Journal of Physics B: Atomic, Molecular and Optical Physics, 2016
Experimental and theoretical results are reported for single-photon single ionization of and W3+ ... more Experimental and theoretical results are reported for single-photon single ionization of and W3+ tungsten ions. Experiments were performed at the photon–ion merged-beam setup of the Advanced Light Source in Berkeley. Absolute cross sections and detailed energy scans were measured over an energy range 20–90 eV at a bandwidth of 100 meV. Broad peak features with widths typically around 5 eV have been observed with almost no narrow resonances present in the investigated energy range. Theoretical results were obtained from a Dirac–Coulomb R-matrix approach. The calculations were carried out for the lowest-energy terms of the investigated tungsten ions with levels for and for . Assuming a statistically weighted distribution of ions in the initial ground-term levels there is good agreement of theory and experiment for ions. However, for ions at higher energies there is a factor of approximately two difference between experimental and theoretical cross sections.
A crossed charged beam technique was employed in the investigation reported. The ion beam was cro... more A crossed charged beam technique was employed in the investigation reported. The ion beam was crossed at right angles by a magnetically confined electron beam. Cross sections were determined as a function of electron impact energy. Considerable structure in the excitation cross section appears immediately above the threshold. It is pointed out that a primary application of cross sections is related to the calculation of plasma rate coefficients.
Cross sections for the photoionization ͑PI͒ of Sc 2ϩ ions with ͓Ar͔3d ground-state configuration ... more Cross sections for the photoionization ͑PI͒ of Sc 2ϩ ions with ͓Ar͔3d ground-state configuration have been measured by employing the merged ion-photon beams method. The Sc 2ϩ ions were produced from metallic vapor in an electron cyclotron resonance ion source, and the photon beam was generated by an undulator in the electron-synchrotron storage ring of the advanced light source of the Lawrence Berkeley National Laboratory. The experimental photon energy range 23-68 eV encompasses the direct 3d and 3p photoionization thresholds. The experimental photoion spectrum is dominated by autoionizing resonances due to 3p excitations predominantly decaying via Coster-Kronig and super-Coster-Kronig transitions. Individual resonances located around EϷ40.2 eV have been measured with an instrumental energy spread ⌬E as low as 1.2 meV, corresponding to a resolving power of E/(⌬E) around 33 500. The fractions of metastable ions in the Sc 2ϩ ion beam are obtained by comparing the photoionization cross section with the recently measured ͓Schippers et al., Phys. Rev. A 65, 042723 ͑2002͔͒ cross section for the time-reversed process of photorecombination of Sc 3ϩ ions. Absolute strengths of several 3p 5 3d 2 and 3p 5 3d 4s PI resonances have been determined. They are the same as the corresponding resonance strengths for isoelectronic Ca ϩ ions.
