H- and He-like X-ray emission due to charge exchange

Transcription

1 H- and He-like X-ray emission due to charge exchange RENATA CUMBEE NPP FELLOW (GFSC, ROB PETRE) PREVIOUSLY UNDER THE DIRECTION OF P. C. S TA N C I L

2 Outline Charge exchange (CX): The basics Why do we care? (CX in astrophysics) Producing a CX theoretical spectrum: Cross sections Radiative Cascade Theoretical Spectra Interesting features: Energy & Neutral target How do we trust the theory? Benchmarking to experiments CX Model Applications Summary

3 Charge Exchange Process ν Neutral Neutral Gas Ionized Plasma Ion

4 Charge Exchange Process ν

5 Charge Exchange Process ν

6 Charge Exchange Process

7 Charge Exchange Process ν 3 ν 2

8 Charge Exchange Process

9 Charge Exchange Process While single electron capture is significant for H-like and He-like system, multi electron capture (2 or more electrons are transferred) can be important for collision systems with more than one electron.

10 Astrophysical environments for CX Comae of comets (Bodewits et al. 2007, Mullen et al. 2017) Planetary atmospheres (Dennerl et al. 2006, Bhardwaj et al. 2007, +) Earth s exosphere (Freyberg 1998, Snowden et al. 2004) Heliosphere (Cravens 2000, Cravens et al. 2001) à contribution to diffuse soft X-ray background (Wargelin et al. 2004, Koutroumpa et al. 2009, Slavin et al. 2013, Galeazzi et al. 2014) Filaments in Perseus cluster? (Walker et al. 2015, Gu et al 2017) 3.5 kev line? (Gu et al. 2015) Rim of supernova remnants? (Katsuda et al. 2011, Cumbee et al. 2014) Starburst galaxies? (Zhang et al. 2014)

11 From Lisse et al. (1996). From Dennerl, 2002 First X-ray image of Mars Comet Hyakutake M82 From Cravens 2002 From Liu et al. 2012

12 CX Emission vs Thermal Emission X-ray emission from charge exchange produces a very distinct spectrum compared to thermal emission. With high resolution spectra, it is plausible to disentangle CX from thermal emission! Relative Intensity (arb. units) O,% + H O -% + H % f Kα r i Charge Exchange Thermal Relative Intensity (arb units) Ly δ Ne #$% + H Ne *% + H % Ly γ Ly β Charge Exchange Thermal Ly α Wavelength (Å) Wavelength (Å) 1s 1 S 3p 1 P 3s 1 S kβ 2s 1 S r Kα 2p 1 P i f 3d 1 D 2p 3 P 2s 3 S

13 Charge Exchange Theory Two steps are required to produce charge exchange X-ray emission spectrum: 1)Calculate cross-section (Not easy!) 2)Radiative cascade (easier!)

14 Charge Exchange Cross Section (σ) The probability of an electron to transfer from the neutral atom into a specific excited state (n, l, S) of the ion. Nolte, 2012 For charge exchange calculations: σ depends on the n (principle quantum number) l (orbital angular momentum quantum number S (spin quantum number) ν (collision velocity) σ nls (ν) is required to produce reliable theoretical CX X-ray emission spectra Effective area" that quantifies the likelihood of a scattering event to occur

15 Ne H Ne 9+ +H + Cross Sections n,l n,l Accuracy & difficulty Recommended Cross-sections for the n=6 quantum levels Multi-channel Landau-Zener Statistical l-distribution Low energy l-distribution Classical Trajectory Monte Carlo Atomic Orbital Close Coupling Quantum Mechanical Molecular orbital Close Coupling All available cross-sections for H- like and He-like CX collisions are implemented in Kronos Database Cumbee et al. 2016

16 Radiative Cascade 5s 5p 5d 5f 5g To produce theoretical CX X-ray emission spectra, these n and l levels are given an initial population that is directly proportional to the cross-section σ nl for that given state. i. e. Population 2s σ 2s The electron then transitions to a lower energy level, obeying quantum mechanical selection rules, l = ±1, until it reaches the ground state Photons are emitted 1s 4s 3s 3p 3d 2s 4p 4d 4f 2p cascades of transitions E Einstein A coefficient

17 Radiative Cascade Relative Intensity (arb. units) kev/u (435 km/s) MCLZ Low-energy l-distribution Ly γ σ 5s σ 5p 5d 5f 5g 4s 4p 4d 4f 3s 3p 3d 2s 2p Photon Energy (ev) 2p 1s > 3p - 1s & 4p 1s cascades of transitions 1s

