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A. J. J. Raassen - One of the best experts on this subject based on the ideXlab platform.
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Charge Exchange in galaxy clusters
Astronomy & Astrophysics, 2018Co-Authors: Junjie Mao, Jelle De Plaa, A. J. J. Raassen, Chintan Shah, Jelle S. KaastraAbstract:Though theoretically expected, the Charge Exchange emission from galaxy clusters has not yet been confidently detected. Accumulating hints were reported recently, including a rather marginal detection with the Hitomi data of the Perseus cluster. As suggested in Gu et al. (2015), a detection of Charge Exchange line emission from galaxy clusters would not only impact the interpretation of the newly-discovered 3.5 keV line, but also open up a new research topic on the interaction between hot and cold matter in clusters. We aim to perform the most systematic search for the O VIII Charge Exchange line in cluster spectra using the RGS on board XMM. We introduce a sample of 21 clusters observed with the RGS. The dominating thermal plasma emission is modeled and subtracted with a two-temperature CIE component, and the residuals are stacked for the line search. The systematic uncertainties in the fits are quantified by refitting the spectra with a varying continuum and line broadening. By the residual stacking, we do find a hint of a line-like feature at 14.82 A, the characteristic wavelength expected for oxygen Charge Exchange. This feature has a marginal significance of 2.8 sigma, and the average equivalent width is 2.5E-4 keV. We further demonstrate that the putative feature can be hardly affected by the systematic errors from continuum modelling and instrumental effects, or the atomic uncertainties of the neighbouring thermal lines. Assuming a realistic temperature and abundance pattern, the physical model implied by the possible oxygen line agrees well with the theoretical model proposed previously to explain the reported 3.5 keV line. If the Charge Exchange source indeed exists, we would expect that the oxygen abundance is potentially overestimated by 8-22% in previous X-ray measurements which assumed pure thermal lines.
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plasma code for astrophysical Charge Exchange emission at x ray wavelengths
Astronomy and Astrophysics, 2016Co-Authors: A. J. J. Raassen, J S KaastraAbstract:Charge Exchange X-ray emission provides unique insight into the interactions between cold and hot astrophysical plasmas. Besides its own profound science, this emission is also technically crucial to all observations in the X-ray band, since Charge Exchange with the solar wind often contributes a significant foreground component that contaminates the signal of interest. By approximating the cross sections resolved to n and l atomic subshells and carrying out complete radiative cascade calculation, we have created a new spectral code to evaluate the Charge Exchange emission in the X-ray band. Compared to collisional thermal emission, Charge Exchange radiation exhibits enhanced lines from large-n shells to the ground, as well as large forbidden-to-resonance ratios of triplet transitions. Our new model successfully reproduces an observed high-quality spectrum of comet C/2000 WM1 (LINEAR), which emits purely by Charge Exchange between solar wind ions and cometary neutrals. It demonstrates that a proper Charge Exchange model will allow us to probe the ion properties remotely, including Charge state, dynamics, and composition, at the interface between the cold and hot plasmas.
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plasma code for astrophysical Charge Exchange emission at x ray wavelengths
arXiv: High Energy Astrophysical Phenomena, 2016Co-Authors: A. J. J. Raassen, J S KaastraAbstract:Charge Exchange X-ray emission provides unique insights into the interactions between cold and hot astrophysical plasmas. Besides its own profound science, this emission is also technically crucial to all observations in the X-ray band, since Charge Exchange with the solar wind often contributes a significant foreground component that contaminates the signal of interest. By approximating the cross sections resolved to $n$ and $l$ atomic subshells, and carrying out complete radiative cascade calculation, we create a new spectral code to evaluate the Charge Exchange emission in the X-ray band. Comparing to collisional thermal emission, Charge Exchange radiation exhibits enhanced lines from large-$n$ shells to the ground, as well as large forbidden-to-resonance ratios of triplet transitions. Our new model successfully reproduces an observed high-quality spectrum of comet C/2000 WM1 (LINEAR), which emits purely by Charge Exchange between solar wind ions and cometary neutrals. It demonstrates that a proper Charge Exchange model will allow us to probe remotely the ion properties, including Charge state, dynamics, and composition, at the interface between the cold and hot plasmas.
J S Kaastra - One of the best experts on this subject based on the ideXlab platform.