Measurements of absolute total cross sections for electron capture by C[sup 3+] in collisions wit... more Measurements of absolute total cross sections for electron capture by C[sup 3+] in collisions with ground-state hydrogen and deuterium are reported in the energy range 0.3--3000 eV/u. In general, good agreement is obtained with published experimental measurements at the lower (10--110 eV/u) and higher ([gt]1 keV/u) collision energies. However, the improved accuracy and the large energy range of these measurements made possible by the merged-beams technique indicate an energy dependence different than was suggested by interpolating previous published and unpublished measurements and by a theoretical calculation that attempted to reconcile the previous low- and high-energy total-capture cross-section data. The present measurements above 100 eV/u show excellent agreement with a more recent 22-state molecular-orbital calculation that predicts slight structure in the cross section at collision energies between 1000 and 2000 eV/u. Below 100 eV/u, the present measurements, which were performed with deuterium, deviate from an energy dependence suggested by earlier hydrogen measurements and by fully quantal calculations.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1991
DE91 001214 7b quantitatively study electron capture during collisions of multiply charged ions w... more DE91 001214 7b quantitatively study electron capture during collisions of multiply charged ions wit.h neutral atoms at near-thermal energies, ke V-enerqy multicharged ion beams are rTterged with ground-state beams of H or D at.ores of chosen, velocity such. that collisions tn the relative energy range I-I000 eV/ainu result. Recent. data for 0 a4, 04+ 4-H(D) are presented and compared with, theoretical pred;_ions. Recently complet2d modificationsto the apparatus are described that will provide a significant improvement in, signal-to-background and angular collection. These improvements will allow measurements to be extended to lower energies, where effects due to the ion-induced dipole attraction may be evident, DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government, Neither the United States Government nor any agency thereof, nor any of their ptlbli.';h t_r rcl'q'_*:
Journal of Physics B: Atomic, Molecular and Optical Physics, 2012
Absolute single photoionization cross-section measurements of Se3+ and Se5+ ions were performed u... more Absolute single photoionization cross-section measurements of Se3+ and Se5+ ions were performed using monochromatized synchrotron radiation and the photo-ion merged-beams technique. Se3 + measurements were made at a photon energy resolution of 20 ± 3 meV from 41.90 to 54.56 eV, spanning the 2P1/2 ground state ionization threshold. Numerous autoionizing resonances arising from both the 2P1/2 ground state and 2P3/2 metastable state are identified using quantum defect analysis. For Se5 +, measurements were made at a photon energy resolution of 60 ± 10 meV from 81 to 101 eV, spanning the 2S1/2 ground state ionization threshold, and at a photon energy resolution of 28 ± 3 meV from 100.175 to 106.675 eV in a region rich with autoionizing resonances. The direct ionization threshold of the Se5 +2S1/2 ground state is experimentally determined to be 81.780 ± 0.010 eV.
Journal of Physics B: Atomic, Molecular and Optical Physics, 2010
Absolute cross sections for the K-shell photoionization of groundstate Li-like carbon [C 3+ (1s 2... more Absolute cross sections for the K-shell photoionization of groundstate Li-like carbon [C 3+ (1s 2 2s 2 S)] ions were measured by employing the ionphoton merged-beams technique at the Advanced Light Source. The energy ranges 299.8-300.15 eV, 303.29-303.58 eV and 335.61-337.57 eV of the [1s(2s2p) 3 P] 2 P, [1s(2s2p) 1 P] 2 P and [(1s2s) 3 S 3p] 2 P resonances, respectively, were investigated using resolving powers of up to 6000. The autoionization linewidth of the [1s(2s2p) 1 P] 2 P resonance was measured to be 27±5 meV and compares favourably with a theoretical result of 26 meV obtained from the intermediate coupling R-Matrix method. The present photoionization cross section results are compared with the outcome from photorecombination measurements by employing the principle of detailed balance.
Journal of Physics B: Atomic, Molecular and Optical Physics, 2003
Abstract We have investigated L-shell photoionization (PI) of 1S ground-state and 3Po metastable ... more Abstract We have investigated L-shell photoionization (PI) of 1S ground-state and 3Po metastable states of the Be-like ion, B+, in the photon energy range 22.4–31.3 eV, at an experimental energy resolution of 25 meV. Absolute PI cross sections have been measured using a photon–ion merged-beams arrangement at the Advanced Light Source. Detailed calculations using the semi-relativistic Breit–Pauli R-matrix approach suggest a fraction of 29% of metastable ions in the primary beam of the experiment. Excellent agreement is ...
Page 1. Doubly excited resonances in the photoionization spectrum of Li+: experiment and theory T... more Page 1. Doubly excited resonances in the photoionization spectrum of Li+: experiment and theory This article has been downloaded from IOPscience. Please scroll down to see the full text article. 2006 J. Phys. B: At. Mol. Opt. Phys. 39 3957 (http://iopscience.iop.org/0953- 4075/39/18/024) Download details: IP Address: 66.249.71.214 The article was downloaded on 09/06/2011 at 05:56 Please note that terms and conditions apply. View the table of contents for this issue, or go to the journal homepage for more ...
