Electron-driven resonant processes Recom bination processes e beam - - PowerPoint PPT Presentation

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Electron-driven resonant processes Recom bination processes e beam - - PowerPoint PPT Presentation

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Electron-driven resonant processes Recom bination processes e beam Dielectronic recombination DR resonant two-step process: capture of a free electron and bound t n= electron excitation. E 1 radiative stabilization via photon

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Electron-driven resonant processes

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Dielectronic recombination DR

resonant two-step process:

  • capture
  • f

a free electron and bound electron excitation.

  • radiative stabilization via photon em ission.

Radiative recombination RR

  • non-resonant process
  • capture
  • f

a free electron with photon em ission

Recom bination processes

n=1 n=2 n=∞ Eγ E2 E1 t e beam n=1 n=2 n=∞ Eγ E2 E1 e beam

 

RR q q

A e A    

    1

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SLIDE 3

1s 2s 2p

Ebeam

EB DR RR

 

   

    1 q q

A e A

Binding beam

E E E  

Radiative recombination Radiative recombination Dielectronic recombination Dielectronic recombination

 

 

 

    

      * 1 * * 1 q q q

A A e A

Resonance condition: Eb+E2l=E1s-E2l photon: E~E1s-E2l

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The bare uranium signal U9 2 + at SuperEBI T

10 U92+ ions trapped!

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65 70 75 80 85 90 95 100 105 200 400

69 70 71 72 73 74 75 76 77 78

5 10 15 20

ion abundance (%) Hg ion charge state

Hg K Hg K n=5 n=4 n=3 n=2 j=3/2

Intensity Photon energy (keV)

n=2 j=1/2

Photorecom bination of Hg7 2 + bis Hg7 8 + at 7 2 .5 keV electron beam energy

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4500 4600 4700 4800 4900 5000 5100 5200 5300

10 10

1

10

2

10

3

10

4

10

5

10

6

10

7

4500 4600 4700 4800 4900 5000 5100 5200 5300 1 2 3 4

Electron beam energy (eV) Breeding time (s) Electron beam energy (eV)

X-ray data depending on electron energy

Ions in any desired charge state can be prepared, stored and spectroscopically studied Fe18+...24+ ions are sequentially generated

Fe18+. Fe19+. Fe20+. Fe21+. Fe22+. Fe23+. Fe24+.

interaction time

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DR: as the electron beam energy changes:

 characteristic dielectronic resonances  selectively excited lines

RR: as the electron beam energy changes:

 Photon energy shifts continuosly

Experiment:

  • vary electron beam energy (x-coordinate)
  • measure photon energy (y-coordinate)

Tuning the electron energy

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Electron beam energy ( eV) Photon energy ( eV) 2 2 0 0 3 2 0 0 3 0 0 0 4 0 0 0

He-like Ar 1 6 +

3  1 4  1

DR resonances

n= 2  n= 1 direct excitation

Radiative and dielectronic recom bination

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Measurement technique : DR

51

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Typical DR spectrum

RR n=3 RR n=4 RR n=2

52

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Typical DR spectrum

KLL

n = 2-1 DR

KLM KLN KLO…. DE

n = 3-1 DR n = 4-1 DR

53

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1e QED 4 eV 2e QED 0.2 eV recoil 0.08 eV 0.04 eV uncertainty

  • Fe helium-like and lithium-

like ions studied with electrons

  • X rays detected also with a

high resolution crystal spectrometer

Dielectronic recom bination resonances w ith high resolution

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Hg, Li-like Hg+77 Dielectronic recom bination resonances w ith Hg7 7 +

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Hg, Li-like Hg+77 Zoom into the KLL resonances of different isoelectronic sequences of Hg ions

The element names mean the corresponding isoelectronic sequence, e. g., Be-like: four electrons left, thus Hg76+

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1s 2s1/2 2p1/2 2p3/2

Be-like  B-like

1s 2s1/2 2p1/2 2p3/2

KL1 / 2L1 / 2 KL1 / 2L3 / 2 The KLL resonances and analogously the KL3 / 2L3 / 2

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+ +

DR RR initial state final state

?

Quantum interference betw een DR and RR Fano profile

González et al., Phys. Rev. Lett. 9 4 , 203201 (2005)

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Asym m etry due to quantum interference

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  • nly a few eV accuracy needed

since effects are very large

QED scales w ith Z4

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More complex even: trielectronic and quadruelectronic recombination

  • Resonant many-electron excitations contribute far

more to electronic recombination and Auger decay than expected.

  • This affects radiative energy transfer in stars.
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Dielectronic recombination

Prominent Higher-Order Contributions to Electronic Recombination, C. Beilmann et al., PRL 107, 143201 (2011)

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  • At Z<18, trielectronic processes (TR) dominate the resonant

recombination, even though the number of electrons involved is higher and the process of higher order Trielectronic and quadruelectronic contributions to resonant photorecom bination

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X-ray data depending on electron energy

  • Fe photorecombination studies
  • Slow scans at high electron energy resolution
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  • C. Shah et al., Phys. Rev. E 93

93, 061201(R) (2016)

  • C. Beilmann et al., Phys. Rev. Lett 107

107, 143201 (2011)

  • C. Beilmann et al., Phys. Rev. A 88

88, 062706 (2013)

Unexpected, strong contributions by many-electron resonant excitation at high resolution

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SLIDE 24
  • C. Shah et al., Phys. Rev. E 93

93, 061201(R) (2016)

  • C. Beilmann et al., Phys. Rev. Lett 107

107, 143201 (2011)

  • C. Beilmann et al., Phys. Rev. A 88

88, 062706 (2013)