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plasma code for astrophysical Charge Exchange emission at x ray wavelengths
Astronomy and Astrophysics, 2016Co-Authors: A. J. J. Raassen, J S KaastraAbstract:Charge Exchange X-ray emission provides unique insight into the interactions between cold and hot astrophysical plasmas. Besides its own profound science, this emission is also technically crucial to all observations in the X-ray band, since Charge Exchange with the solar wind often contributes a significant foreground component that contaminates the signal of interest. By approximating the cross sections resolved to n and l atomic subshells and carrying out complete radiative cascade calculation, we have created a new spectral code to evaluate the Charge Exchange emission in the X-ray band. Compared to collisional thermal emission, Charge Exchange radiation exhibits enhanced lines from large-n shells to the ground, as well as large forbidden-to-resonance ratios of triplet transitions. Our new model successfully reproduces an observed high-quality spectrum of comet C/2000 WM1 (LINEAR), which emits purely by Charge Exchange between solar wind ions and cometary neutrals. It demonstrates that a proper Charge Exchange model will allow us to probe the ion properties remotely, including Charge state, dynamics, and composition, at the interface between the cold and hot plasmas.
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plasma code for astrophysical Charge Exchange emission at x ray wavelengths
arXiv: High Energy Astrophysical Phenomena, 2016Co-Authors: A. J. J. Raassen, J S KaastraAbstract:Charge Exchange X-ray emission provides unique insights into the interactions between cold and hot astrophysical plasmas. Besides its own profound science, this emission is also technically crucial to all observations in the X-ray band, since Charge Exchange with the solar wind often contributes a significant foreground component that contaminates the signal of interest. By approximating the cross sections resolved to $n$ and $l$ atomic subshells, and carrying out complete radiative cascade calculation, we create a new spectral code to evaluate the Charge Exchange emission in the X-ray band. Comparing to collisional thermal emission, Charge Exchange radiation exhibits enhanced lines from large-$n$ shells to the ground, as well as large forbidden-to-resonance ratios of triplet transitions. Our new model successfully reproduces an observed high-quality spectrum of comet C/2000 WM1 (LINEAR), which emits purely by Charge Exchange between solar wind ions and cometary neutrals. It demonstrates that a proper Charge Exchange model will allow us to probe remotely the ion properties, including Charge state, dynamics, and composition, at the interface between the cold and hot plasmas.
Alexander Dalgarno - One of the best experts on this subject based on the ideXlab platform.
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Charge Exchange in collisions of beryllium with its ion.
Physical Chemistry Chemical Physics, 2011Co-Authors: Peng Zhang, Alexander Dalgarno, Robin Côté, Enrico BodoAbstract:Close-coupling calculations of the resonance and near resonance Charge Exchange in ion–atom collisions of Be+2 at low and intermediate energies are presented. Accurate ab initio calculations are carried out of the Born–Oppenheimer potentials and the non-adiabatic couplings that are due to the finite nuclear masses and drive the near resonance Charge Exchange. We show that the near resonance Charge Exchange cross section follows Wigner's threshold law of inelastic processes for energies below 10−8 eV and that the zero temperature rate constant for it is 4.5 × 10−10 cm3 s−1. At collision energies much larger than the isotope shift of the ionization potentials of the atoms, we show that the near resonance Charge Exchange process is equivalent to the resonance Charge Exchange with cross sections having a logarithmic dependence. We also investigate the perturbation to the Charge Exchange process due to the non-adiabatic interaction to an electronic excited state. We show that the influence is negligible at low temperatures and still small at intermediate energies despite the presence of resonances.
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near resonance Charge Exchange in ion atom collisions of lithium isotopes
Journal of Physical Chemistry A, 2009Co-Authors: Peng Zhang, Enrico Bodo, Alexander DalgarnoAbstract:Collisions of ions and atoms of 6Li and 7Li are explored theoretically over a wide range of energy from 10−14 to 1 eV. Accurate ab initio calculations are carried out of the Born−Oppenheimer potentials and the nonadiabatic couplings that are responsible for the near resonance Charge Exchange. Scattering studies show that the calculated Charge Exchange cross section follows Wigner’s law for inelastic processes for energies below 10−10 eV and that the zero temperature rate constant for it is 2.1 × 10−9 cm3 s−1. At collision energies much larger than the isotope shift of the ionization potentials of the atoms, we show that the near resonance Charge Exchange process is equivalent to the resonance Charge Exchange with cross sections having a logarithmic dependence on energy. A comparison with the Langevin model at intermediate energies is also presented.