18 Radiative Cascade 1 Relative Intensity (arb. units) kev/u (435 km/s) MCLZ Low-energy l-distribution Ly β 5s 4s 3s 2s 5p 5d 5f 5g 4p 4d 4f 3p 3d 2p Photon Energy (ev) 2p 1s > 3p - 1s & 4p 1s cascades of transitions 1s

19 Radiative Cascade 1 Relative Intensity (arb. units) Ly α 1 kev/u (435 km/s) MCLZ Low-energy l-distribution 5s 4s 3s 2s 5p 5d 5f 5g 4p 4d 4f 3p 3d 2p Photon Energy (ev) 2p 1s > 3p - 1s & 4p 1s The 2p-1s transition is dominant due to the cascade from higher excited states (3s, 3d, 4s, 4d, 4f). 1s cascades of transitions

20 Radiative Cascade 1 Relative Intensity (arb. units) Ly α 1 kev/u (435 km/s) MCLZ Low-energy l-distribution Ly γ Ly β 5s 5p 5d 5f 5g 4s 4p 4d 4f 3s 3p 3d 2s 2p Photon Energy (ev) 2p 1s > 3p - 1s & 4p 1s The 2p-1s transition is dominant due to the cascade from higher excited states (3s, 3d, 4s, 4d, 4f). 1s cascades of transitions

21 Outline Charge exchange (CX): The basics Why do we care? (CX in astrophysics) Producing a CX theoretical spectrum: Cross sections Radiative Cascade Theoretical Spectra Interesting features: Energy & Neutral target How do we trust the theory? Benchmarking to experiments CX Model Applications Summary

22 CX as a diagnostic CX is highly dependent on: Ion stage (O 8+, O 7+ ) Neutral target (H, He, CO 2 ) Velocity of the collision Relative Intensity (arb units) Ly α O 8+ CX 1000 ev/u collision energy MCLZ method, 10 ev FWHM Ly β Ly γ Ly δ CO H 2 O Photon Energy (ev) He N 2 CO 2 H 2 H

23 CX as a diagnostic CX is highly dependent on: Ion stage (O 8+, O 7+ ) Neutral target (H, He, CO 2 ) Velocity of the collision EBIT: Electron beam ion trap (experiment) at LLNL Relative Intensity (arb units) Ly α Mg 12+ CX at 1 ev/u EBIT (Betancourt-Martinez, 2014) MCLZ He CO 2 H 2 H Ly β Ly γ ~10 ev/u Ly δ Ly ε Ly ζ Photon Energy (ev)

24 CX as a diagnostic CX is highly dependent on: Ion stage (O 8+, O 7+ ) Neutral target (H, He, CO 2 ) Velocity of the collision EBIT: Electron beam ion trap (experiment) at LLNL Relative Intensity (arb. units) Ly ε Ly δ Ly γ Ly β 170 km/s (150 ev/u) 217 km/s (250 ev/u) 311 km/s (500 ev/u) 434 km/s (1000 ev/u) 1379 km/s (10,000 ev/u) H He (Neutral) Wavelength (Å) Ly α

25 CX as a diagnostic: Ionization stage CX is highly dependent on: Ion stage (O 8+, O 7+ ) Neutral target (H, He, CO 2 ) Velocity of the collision Relative Intensity (arb. units) Ne 9+ + H kα i f r Ne H Lyα Statistical l-distribution Low energy l-distribution MCLZ MCLZ 1 kev/u collisional energy 10 ev Gaussian FWHM Lyβ Lyγ Lyδ Lyε 0 kβ Photon Energy (ev) kγ kε

26 CX as a diagnostic: Hardness Ratios (H 2 ) CX is highly dependent on: Ion stage (O 8+, O 7+ ) Neutral target (H, He, CO 2 ) Velocity of the collision X-ray hardness ratio MCLZ (low-energy l-distribution) MCLZ SL! CTMC EBIT MCLZ (low-energy, N 2, 100 ev/u) MCLZ (SL1, N 2, 100 ev/u) 0.75 H = Ly E + Ly F + Ly H Atomic number Z A. Miller, In Prep

27 Benchmarking Theory to Experiments abc Ali et al Ne He Ne 9+ +He KeV/u Cumbee et al C 6+ +He C 5+ +He + Defayet al. (2013) C 6 + +H 2 C 5 + +H + 2 Fogle et al. (2014) Cumbee et al. 2017, accepted

