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Peter Young* George Mason University, VA Uri Feldman Artep Inc, MD *Work funded by NSF and NASA.

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Presentation on theme: "Peter Young* George Mason University, VA Uri Feldman Artep Inc, MD *Work funded by NSF and NASA."— Presentation transcript:

1 Peter Young* George Mason University, VA Uri Feldman Artep Inc, MD *Work funded by NSF and NASA

2 Atomic data and software package for modeling emission lines – ions and neutrals for elements up to zinc – software written in IDL and Python First released in 1996 (Dere et al. 1997, A&AS) Latest version: 7.1 (Landi et al. 2013, ApJ) Citations: 1943 Large effort gone into benchmarking atomic data against observations CHIANTI atomic data are used in other codes (CLOUDY, APED, MOCASSIN, XSTAR) Dr Peter Young (GMU)http://pyoung.org/talks/aas20142 http://chiantidatabase.org Team members Ken Dere Giulio Del Zanna Enrico Landi Helen Mason Peter Young

3 CHIANTI contains atomic data for solving level balance equations for atoms and ions Principal data-sets are: – electron excitation rates – radiative decay rates – experimental energy levels Dr Peter Young (GMU)http://pyoung.org/talks/aas20143

4 Level balance equations are α ji are atomic rate coefficients (radiative decay rates, electron excitation rates, etc.) n j are the level populations (normalized so that Σ n j = 1) Dr Peter Young (GMU)http://pyoung.org/talks/aas20144 n j computed with CHIANTI IDL routines pop_solver.pro & show_pops.pro Method is to plot the n j along an isoelectronic sequence -Set temperature to be T max of ion -Use density 10 10 cm -3

5 Example of a ‘good’ case Dr Peter Young (GMU)http://pyoung.org/talks/aas20145

6 An atomic data error clearly seen for N VI Dr Peter Young (GMU)http://pyoung.org/talks/aas20146 2-photon transition had been incorrectly assigned Fixed with recent v7.1.4 release

7 For 2p 3 levels an apparent anomaly for iron is seen Dr Peter Young (GMU)http://pyoung.org/talks/aas20147

8 The excited ground configuration levels of high-Z ions gain significant population only at high densities Consider 2s2p 3 3 P 0 (index=10) level of C-like ions Dr Peter Young (GMU)http://pyoung.org/talks/aas20148 => High-Z ion models are much more sensitive to the accuracy of weak transitions Si IX (log T = 6.0)Fe XXI (log T = 7.1) Level nini q i,10 n i q i,10 nini q i,10 n i q i,10 3P03P0 0.106.9(-12)6.9(-13)1.06.9(-13) 3P13P1 0.315.9(-10)1.8(-10)9.2(-4)8.0(-11)7.4(-14) Weak 3 P 0 – 3 P 0 transition is dominant excitation channel Density=10 10 cm -3

9 Why is the population for Fe XXI 2s 2p 3 3 P 0 enhanced? Fe XXI has 621 levels; Mn XX has 20 levels Dr Peter Young (GMU)http://pyoung.org/talks/aas20149 Mn XXFe XXI Contrib.LevelProcessContrib.LevelProcess 56.8%1e exc.49.2%1e exc. 42.8%2e exc.26.0%25cascade 4.9%2e exc. 3.9%26cascade The ground level excitation rate is much higher for Fe XXI

10 Big difference in collision strengths for weak ground level excitation Dr Peter Young (GMU)http://pyoung.org/talks/aas201410 Mn XX: Zhang & Sampson (1996, ADNDT, 63, 275) – distorted wave Fe XXI: Badnell & Griffin (2001, J.Phys.B, 34, 681) – R-matrix Iron bump caused by 1.enhanced direct excitation rates 2.cascading from high levels

11 With CHIANTI 8 (coming soon!) we will distribute an IDL routine to plot isoelectronic level populations For investigating population processes of a specific level, use Dr Peter Young (GMU)http://pyoung.org/talks/aas201411 IDL> ch_plot_iso_pops, ‘o_6’, 3 (plots isoelectronic populations for the level identified as no. 3 for O VI -> 1s 2 2p 2 P 3/2 ) IDL> pop_processes, ‘o_6’, lev=3, /verbose Into levelOut of level Radiative decay0.5 %100.0 % Electron excitation99.5 %0.0 % already in CHIANTI

12 Studying level populations along isoelectronic sequences is a good way of assessing atomic data accuracy. The method focuses attention on those atomic data that most influence the populations (and hence emissivities) of the ions. For Z ≥ 20 large atomic models are critical for modeling weak ground-level excitations. Software will be distributed with CHIANTI 8. Dr Peter Young (GMU)http://pyoung.org/talks/aas201412 See online talk for He- to Na-like sequences (http://pyoung.org/talks/aas2014)

13 Minor elements show large differences (e.g., P X vs. S XI) Dr Peter Young (GMU)http://pyoung.org/talks/aas201413

14 Factor 10 difference in level population for 2p 4 1 S 0 level – why? Error for P X oscillator strength Dr Peter Young (GMU)http://pyoung.org/talks/aas201414 TransitionZhang & Sampson (1996)CHIANTI 2s 2p 3 1 P 1 - 2p 4 1 S 0 0.3883.49 The Z&S data have been replaced for the abundant elements, but not the minor elements

15 Dr Peter Young (GMU)http://pyoung.org/talks/aas201415

16 Dr Peter Young (GMU)http://pyoung.org/talks/aas201416

17 Dr Peter Young (GMU)http://pyoung.org/talks/aas201417

18 Dr Peter Young (GMU)http://pyoung.org/talks/aas201418

19 Dr Peter Young (GMU)http://pyoung.org/talks/aas201419

20 Dr Peter Young (GMU)http://pyoung.org/talks/aas201420

21 Dr Peter Young (GMU)http://pyoung.org/talks/aas201421

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