6s$ spectator electrons. Based on the assumption of a normalized Boltzmann distribution among the excited states and a steady-state collisional-radiative model, we succeeded in reproducing a spectrum which is in good agreement with experiment.

Vanishing resonances and excited populations: The4dphotoabsorption spectrum of Xe-likeLa3+and I-likeLa4+

The photoabsorption spectrum of Xe-like La{sup 3+} and I-like La{sup 4+} has been obtained in the extreme ultraviolet (euv) spectral region with the dual laser produced plasma technique. Photoexcitation from the 4d subshell is the dominant process in the 80-150 eV energy range. Strong discrete structure, corresponding to 4d{yields}np, mf (n>6, m>4) transitions in La{sup 3+} was observed at lower laser power densities, but with increasing laser flux the discrete features were suppressed and replaced by broad features in the 4d{yields}5p and 4d{yields}4f regions. This behavior can be attributed to the presence of absorption from excited states containing open 5p and 4f subshells in La{sup 3+} and the onset of similar absorption in La{sup 4+}.

Absolute photoionization cross-section measurements of the Kr I isoelectronic sequence

Photoionization spectra have been recorded in the $4s$, $4p$, and $3d$ resonance regions for the Kr I isoelectronic sequence using both the dual laser produced plasma (DLP) technique (at DCU) to produce photoabsorption spectra, and the merged ion beam and synchrotron radiation technique (at ASTRID) to measure absolute photoionization cross sections. Profile parameters are compared for the $4s\text{\ensuremath{-}}np$ resonances of ${\mathrm{Rb}}^{+}$ and ${\mathrm{Sr}}^{2+}$. Many $4p\ensuremath{\rightarrow}ns$, $md$ transitions are identified with the aid of Hartree-Fock calculations, and consistent quantum defects are observed for the various $ns$ and $md$ Rydberg series. Absolute single and double photoionization cross sections recorded in the $3d$ region for ${\mathrm{Rb}}^{+}$ and ${\mathrm{Sr}}^{2+}$ ions show preferential decay via double photoionization. This is only the second report to our knowledge where both the DLP technique and the merged-beam technique have been used simultaneously to record photoionization spectra, and the advantages of both techniques (i.e., better resolution in the case of DLP and values for absolute photoionization cross sections in the case of the merged-beam technique) are highlighted.

Discrete structure in the 4d photoabsorption spectra ofCs III, Cs IV and Cs V

XUV photoabsorption spectra of caesium, in ion stages up to Cs4+, have been obtained experimentally with the dual laser-produced plasma technique. From the results it can be inferredthat the 4d photoabsorption cross-section changes dramaticallyin appearance along the isonuclear sequence Cs throughCs4+. While the spectra of Cs, Cs+ and Cs2+ aredominated by a giant dipole 4d →εfresonance, discrete structure, which essentially increases inintensity with increasing ion stage, is also present below threshold. Between Cs2+ and Cs3+ much of the oscillator strength is abruptly transferred from the continuumto the discrete spectrum so that a few intense broad featuresdominate the spectra of Cs3+ and Cs4+. Multiconfiguration Hartree-Fock calculations successfullyaccount for this behaviour and permit identification of thediscrete features.

Discrete structure in the 4d photoabsorption spectrum of tellurium and its ions

The 4d inner-shell absorption spectra of Te, Te+, Te2+ and Te3+ have been recorded with the dual laser produced plasma technique. Discrete structure due to 4d5p transitions has been observed in the 37 - 45 eV region and identified using Hartree-Fock calculations within the superposition of configurations method. For comparisons of theoretical and experimental spectra, the method approximates a calculation of the resonant part of the photoionization cross section. It was also necessary, especially in the higher ion stages, to include absorption from excited states of the ground configurations. From these, synthetic spectra were produced which generally agree well with the experimental data.