An evaluation has been made of the existing experimental and theoretical cross-section data for e... more An evaluation has been made of the existing experimental and theoretical cross-section data for electron capture and ionization in collisions of c4+ and Oq+ ions (1 G q d 2) with H, He, and H2. Sets of recommended cross-section data with specified accuracies are presented in the energy range of interest to controlled thermonuclear fusion research. Chebyshev polynomial fits to the recommended data are aho given. o 1988 Academic PRSS. I~C.
Page 1. Valence-shell photoionization of C-like Ar+ Ions This article has been downloaded from IO... more Page 1. Valence-shell photoionization of C-like Ar+ Ions This article has been downloaded from IOPscience. Please scroll down to see the full text article. 2012 J. Phys.: Conf. Ser. 388 022035 (http://iopscience.iop.org/1742-6596/388/2/022035) Download details: IP Address: 66.249.76.219 The article was downloaded on 06/11/2012 at 07:06 Please note that terms and conditions apply. View the table of contents for this issue, or go to the journal homepage for more Home Search Collections Journals About Contact us My IOPscience Page 2. ...
Measured cross sections for electron-impact ionization of ${\mathrm{C}}^{3+}$ and ${\mathrm{N}}^{... more Measured cross sections for electron-impact ionization of ${\mathrm{C}}^{3+}$ and ${\mathrm{N}}^{4+}$ are reported for collision energies between threshold and 500 eV. The measurements were performed with crossed electron and ion beams. The peak cross sections obtained are 2.3 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}18}$ ${\mathrm{cm}}^{2}$ near 200 eV for ${\mathrm{C}}^{3+}$ and 1.5 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}18}$ ${\mathrm{cm}}^{2}$ near 400 eV for ${\mathrm{N}}^{4+}$ with good-confidence absolute uncertainties of \ifmmode\pm\else\textpm\fi{} 11% and \ifmmode\pm\else\textpm\fi{} 15%, respectively. Comparisons of present data with the available theoretical estimates range from good agreement to discrepancies of a factor of two. At the highest energies of the present measurements, near 500 eV, the cross sections have not yet begun to decrease as predicted by all the available theories. It is postulated that inner-shell-electron excitation followed by autoionization is contributing to the measured ionization cross sections at these energies. Ionization-rate coefficients are derived from the data and compared with those measured in plasmas. The agreement in ionization rates is satisfactory in the ${\mathrm{C}}^{3+}$ case, but discrepancies of nearly a factor of two exist for the ${\mathrm{N}}^{4+}$ case.
High-resolution measurements of the photoionization cross sections of the Na-isoelectronic ions M... more High-resolution measurements of the photoionization cross sections of the Na-isoelectronic ions Mg+ and Al2+ are presented, to be compared with earlier measurements in which structure in the most prominent peaks was unresolved. These measurements have been normalized to the earlier ones in order to provide values of the oscillator strengths of the newly resolved peaks, and comparison is made with
Absolute cross sections for charge exchange, ionization, stripping and excitation in K + −He coll... more Absolute cross sections for charge exchange, ionization, stripping and excitation in K + −He collisions were measured in the ion energy range 0.7 − 10 keV. The experimental data and the schematic correlation diagrams are used to analyze and determine the mechanisms for these processes. The increase of the excitation probability of inelastic channels with the angle of scattering is revealed. An exceptionally highly excited state of He is observed and a peculiarity for the excitation function of the resonance line is explained. The intensity ratio for the excitation of the K II λ = 60.1 nm and λ = 61.2 nm lines is 5:1 which indicates the high probability for excitation of the singlet resonance level 1 P1 compared to the triplet level 3 P1. The similarity of the population of the 4p state of the potassium ion and atom as well as the anomalously small values of the excitation cross sections are explained.
