Papers by Aneta Gójska
High Energy Density Physics, 2007
The Ka X-ray emission spectra of the low-density SiO 2 aerogel target bombarded by 48 Ca ions wit... more The Ka X-ray emission spectra of the low-density SiO 2 aerogel target bombarded by 48 Ca ions with initial energy of 11.4 MeV/u were measured with a high spectral and spatial resolution along 80% of the ion beam stopping path. The Si KaL 0 diagram and KaL n (up to n ¼ 5) X-ray satellite lines corresponding to the radiative decays of atomic states with one hole in the K-shell and n-holes in the L-shell were measured. Energy shifts of the KaL n satellites with respect to their diagram Ka lines were determined and compared with the results of multiconfiguration DiraceFock (MCDF) calculations. The experimental energy shifts are smaller than values obtained from free-ion MCDF theory assuming an empty M-shell. The influence of the valence M-shell configuration on the satellite X-ray spectra is discussed.
Physical Review A, 2010
This article presents a detailed analysis of the Kα x-ray spectra of Si induced by 11.4 MeV/u Ca ... more This article presents a detailed analysis of the Kα x-ray spectra of Si induced by 11.4 MeV/u Ca projectiles penetrating a low-density SiO 2 aerogel target measured with high spectral and spatial resolution at the UNILAC accelerator at GSI-Darmstadt. The low-density material used in the experiment was crucial for the space-resolved studies of the Si x-ray radiation (for different energies of stopping Ca ions). The stopping length of the 11 MeV/u Ca ions reaches up to 10 mm in the low-density SiO 2 aerogel, whereas in regular quartz solid targets it is about 100 times shorter. The analysis of the x-ray spectra emitted by the stopping medium has shown a high level of the L-shell ionization, especially in the later considered phase (E p ∼ 5 MeV/u) of the stopping process. It has been further demonstrated that the population of the highly ionized states produced in the ion-atom collisions can be substantially reduced in the time between the collision and the x-ray emission due to the very intense rearrangement processes occurring in Si situated in the chemical environment of oxygen atoms. Moreover, comparison of the experimental values of the Kα L-shell satellite energy shifts with the results of the multiconfiguration Dirac-Fock calculations allows us to find that Si valence electron configuration is enriched due to electron transfer from valence-electron-rich oxygen atoms into highly ionized silicon atoms. Our results indicate that the Coulomb explosion in a highly ionized track core is prevented by rapid neutralization in the femtosecond time scale.
Review of Scientific Instruments, 2010
Soft x-ray emission from a Mather-type plasma-focus device (PF-1000) operated at ∼400 kJ was meas... more Soft x-ray emission from a Mather-type plasma-focus device (PF-1000) operated at ∼400 kJ was measured. The high density and temperature plasma were generated by the discharge in the deuterium-argon gas mixture in the modified (high-current) plasma-focus configuration. A spherically bent mica crystal spectrograph viewing the axial output of the pinch region was used to measure the x-ray spectra. Spatially resolved spectra including the characteristic x-ray lines of highly ionized Ar and continua were recorded by means of an x-ray film. The x-ray emission of PF-1000 device was studied at different areas of the pinch.
Interactions of 150 MeV/amu 3 He ++ projectiles with solid gold targets have been studied at the ... more Interactions of 150 MeV/amu 3 He ++ projectiles with solid gold targets have been studied at the isochronous cyclotron of the RCNP in Osaka. The 3 He + ions resulting from capture of the target electrons to the projectile were observed with the use of large magnetic spectrograph, Grand Raiden, set at h = 0°with respect to the beam. The yield ratio of singly to doubly ionized helium ions emerging from thin gold foils, He + /He ++ , has been measured as a function of the foil thickness. Extrapolating the results to zero Au target thickness permits to determine the cross section values for electron stripping from 3 He + ions, r STRIP = 1.05 · 10 À17 cm 2 , and for electron capture to 3 He ++ ions, r CAP = 1.12 · 10 À25 cm 2 . The results obtained extend significantly the existing systematics for both processes to high (semi-relativistic) velocities. The collision strength deduced from the stripping cross sections deviates strongly from the theoretical predictions of Gillespie in absolute values as well as in the velocity dependence. It can, however, be well approximated by the simple Bohr formula for mid Z atoms. Also the capture data indicate the need to improve the theoretical approximations. A more detailed treatment of electrons captured from different shells in a high Z target is presumably needed. The astrophysical interest in the data of this kind for very light ions (hydrogen, helium) is indicated.