Trends in 4d-subshell photoabsorption along the iodine isonuclear sequence: I, I+, and I2+

The 4d absorption spectra of I, ${\mathrm{I}}^{+}$, and ${\mathrm{I}}^{2+}$ have been observed in the 45--300-eV region using the dual laser-produced plasma technique. At lower energies each spectrum is dominated by intense 4d\ensuremath{\rightarrow}5p transitions, which are identified with the aid of multiconfiguration Hartree-Fock calculations. The excited states decay by direct autoionization involving 5s or 5p electrons and rates for the different processes and resulting linewidths were calculated and compared, where possible, with experiment. In the case of neutral iodine 4d\ensuremath{\rightarrow}6p transitions are also observed in the region close to the $^{2}$${\mathit{D}}_{5/2}$ threshold. The dominant feature in each spectrum, however, arises from 4d-f excitation, which evolves from a 4d-\ensuremath{\varepsilon}f shape resonance in neutral iodine to a feature containing discrete 4d\ensuremath{\rightarrow}nf transitions in ${\mathrm{I}}^{2+}$. \textcopyright{} 1996 The American Physical Society.

3d absorption spectra of Sr I through Sr IV.

The extreme ultraviolet photoabsorption spectra of neutral to three-times-ionized strontium have been recorded in a comprehensive series of experiments with the dual laser-produced plasma technique. Striking differences were found in the spectra, which can be attributed to the transfer of oscillator strength from 3d\ensuremath{\rightarrow}np to 3d\ensuremath{\rightarrow}nf transitions at ${\mathrm{Sr}}^{2+}$ due to nf wave-function contraction. In Sr and ${\mathrm{Sr}}^{+}$, 3d\ensuremath{\rightarrow}5p transitions dominate; in ${\mathrm{Sr}}^{2+}$, 3d\ensuremath{\rightarrow}nf transitions are most intense, while in ${\mathrm{Sr}}^{3+}$ the 4p subshell opens and 3d\ensuremath{\rightarrow}4p transitions are the strongest features. Partial cross sections for 3d\ensuremath{\rightarrow}\ensuremath{\varepsilon}f and 3d\ensuremath{\rightarrow}\ensuremath{\varepsilon}p photoionization were calculated and compared with experiment.

The 2p-subshell photoabsorption spectrum of Al+ in a laser-produced plasma

The authors have recorded the time-resolved photoabsorption spectra of aluminium plasmas in the 50-200 AA wavelength range using the dual laser produced plasma technique (DLPP). Absorbing plasmas were generated by focusing the output from a pulsed dye or a Q-switched ruby laser onto an aluminium slab target. The continuum backlight was provided by irradiating a tantalum rod with the output from a time-synchronized Q-switched Nd-YAG laser. Some of the spectra were recorded with the aid of a toroidal mirror. By combining time and space resolution the authors have been able to isolate almost exclusively Al+ and record its photoabsorption spectrum. They provide an analysis of 2p to nd, (n+1)s Rydbergs in Al+ based on multiconfiguration ab initio atomic structure calculations and quantum defects for the higher members of each series. They have also observed and tentatively classified a number of members of the 2p63s2 to 2p53s3p2 doubly excited transition array.

2p photoabsorption spectra of valence excited configurations in Al2+ and Si3+ observed in a dual laser produced plasma experiment

Using the dual laser produced plasma technique photoabsorption spectra of core excited autoionizing states in Al2+ (160-175 Å) and Si3+ (117-128 Å) have been recorded. Lines belonging to the 2p6 3p-2p5 3s3p and 2p6 3d-2p5 3s3d transition arrays have been assigned with the help of MCDF atomic structure calculations and previously classified transitions arising from the 2p6 3s ground state.

Ultraviolet Absorption of Refractory Elements by a Dual Laser Plasma Method

AbstractThe dual laser-produced plasma technique for the study of ionic absorption spectra has been developed by the use of two Q-switched ruby lasers to enable independent generation of the absorbing and back-lighting plasmas. Optical pulse handling is used in the coupling cicuits to enable reproducible pulse delays from 250 nsec. to 10 msec, to be achieved. At delay times > 700 nsec. spectra of essentially pure neutral species are observed. The technique is valuable, not only for obtaining the neutral spectra of highly refractory and/or corrosive materials but also for studying behaviour of ionic species as a function of time. Typical spectra are shown in Fig. 1.