28 Outline Charge exchange (CX): The basics Why do we care? (CX in astrophysics) Producing a CX theoretical spectrum: Cross sections Radiative Cascade Theoretical Spectra Interesting features: Energy & Neutral target How do we trust the theory? Benchmarking to experiments CX Model Applications Summary

29 Pure Charge exchange Model: 8 collision velocities Collision Energy: 200 ev/u Methods: QMOCC CTMC AOCC MCLZ Neutrals: H He(10%) Each spectrum is normalized to a relative intensity of 1 *relative abundance not considered

30 Pure Charge exchange Model: 8 collision velocities Collision Energy: 300 ev/u Methods: QMOCC CTMC AOCC MCLZ Neutrals: H He(10%) Each spectrum is normalized to a relative intensity of 1 *relative abundance not considered

31 Pure Charge exchange Model: 8 collision velocities Collision Energy: 500 ev/u Methods: QMOCC CTMC AOCC MCLZ Neutrals: H He(10%) Each spectrum is normalized to a relative intensity of 1 *relative abundance not considered

32 Pure Charge exchange Model: 8 collision velocities Collision Energy: 700 ev/u Methods: QMOCC CTMC AOCC MCLZ Neutrals: H He(10%) Each spectrum is normalized to a relative intensity of 1 *relative abundance not considered

33 Pure Charge exchange Model: 8 collision velocities Collision Energy: 1000 ev/u Methods: QMOCC CTMC AOCC MCLZ Neutrals: H He(10%) Each spectrum is normalized to a relative intensity of 1 *relative abundance not considered

34 Pure Charge exchange Model: 8 collision velocities Collision Energy: 2000 ev/u Methods: QMOCC CTMC AOCC MCLZ Neutrals: H He(10%) Each spectrum is normalized to a relative intensity of 1 *relative abundance not considered

35 Pure Charge exchange Model: 8 collision velocities Collision Energy: 3000 ev/u Methods: QMOCC CTMC AOCC MCLZ Neutrals: H He(10%) Each spectrum is normalized to a relative intensity of 1 *relative abundance not considered

36 Pure Charge exchange Model: 8 collision velocities Collision Energy: 5000 ev/u Methods: QMOCC CTMC AOCC MCLZ Neutrals: H He(10%) Each spectrum is normalized to a relative intensity of 1 *relative abundance not considered

37 Charge exchange Model: Cygnus Loop Supernova Remnant Counts sec 1 kev 1 (data model)/error χ 2 Counts s -1 kev XSPEC model of CX in Cygnus Loop 0.5 Photon Energy (kev) Back Illuminated 1 Front illuminated Relative Intensity (arb. units) CX contribution in XSPEC model 200 ev/u 300 ev/u 500 ev/u 700 ev/u 1000 ev/u 2000 ev/u 3000 ev/u 5000 ev/u Χ 2 ~ Photon Energy (ev)

38 CX Modeling AtomDB CX ACX2.0 M82 Zhang et al Lnie Ratio Direct Comparisons Liu et al XMM-Newton RGS Comet 10 SPEX Mullen et al., 2016 Lnie Ratio Modeling (data model)/error Counts sec 1 kev χ 2 Counts s -1 kev Energy (kev) Photon Energy (kev) 1

39 Limitations In comets, more ionization stages (other than H-like and He-like) are significant Multi-electron capture, in which 2 or more electrons is transferred can be significant for collisions with neutrals with more than 1 electron Current theory needs to be benchmarked to experiment for a variety of collision energies MCLZ is relatively easy to calculate, but requires more approximations than QMOCC or AOCC.

40 Summary Cross-sections are calculated for various ion-atom collisions H-like and He-like C, N, O, Ne, Mg, Al, and Si H and He targets km/s QMOCC, AOCC, CTMC, and MCLZ methods CX model is applied to a region on the Northeast rim of the Cygnus Loop Supernova remnant Including all ions calculated and a fraction of 10% He For 8 energies For a proper solar wind model More ionization stages (O 6+, etc) In the works All data available in Kronos Database Google search: UGA Stancil Kronos Zach Dorsey: Li-like CX Liyi Gu : Astrophysical CX Jason Terry: Double Electron Capture Ruitan Zhang: Fully stripped ions Mike Fogle: COLTRIMS measurements

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