The Kb spectrum of 42 Mo bombarded by 20.8 MeV/amu carbon ions was measured with high-resolution ... more The Kb spectrum of 42 Mo bombarded by 20.8 MeV/amu carbon ions was measured with high-resolution using a transmission-type bent crystal spectrometer operated in the modified DuMond slit geometry. The M-shell satellites of the Kb 2 transition could be well resolved, whereas for the Kb 1;3 transitions only a broadening and shift of the line centroid was observed. The composite structure of the satellite lines which consist of many components that vary in energy and strength was analyzed using theoretical energies and relative intensities obtained from multiconfiguration Dirac-Fock calculations. From the data analysis average M-shell satellite-to-diagram line yield ratios were deduced for both the Kb 1;3 and Kb 2 transitions. For the Kb 2 transition for which the relative contributions of the 3s,p and 3d spectator vacancies to the observed Kb 2 M 1 satellite yield could be determined, separated X(Kb 2 M 1 1;2;3 ):X(Kb 2 M 0 ) and X(Kb 2 M 1 4;5 ):X(Kb 2 M 0 ) yield ratios could even be extracted.
This article presents a detailed analysis of the Kα x-ray spectra of Si induced by 11.4 MeV/u Ca ... more This article presents a detailed analysis of the Kα x-ray spectra of Si induced by 11.4 MeV/u Ca projectiles penetrating a low-density SiO 2 aerogel target measured with high spectral and spatial resolution at the UNILAC accelerator at GSI-Darmstadt. The low-density material used in the experiment was crucial for the space-resolved studies of the Si x-ray radiation (for different energies of stopping Ca ions). The stopping length of the 11 MeV/u Ca ions reaches up to 10 mm in the low-density SiO 2 aerogel, whereas in regular quartz solid targets it is about 100 times shorter. The analysis of the x-ray spectra emitted by the stopping medium has shown a high level of the L-shell ionization, especially in the later considered phase (E p ∼ 5 MeV/u) of the stopping process. It has been further demonstrated that the population of the highly ionized states produced in the ion-atom collisions can be substantially reduced in the time between the collision and the x-ray emission due to the very intense rearrangement processes occurring in Si situated in the chemical environment of oxygen atoms. Moreover, comparison of the experimental values of the Kα L-shell satellite energy shifts with the results of the multiconfiguration Dirac-Fock calculations allows us to find that Si valence electron configuration is enriched due to electron transfer from valence-electron-rich oxygen atoms into highly ionized silicon atoms. Our results indicate that the Coulomb explosion in a highly ionized track core is prevented by rapid neutralization in the femtosecond time scale.
The Ka X-ray emission spectra of the low-density SiO 2 aerogel target bombarded by 48 Ca ions wit... more The Ka X-ray emission spectra of the low-density SiO 2 aerogel target bombarded by 48 Ca ions with initial energy of 11.4 MeV/u were measured with a high spectral and spatial resolution along 80% of the ion beam stopping path. The Si KaL 0 diagram and KaL n (up to n ¼ 5) X-ray satellite lines corresponding to the radiative decays of atomic states with one hole in the K-shell and n-holes in the L-shell were measured. Energy shifts of the KaL n satellites with respect to their diagram Ka lines were determined and compared with the results of multiconfiguration DiraceFock (MCDF) calculations. The experimental energy shifts are smaller than values obtained from free-ion MCDF theory assuming an empty M-shell. The influence of the valence M-shell configuration on the satellite X-ray spectra is discussed.