Journal of Physics B: Atomic, Molecular and Optical Physics, 2016
Experimental and theoretical results are reported for single-photon single ionization of and W3+ ... more Experimental and theoretical results are reported for single-photon single ionization of and W3+ tungsten ions. Experiments were performed at the photon–ion merged-beam setup of the Advanced Light Source in Berkeley. Absolute cross sections and detailed energy scans were measured over an energy range 20–90 eV at a bandwidth of 100 meV. Broad peak features with widths typically around 5 eV have been observed with almost no narrow resonances present in the investigated energy range. Theoretical results were obtained from a Dirac–Coulomb R-matrix approach. The calculations were carried out for the lowest-energy terms of the investigated tungsten ions with levels for and for . Assuming a statistically weighted distribution of ions in the initial ground-term levels there is good agreement of theory and experiment for ions. However, for ions at higher energies there is a factor of approximately two difference between experimental and theoretical cross sections.
A crossed charged beam technique was employed in the investigation reported. The ion beam was cro... more A crossed charged beam technique was employed in the investigation reported. The ion beam was crossed at right angles by a magnetically confined electron beam. Cross sections were determined as a function of electron impact energy. Considerable structure in the excitation cross section appears immediately above the threshold. It is pointed out that a primary application of cross sections is related to the calculation of plasma rate coefficients.
Cross sections for the photoionization ͑PI͒ of Sc 2ϩ ions with ͓Ar͔3d ground-state configuration ... more Cross sections for the photoionization ͑PI͒ of Sc 2ϩ ions with ͓Ar͔3d ground-state configuration have been measured by employing the merged ion-photon beams method. The Sc 2ϩ ions were produced from metallic vapor in an electron cyclotron resonance ion source, and the photon beam was generated by an undulator in the electron-synchrotron storage ring of the advanced light source of the Lawrence Berkeley National Laboratory. The experimental photon energy range 23-68 eV encompasses the direct 3d and 3p photoionization thresholds. The experimental photoion spectrum is dominated by autoionizing resonances due to 3p excitations predominantly decaying via Coster-Kronig and super-Coster-Kronig transitions. Individual resonances located around EϷ40.2 eV have been measured with an instrumental energy spread ⌬E as low as 1.2 meV, corresponding to a resolving power of E/(⌬E) around 33 500. The fractions of metastable ions in the Sc 2ϩ ion beam are obtained by comparing the photoionization cross section with the recently measured ͓Schippers et al., Phys. Rev. A 65, 042723 ͑2002͔͒ cross section for the time-reversed process of photorecombination of Sc 3ϩ ions. Absolute strengths of several 3p 5 3d 2 and 3p 5 3d 4s PI resonances have been determined. They are the same as the corresponding resonance strengths for isoelectronic Ca ϩ ions.
