anisotropic dielectronic resonances from magnetic-dipole lines
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Anisotropic dielectronic resonancesfrom magnetic-dipole lines
Yuri Ralchenko
National Institute ofStandards and TechnologyGaithersburg, MD, USA
ADAS Workshop, 2013Supported in part by the Office of Fusion Energy Sciences, U.S. DoE
Analyzing 10,000-eV dielectronic resonanceswith 80-eV forbidden lines
Yuri Ralchenko
National Institute ofStandards and TechnologyGaithersburg, MD, USA
ADAS Workshop, 2013Supported in part by the Office of Fusion Energy Sciences, U.S. DoE
Yu. Ralchenko & J.D. GillaspyPhysical Review A 88, 012506 (2013)
Radiative recombination
Continuum
Bound states
๐ด( ๐+1 )+ยฟ+๐โ ๐ด๐ +ยฟ+h๐ ยฟยฟ
Ion recombined
DR step 1: dielectronic capture
Continuum
Bound states
Resonant process!
๐ด( ๐+1 )+ยฟ+๐ โ ๐ด๐ +โโยฟ
Continuum
Bound states
Dielectronic capture + autoionization= no recombination
DC and AI aredirect and inverse
DR step 2: radiative stabilization
Continuum
Bound states
๐ด( ๐+1 )+ยฟ+๐ โ ๐ด๐ +โโ โ ๐ด๐ +โ+h๐ยฟ
Stabilizing transition:Mostly x-rays
Dielectronic recombination in plasmas
Z
Z+1โฆ
Maxwellian
Electrons are presentat all energies
(Infinite) Series of transitions areto be accounted for
DR
DR measurements on EBITsEBIT electron
beam
extractedions
Is ionization distribution the sameinside and outside the trap?..
NO!
1. Extract ions2. Measure ionization distribution
Beam energy
time
ER
ER
ER
Fast beam ramping
DR energy generally does not coincide with the energy of max abundance
DR resonances with M-shell (n=3) ions
LMN resonances:L electron into M,free electron into N
1s22s22p63s23p63dn
Calculation of LMn DR strength: Ca-like 3d2 W54+
2s1/2 3d2p1/2 3d2p3/2 3d
e 3de 4le 5l
1s2(2s2p)83s23p63d + e 1s2(2s2p)73s23p63d2nl
Relativistic model potential+ QED corrections(Flexible Atomic Code, Gu 2008)
Strategy1. Scan electron beam
energy with a small step (a few eV)
2. When a beam hits a DR, ionization balance changes
3. Both the populations of all levels within an ion and the corresponding line intensities change as well
4. Measure line intensity ratios from neighbor ions and look for resonances
5. EUV lines: forbidden magnetic-dipole lines within the ground configuration
A(E1) ~ 1015 s-1
A(M1) ~ 105-106 s-1
I = NAE (intensity)
Ionization potential
Ca-like W54+
Beam energy: 0.1 keV โ 30 keVBeam resolution: ~50 eVBeam current: โค 150 mABeam radius: ~30 ฮผmElectron density: ~1012 cm-3
Can produce > 60-timesionized atoms
Ar, Kr, Xe, Sn, Ti, Sm, Gd, Dy,Er, Hf, Ta, W, Pt, Au, Bi,โฆ
NIST Electron Beam Ion Trap1.0
0.8
0.6
0.4
0.2
0.0
Nor
mal
ized
Cro
ss S
ectio
n
140120100806040200
Speed [106
m/s]
EBIT Electron Beam (width x10) Maxwell-Boltzmann distribution
8 keV
x10
Monoenergetic beam allows one to โtouchโ dielectronic resonances
Yu. Ralchenko et al, Phys. Rev. A 83, 032517 (2011)
Almost all lines are M1Good statisticsIsolated lines
Pair of lines:(a) within 3d in K-like W55+ (b) within 3d2 in Ca-like W54+
EUV spectrum of W47+-W56+: M1 lines within 3dn ground configurations
[Ca]/[K]๐ 54+ยฟ3 ๐2
๐ฝ =2 โ3๐ 2๐ฝ=3
๐ 5 5+ยฟ3 ๐3/ 2 โ3๐5 /2 ยฟยฟ
[Ca]/[K]:๐ 54+ยฟ3 ๐2
๐ฝ =2 โ3๐ 2๐ฝ=3
๐ 5 5+ยฟ3 ๐3/ 2 โ3๐5 /2 ยฟยฟ
THEORY:no DR
Modeling: CR code NOMAD, atomic data from FAC
[Ca]/[K]๐ 54+ยฟ3 ๐2
๐ฝ =2 โ3๐ 2๐ฝ=3
๐ 5 5+ยฟ3 ๐3/ 2 โ3๐5 /2 ยฟยฟ
THEORY:no DR
[Ca]/[K]๐ 54+ยฟ3 ๐2
๐ฝ =2 โ3๐ 2๐ฝ=3
๐ 5 5+ยฟ3 ๐3/ 2 โ3๐5 /2 ยฟยฟ
THEORY:no DRisotropic DR
Non-Maxwellian (40-eV Gaussian) collisional-radiative model: ~10,500 levels
[Ca]/[K]๐ 54+ยฟ3 ๐2
๐ฝ =2 โ3๐ 2๐ฝ=3
๐ 5 5+ยฟ3 ๐3/ 2 โ3๐5 /2 ยฟยฟ
THEORY:no DRisotropic DRanisotropic DR
atomic level degenerate
magneticsublevels
Jm=-J
m=+J
Impact beam electrons are monodirectional
Non-Maxwellian (40-eV Gaussian) collisional-radiative model: ~10,500 levels
[Ca]/[K]๐ 54+ยฟ3 ๐2
๐ฝ =2 โ3๐ 2๐ฝ=3
๐ 5 5+ยฟ3 ๐3/ 2 โ3๐5 /2 ยฟยฟ
THEORY:no DRisotropic DRanisotropic DR
atomic level degenerate
magneticsublevels
Jm=-J
m=+J
Impact beam electrons are monodirectional
Non-Maxwellian (40-eV Gaussian) collisional-radiative model: ~18,500 levels
[Ca]/[K]๐ 54+ยฟ3 ๐2
๐ฝ =2 โ3๐ 2๐ฝ=3
๐ 5 5+ยฟ3 ๐3/ 2 โ3๐5 /2 ยฟยฟ
2p3/2 3de 4l
One EBIT run, several ionsโฆ
Can=4 Sc Ti
Where are the 10-keV photons?..
2p53s23p63dn+14l
2s1/22p1/2
2p3/2
3s 3p3d
4s 4p 4d 4f
~8keV~9keV
~11keV
X-ray emission (Ge detector)
2p53/2-4l
2p53/2-3d
2p53/2-3s
B and C: horizontal
A: slant
n>0 transitions into the 2p3/2 hole
ConclusionsโขA new in situ method to measure multi-
keV dielectronic resonances in 3dn ions using ratios of EUV magnetic-dipole lines
โขFirst resolved measurements of LMN resonances in ~55-times ionized W
โขCR modeling shows importance of anisotropic effects on ionization balance
โขIsolated resonances allow determination of the beam width
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