The formation of the ͓1s2s͔ S states in heliumlike uranium ͑U 90+ ͒ has been studied in relativis... more The formation of the ͓1s2s͔ S states in heliumlike uranium ͑U 90+ ͒ has been studied in relativistic collisions of initially lithiumlike uranium ͑U 89+ ͒ ions with N 2 target molecules. By measuring projectile x-ray emission in coincidence with projectile ionization, a strong selectivity for the formation of the ͓1s2s͔ S states in heliumlike uranium is observed. This selectivity is found to be unaffected by the subsequent rearrangement of the atomic orbitals involved. By measuring the photon emission associated with the decay of the ͓1s2s͔ 1 S 0 and the ͓1s2s͔ 3 S 1 substates, we obtain for their relative population probabilities a ratio of close to 1. This finding deviates considerably from the assumption of a statistical distribution 2J +1.
The x-ray spectra produced in collisions of 98 MeV/u Li-like uranium ions with N2 molecules have ... more The x-ray spectra produced in collisions of 98 MeV/u Li-like uranium ions with N2 molecules have been studied. By measuring the decay photons associated with the capture process, experimental information for the formation of the excited [1s 2 2s2p 3/2 ] 1 P1 and [1s 2 2s2p 3/2 ] 3 P2 states in Be-like uranium has been obtained. It was found that relative probability for production of the P -states is close to statistical population law 2J + 1.
Interaction of radiation with helium atoms and/or ions is of interest in various astrophysical ap... more Interaction of radiation with helium atoms and/or ions is of interest in various astrophysical applications. The reverse reactions of fast 150 MeV/amu 3 He ++ ions with solid C targets have been studied at the isochronous cyclotron of the RCNP in Osaka. The singly ionized helium ions resulting from capture of the target electrons to the projectile were observed with the use of large magnetic spectrograph, Grand Raiden, set at θ = 0 • with respect to the beam. The yield ratios of singly-to-doubly ionized helium ions emerging from thin carbon foils, He + /He ++ , have been measured as a function of the foil thickness. Extrapolating the results to zero target thickness permits to determine the cross section values separately for electron stripping from 3 He + ions and for electron capture to 3 He ++ ions. The radiative and nonradiative contributions to the capture cross section were determined in a separate experiment in which the 84 keV (C.M.) photons were observed in coincidence with the He + ejectiles. The results are compared with theoretical predictions. Need for improved calculations is noted for all the three processes involved, i.e. for the radiative and non radiative electron capture as well as for the electron stripping.
Books by Aneta Gójska
Other papers by Aneta Gójska
A unique relief fibula dated to the Migration Period (first half of the sixth century) was found ... more A unique relief fibula dated to the Migration Period (first half of the sixth century) was found in Radziejów, Poland. This stray find changes previous opinions on the lack of settlement in central Poland at that time. As the find is the only one of such type in Poland, a special attention was paid to possible analogies, mainly finds from Scandinavia and Western Europe. The fibula underwent technological analyses in order to reveal its technology of manufacture. For this purpose, the chemical and elemental composition of the alloy was studied. Several physico-chemical complementary techniques such as optical microscopy (OM), scanning electron microscopy with energy dispersive X-ray (SEM–EDX) spectroscopy, energy dispersive X-ray fluorescence (ED-XRF) analysis, X-ray diffraction (XRD) analysis and micro-hardness testing (HV0.2) were used to study the technology of the find. The investigations revealed that this artefact was made from brass (4–17 wt% Zn) with an admixture of Sn (2–12 wt%). Two technologies were used: casting for the bow and forming for the part with the axle of the spring. The artefact's surface was tinned in the hot-dipping process. The physical structural analyses demonstrated that the artefact was cast and ornamented by surface stamping under a relatively low temperature (about 500 °C). Keywords Relief fibula. Migration Period. Scandinavian metal handicraft. Ancient metallurgy. SEM–EDX. ED-XRF. XRD
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