Measurements of absolute total cross sections for electron capture by C[sup 3+] in collisions wit... more Measurements of absolute total cross sections for electron capture by C[sup 3+] in collisions with ground-state hydrogen and deuterium are reported in the energy range 0.3--3000 eV/u. In general, good agreement is obtained with published experimental measurements at the lower (10--110 eV/u) and higher ([gt]1 keV/u) collision energies. However, the improved accuracy and the large energy range of these measurements made possible by the merged-beams technique indicate an energy dependence different than was suggested by interpolating previous published and unpublished measurements and by a theoretical calculation that attempted to reconcile the previous low- and high-energy total-capture cross-section data. The present measurements above 100 eV/u show excellent agreement with a more recent 22-state molecular-orbital calculation that predicts slight structure in the cross section at collision energies between 1000 and 2000 eV/u. Below 100 eV/u, the present measurements, which were performed with deuterium, deviate from an energy dependence suggested by earlier hydrogen measurements and by fully quantal calculations.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1991
DE91 001214 7b quantitatively study electron capture during collisions of multiply charged ions w... more DE91 001214 7b quantitatively study electron capture during collisions of multiply charged ions wit.h neutral atoms at near-thermal energies, ke V-enerqy multicharged ion beams are rTterged with ground-state beams of H or D at.ores of chosen, velocity such. that collisions tn the relative energy range I-I000 eV/ainu result. Recent. data for 0 a4, 04+ 4-H(D) are presented and compared with, theoretical pred;_ions. Recently complet2d modificationsto the apparatus are described that will provide a significant improvement in, signal-to-background and angular collection. These improvements will allow measurements to be extended to lower energies, where effects due to the ion-induced dipole attraction may be evident, DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government, Neither the United States Government nor any agency thereof, nor any of their ptlbli.';h t_r rcl'q'_*:
Journal of Physics B: Atomic, Molecular and Optical Physics, 2012
Absolute single photoionization cross-section measurements of Se3+ and Se5+ ions were performed u... more Absolute single photoionization cross-section measurements of Se3+ and Se5+ ions were performed using monochromatized synchrotron radiation and the photo-ion merged-beams technique. Se3 + measurements were made at a photon energy resolution of 20 ± 3 meV from 41.90 to 54.56 eV, spanning the 2P1/2 ground state ionization threshold. Numerous autoionizing resonances arising from both the 2P1/2 ground state and 2P3/2 metastable state are identified using quantum defect analysis. For Se5 +, measurements were made at a photon energy resolution of 60 ± 10 meV from 81 to 101 eV, spanning the 2S1/2 ground state ionization threshold, and at a photon energy resolution of 28 ± 3 meV from 100.175 to 106.675 eV in a region rich with autoionizing resonances. The direct ionization threshold of the Se5 +2S1/2 ground state is experimentally determined to be 81.780 ± 0.010 eV.
Journal of Physics B: Atomic, Molecular and Optical Physics, 2010
Absolute cross sections for the K-shell photoionization of groundstate Li-like carbon [C 3+ (1s 2... more Absolute cross sections for the K-shell photoionization of groundstate Li-like carbon [C 3+ (1s 2 2s 2 S)] ions were measured by employing the ionphoton merged-beams technique at the Advanced Light Source. The energy ranges 299.8-300.15 eV, 303.29-303.58 eV and 335.61-337.57 eV of the [1s(2s2p) 3 P] 2 P, [1s(2s2p) 1 P] 2 P and [(1s2s) 3 S 3p] 2 P resonances, respectively, were investigated using resolving powers of up to 6000. The autoionization linewidth of the [1s(2s2p) 1 P] 2 P resonance was measured to be 27±5 meV and compares favourably with a theoretical result of 26 meV obtained from the intermediate coupling R-Matrix method. The present photoionization cross section results are compared with the outcome from photorecombination measurements by employing the principle of detailed balance.
Journal of Physics B: Atomic, Molecular and Optical Physics, 2003
Abstract We have investigated L-shell photoionization (PI) of 1S ground-state and 3Po metastable ... more Abstract We have investigated L-shell photoionization (PI) of 1S ground-state and 3Po metastable states of the Be-like ion, B+, in the photon energy range 22.4–31.3 eV, at an experimental energy resolution of 25 meV. Absolute PI cross sections have been measured using a photon–ion merged-beams arrangement at the Advanced Light Source. Detailed calculations using the semi-relativistic Breit–Pauli R-matrix approach suggest a fraction of 29% of metastable ions in the primary beam of the experiment. Excellent agreement is ...
Page 1. Doubly excited resonances in the photoionization spectrum of Li+: experiment and theory T... more Page 1. Doubly excited resonances in the photoionization spectrum of Li+: experiment and theory This article has been downloaded from IOPscience. Please scroll down to see the full text article. 2006 J. Phys. B: At. Mol. Opt. Phys. 39 3957 (http://iopscience.iop.org/0953- 4075/39/18/024) Download details: IP Address: 66.249.71.214 The article was downloaded on 09/06/2011 at 05:56 Please note that terms and conditions apply. View the table of contents for this issue, or go to the journal homepage for more ...