Unexpected, strong contributions by many-electron resonant excitation at high resolution

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6500 7000 7500 8000 8500 9000 9500 6000 6500 7000 7500 8000 8500 9000 9500 10000 10500 11000 11500 12000 12500 13000

Electron energy (eV) Photon energy (eV)

LMn region of tungsten

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6500 7000 7500 8000 8500 9000 9500

5000 10000 15000 20000

Counts Electron energy (eV)

LMn region of tungsten

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  • Photoionization theory has few

experimental benchmarks for HCI

  • HCI photon opacity data are based largely
  • n untested theory
  • EBIT allows for systematic studies with HCI

along isoelectronic and isonuclear sequences,

Photoionization of HCI

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Photoion extraction and charge analysis

After an interaction time, ions and photoions are extracted, mass selected and detected

electrostatic deflector

gun trap collector

photon beam: 1013 photons/s Wien filter position sensitive detector

Fe14+ Fe15+ B E

monochromator extracted ions X-ray detector

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Photoionizing trapped N3+ at BESSY

EBIT electron beam has to operate below ionization threshold!

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Fe14+ photoionization

  • M. C. Simon et al., Phys. Rev. Lett. 105

105 (2010) 183001

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Current sensitivity for non- resonant photoionization around 20 kbarn

Fe14+ photoionization

Strong resonances allow high resolution nearly reaching natural line width

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Agrees with RMBPT (Gu) at 0.2 eV level

For these ions, HULLAC (A) has errors of few eV, but

  • lder work, e. g., TOPbase typically 10 eV and more!
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SLIDE 33

Doppler shift corrected based on experiment

1 5 . 0 1 5 . 5 1 6 . 0 1 6 . 5 1 7 . 0 1 7 . 5

  • 1

Precise measurements of HCI X-ray absorption line positions and cross sections are possible with EBITs

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Optical spectroscopy with EBITs

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Optical spectroscopy with EBITs

  • No reports about HCI of interest, and no transition data

available for most HCI: Spectral desert

  • HCI production in EBIT easy, identification much harder

50 55 60 65 70 75 80

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80

Atomic number Z

Ionic charge state + 1

1 2 4 8 16 32 64 128 256 512 950

Grey: no lines reported

Color scale: Number

  • f known

transitions Iridium HCI

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Spectroscopy of few-electron ions in the visible range

spectrometer

imaging

  • ptics

electron gun collector SC magnet

trap

CCD Grating spectrometer with cryogenically cooled CCD

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SLIDE 37

Hyperfine structure of the H-like ions

Ground state energy splitting  for an H-like ion scales with Z3

       

rad e p e I

A l j j c m j I m m I n Z                     ) 1 ( 1 1 2 ) 1 (

2 3 3 4

: Breit-Rosenthal effect (8 %)

nuclear charge distribution

: Bohr-Weißkopf effect (2 %)

nuclear magnetization distribution

rad: QED contributions (0.5 %) 

vacuum polarization, self energy Dirac terms

 QED & nuclear structure

Z=1 Z=67 =67 (Ho) (Ho)  6 eV 2 eV Lifetime 11.000.000 years 5 ms

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EBIT EBIT LLNL LLNL ESR ESR GSI GSI

Pb81+

Hyperfine splitting for heavy hydrogen-like ions

GSI storage ring: Klaft et al., PRL 73, 73, 2425 (1994) Seelig et al., PRL 81 4824 (1998)

165Ho66+

HFS= 572.64 nm

JRCLU, P. Beiersdorfer, D. W. Savin, and K. Widmann, PRL 77 77, 826 (1996)

187,185Re74+

HFS= 451.58, 455.92 nm

JRCLU, P. Beiersdorfer, B. B. Birkett, K. Widmann, A.-M. Mårtensson-Pendrill and M. G. H. Gustavsson, PRA 57 57, 879 (1998)

203,205Tl80+

HFS= 385.82, 382.18 nm

  • P. Beiersdorfer, S. B. Utter, K. L.Wong, JRCLU, J. A. Britten, H. Chen, C. L. Harris, R. S. Thoe, D. B. Thorn and
  • E. Träbert, M. G. H. Gustavsson, C. Forssén and A.-M. Mårtensson-Pendrill, PRA 64,

64, 032506 (2001)

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Hydrogenlike Highly Charged Ions for Tests of the Time Independence of Fundamental Constants,

  • S. Schiller, PRL 98,

98, 180801 (2007)

Extremely low systematic frequency shifts

Estimates for systematic frequency shifts in hydrogen-like ions are extremely low: excellent optical clocks possible.

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Our trapped highly charged ions are too hot

Laser spectroscopy with HCI suffers from the deep trapping potential in an EBIT: high ion temperature tunable excitation laser fluorescence imaging Resolution many orders of magnitude worse than in “normal” atomic physics laser spectroscopy

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Laser spectroscopy of forbidden M1 lines

  • V. Mäckel, et al., PRL 107, 143002 (2011), K. Schnorr et al., ApJ 776, 121 (2013)

Evaporative cooling

Ar13+

3 105 K ion temperature

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Fe13+ (Fe XIV): the “green coronal line“

Hendrik Bekker, PRA 2018

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  • Nuclear magnetization distribution in hyperfine

structure of H-like 165Ho66+, 185,187Re74+, 203,205Tl80+.

  • Relativistic nuclear recoil effect in 36,40Ar13+
  • QED and Lamb shift in M1 transitions
  • Astrophysical lines
  • High accuracy M1 lifetime determinations (0.14%)

including EAMM contribution.

EBIT studies with visible lines