Peng Zhang - One of the best experts on this subject based on the ideXlab platform.
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Charge Exchange in collisions of beryllium with its ion.
Physical Chemistry Chemical Physics, 2011Co-Authors: Peng Zhang, Alexander Dalgarno, Robin Côté, Enrico BodoAbstract:Close-coupling calculations of the resonance and near resonance Charge Exchange in ion–atom collisions of Be+2 at low and intermediate energies are presented. Accurate ab initio calculations are carried out of the Born–Oppenheimer potentials and the non-adiabatic couplings that are due to the finite nuclear masses and drive the near resonance Charge Exchange. We show that the near resonance Charge Exchange cross section follows Wigner's threshold law of inelastic processes for energies below 10−8 eV and that the zero temperature rate constant for it is 4.5 × 10−10 cm3 s−1. At collision energies much larger than the isotope shift of the ionization potentials of the atoms, we show that the near resonance Charge Exchange process is equivalent to the resonance Charge Exchange with cross sections having a logarithmic dependence. We also investigate the perturbation to the Charge Exchange process due to the non-adiabatic interaction to an electronic excited state. We show that the influence is negligible at low temperatures and still small at intermediate energies despite the presence of resonances.
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near resonance Charge Exchange in ion atom collisions of lithium isotopes
Journal of Physical Chemistry A, 2009Co-Authors: Peng Zhang, Enrico Bodo, Alexander DalgarnoAbstract:Collisions of ions and atoms of 6Li and 7Li are explored theoretically over a wide range of energy from 10−14 to 1 eV. Accurate ab initio calculations are carried out of the Born−Oppenheimer potentials and the nonadiabatic couplings that are responsible for the near resonance Charge Exchange. Scattering studies show that the calculated Charge Exchange cross section follows Wigner’s law for inelastic processes for energies below 10−10 eV and that the zero temperature rate constant for it is 2.1 × 10−9 cm3 s−1. At collision energies much larger than the isotope shift of the ionization potentials of the atoms, we show that the near resonance Charge Exchange process is equivalent to the resonance Charge Exchange with cross sections having a logarithmic dependence on energy. A comparison with the Langevin model at intermediate energies is also presented.
Enrico Bodo - One of the best experts on this subject based on the ideXlab platform.
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Charge Exchange in collisions of beryllium with its ion.
Physical Chemistry Chemical Physics, 2011Co-Authors: Peng Zhang, Alexander Dalgarno, Robin Côté, Enrico BodoAbstract:Close-coupling calculations of the resonance and near resonance Charge Exchange in ion–atom collisions of Be+2 at low and intermediate energies are presented. Accurate ab initio calculations are carried out of the Born–Oppenheimer potentials and the non-adiabatic couplings that are due to the finite nuclear masses and drive the near resonance Charge Exchange. We show that the near resonance Charge Exchange cross section follows Wigner's threshold law of inelastic processes for energies below 10−8 eV and that the zero temperature rate constant for it is 4.5 × 10−10 cm3 s−1. At collision energies much larger than the isotope shift of the ionization potentials of the atoms, we show that the near resonance Charge Exchange process is equivalent to the resonance Charge Exchange with cross sections having a logarithmic dependence. We also investigate the perturbation to the Charge Exchange process due to the non-adiabatic interaction to an electronic excited state. We show that the influence is negligible at low temperatures and still small at intermediate energies despite the presence of resonances.
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near resonance Charge Exchange in ion atom collisions of lithium isotopes
Journal of Physical Chemistry A, 2009Co-Authors: Peng Zhang, Enrico Bodo, Alexander DalgarnoAbstract:Collisions of ions and atoms of 6Li and 7Li are explored theoretically over a wide range of energy from 10−14 to 1 eV. Accurate ab initio calculations are carried out of the Born−Oppenheimer potentials and the nonadiabatic couplings that are responsible for the near resonance Charge Exchange. Scattering studies show that the calculated Charge Exchange cross section follows Wigner’s law for inelastic processes for energies below 10−10 eV and that the zero temperature rate constant for it is 2.1 × 10−9 cm3 s−1. At collision energies much larger than the isotope shift of the ionization potentials of the atoms, we show that the near resonance Charge Exchange process is equivalent to the resonance Charge Exchange with cross sections having a logarithmic dependence on energy. A comparison with the Langevin model at intermediate energies is also presented.