An evaluation has been made of the existing experimental and theoretical cross-section data for e... more An evaluation has been made of the existing experimental and theoretical cross-section data for electron capture and ionization in collisions of c4+ and Oq+ ions (1 G q d 2) with H, He, and H2. Sets of recommended cross-section data with specified accuracies are presented in the energy range of interest to controlled thermonuclear fusion research. Chebyshev polynomial fits to the recommended data are aho given. o 1988 Academic PRSS. I~C.
Page 1. Valence-shell photoionization of C-like Ar+ Ions This article has been downloaded from IO... more Page 1. Valence-shell photoionization of C-like Ar+ Ions This article has been downloaded from IOPscience. Please scroll down to see the full text article. 2012 J. Phys.: Conf. Ser. 388 022035 (http://iopscience.iop.org/1742-6596/388/2/022035) Download details: IP Address: 66.249.76.219 The article was downloaded on 06/11/2012 at 07:06 Please note that terms and conditions apply. View the table of contents for this issue, or go to the journal homepage for more Home Search Collections Journals About Contact us My IOPscience Page 2. ...
Measured cross sections for electron-impact ionization of ${\mathrm{C}}^{3+}$ and ${\mathrm{N}}^{... more Measured cross sections for electron-impact ionization of ${\mathrm{C}}^{3+}$ and ${\mathrm{N}}^{4+}$ are reported for collision energies between threshold and 500 eV. The measurements were performed with crossed electron and ion beams. The peak cross sections obtained are 2.3 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}18}$ ${\mathrm{cm}}^{2}$ near 200 eV for ${\mathrm{C}}^{3+}$ and 1.5 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}18}$ ${\mathrm{cm}}^{2}$ near 400 eV for ${\mathrm{N}}^{4+}$ with good-confidence absolute uncertainties of \ifmmode\pm\else\textpm\fi{} 11% and \ifmmode\pm\else\textpm\fi{} 15%, respectively. Comparisons of present data with the available theoretical estimates range from good agreement to discrepancies of a factor of two. At the highest energies of the present measurements, near 500 eV, the cross sections have not yet begun to decrease as predicted by all the available theories. It is postulated that inner-shell-electron excitation followed by autoionization is contributing to the measured ionization cross sections at these energies. Ionization-rate coefficients are derived from the data and compared with those measured in plasmas. The agreement in ionization rates is satisfactory in the ${\mathrm{C}}^{3+}$ case, but discrepancies of nearly a factor of two exist for the ${\mathrm{N}}^{4+}$ case.
High-resolution measurements of the photoionization cross sections of the Na-isoelectronic ions M... more High-resolution measurements of the photoionization cross sections of the Na-isoelectronic ions Mg+ and Al2+ are presented, to be compared with earlier measurements in which structure in the most prominent peaks was unresolved. These measurements have been normalized to the earlier ones in order to provide values of the oscillator strengths of the newly resolved peaks, and comparison is made with
Absolute cross sections for charge exchange, ionization, stripping and excitation in K + −He coll... more Absolute cross sections for charge exchange, ionization, stripping and excitation in K + −He collisions were measured in the ion energy range 0.7 − 10 keV. The experimental data and the schematic correlation diagrams are used to analyze and determine the mechanisms for these processes. The increase of the excitation probability of inelastic channels with the angle of scattering is revealed. An exceptionally highly excited state of He is observed and a peculiarity for the excitation function of the resonance line is explained. The intensity ratio for the excitation of the K II λ = 60.1 nm and λ = 61.2 nm lines is 5:1 which indicates the high probability for excitation of the singlet resonance level 1 P1 compared to the triplet level 3 P1. The similarity of the population of the 4p state of the potassium ion and atom as well as the anomalously small values of the excitation cross sections are explained.
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