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Assessing atomic data accuracy along isoelectronic Assessing atomic data accuracy along isoelectronic

Assessing atomic data accuracy along isoelectronic - PowerPoint Presentation

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Assessing atomic data accuracy along isoelectronic - PPT Presentation

sequences Peter Young George Mason University VA Uri Feldman Artep Inc MD Work funded by NSF and NASA The CHIANTI atomic database Atomic data and software package for modeling ID: 211214

http org young peter org http peter young pyoung aas2014 talks gmu data level atomic ions levels slide extra

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Slide1

Assessing atomic data accuracy along isoelectronic sequences

Peter Young*George Mason University, VAUri FeldmanArtep Inc, MD

*Work funded by NSF and NASASlide2

The CHIANTI atomic databaseAtomic data and software package for modeling emission linesions and neutrals for elements up to zincsoftware written in IDL and PythonFirst released in 1996 (Dere

et al. 1997, A&AS)Latest version: 7.1 (Landi et al. 2013, ApJ)Citations: 1943Large effort gone into benchmarking atomic data against observationsCHIANTI 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 YoungSlide3

The CHIANTI atomic databaseCHIANTI contains atomic data for solving level balance equations for atoms and ionsPrincipal data-sets are:electron excitation rates

radiative decay ratesexperimental energy levelsDr Peter Young (GMU)http://pyoung.org/talks/aas20143Slide4

Level populationsLevel balance equations are αji are atomic rate coefficients (radiative decay rates, electron excitation rates, etc.)n

j are the level populations (normalized so that Σ nj = 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

-3Slide5

Li-like ionsExample of a ‘good’ caseDr Peter Young (GMU)http://pyoung.org/talks/aas2014

5Slide6

He-like ionsAn atomic data error clearly seen for N VIDr Peter Young (GMU)http://pyoung.org/talks/aas2014

62-photon transition had been incorrectly assignedFixed with recent v7.1.4 releaseSlide7

C-like ions: the “iron bump”For 2p3 levels an apparent anomaly for iron is seenDr Peter Young (GMU)http://pyoung.org/talks/aas2014

7Slide8

High-Z ions vs. low-Z ionsThe excited ground configuration levels of high-Z ions gain significant population only at high densitiesConsider 2s2p3 3P0 (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

n

i

q

i,10

n

i

q

i,10

n

i

q

i,10

n

i

q

i,10

3

P

0

0.10

6.9(-12)

6.9(-13)

1.0

6.9(-13)

6.9(-13)

3

P

1

0.31

5.9(-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

-3Slide9

Fe XXI 2s 2p3 3P0Why is the population for Fe XXI 2s 2p3 3P0 enhanced?

Fe XXI has 621 levels; Mn XX has 20 levelsDr Peter Young (GMU)http://pyoung.org/talks/aas20149Mn

XX

Fe XXI

Contrib.

Level

Process

Contrib.

Level

Process

56.8%

1

e exc.

49.2%

1

e exc.

42.8%

2

e

exc.

26.0%

25

cascade

4.9%

2

e exc.

3.9%

26

cascade

The ground level excitation rate is much higher for Fe XXISlide10

Collision strength comparisonBig difference in collision strengths for weak ground level excitationDr Peter Young (GMU)http://pyoung.org/talks/aas2014

10Mn XX: Zhang & Sampson (1996, ADNDT, 63, 275) – distorted waveFe XXI: Badnell & Griffin (2001, J.Phys.B, 34, 681) – R-matrix

Iron bump caused by

enhanced direct excitation rates

cascading from high levelsSlide11

ImplementationWith CHIANTI 8 (coming soon!) we will distribute an IDL routine to plot isoelectronic level populationsFor investigating population processes of a specific level, use

Dr Peter Young (GMU)http://pyoung.org/talks/aas201411IDL> 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

level

Out of level

Radiative

decay

0.5 %

100.0

%

Electron excitation

99.5 %

0.0 %

already in CHIANTISlide12

SummaryStudying 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/aas201412See online talk for He- to Na-like sequences(http://pyoung.org/talks/aas2014)Slide13

C-like 2p4 levelsMinor elements show large differences (e.g., P X vs. S XI)Dr Peter Young (GMU)http://pyoung.org/talks/aas2014

13Slide14

P X & S XI: 2p4 1S0 levelFactor 10 difference in level population for 2p4 1S0

level – why?Error for P X oscillator strengthDr Peter Young (GMU)http://pyoung.org/talks/aas201414Transition

Zhang & Sampson

(1996)

CHIANTI

2s 2p

3

1

P

1

- 2p

4

1

S

0

0.388

3.49

The Z&S data have been replaced for the abundant elements, but not the minor elementsSlide15

Extra slide: Be-like dataDr Peter Young (GMU)http://pyoung.org/talks/aas2014

15Slide16

Extra slide: B-like dataDr Peter Young (GMU)http://pyoung.org/talks/aas2014

16Slide17

Extra slide: N-like dataDr Peter Young (GMU)http://pyoung.org/talks/aas2014

17Slide18

Extra slide: O-like dataDr Peter Young (GMU)http://pyoung.org/talks/aas2014

18Slide19

Extra slide: F-like dataDr Peter Young (GMU)http://pyoung.org/talks/aas2014

19Slide20

Extra slide: Ne-like dataDr Peter Young (GMU)http://pyoung.org/talks/aas2014

20Slide21

Extra slide: Na-like dataDr Peter Young (GMU)http://pyoung.org/talks/aas2014

21