Inner Shell Photodetachment of Atomic Negative Ions

1
Inner-Shell Photodetachment of Anions
Nora Berrah, Physics Dept, Western Michigan
University
Funded by NSF DoE, BES
2
Adventures! Dardjeeling, India
3
Inner-Shell Photodetachment of Anions

• Outline
• ?? Doubly and Triply Excited States
• ?? Significant PCI Effects
• ?? Shape and Feshbach Resonances
• ?? Threshold Phenomena
• ?? Production of Highly Charged Ions

4
Why are Negative Ions Fundamental Exotic
Systems?

• Negative Ions are Test systems for
• Short range potentials
• Electron-electron correlation models(e.g.
  accounts for gt half the EA of F)

h? X- ? X e-
h? X ? X e-
Status ? Least studied of atomic or molecular
systems ? Theoretical work available ?
Inner-shell processes largely unexplored (new
field 2001) ? Exp. Facilities ALS, ASTRID,
Spring-8, SOLEIL
5
Photodetachment of Negative Ions

• Valence-Shell Photodetachment
• h? A- ? A e-
• Inner-Shell Photodetachment
• h? A- ? A e-ph
• ? A e-ph
• ?
• A e-A e-ph

6
Photodetachment of He_ Part1 Probing Doubly and
Triply Excited Resonances
7
K-Shell Photodetachment of He- 1s2s2p 4P
Single photon
Probing Doubly and Triply Excited States!!
Hollow Ion/Atom
8
K-Shell Photodetachment of He- Comparison
Between Two Calculations in Dispute
Berrah, Bozek, Turri, Ackerman, Rude, Zhou,
Manson, PRL 88, 093001 (2002).
9
Comparison with an Additional Calculation
10
Photodetachment of He- near the 1s threshold
Absolute cross-section measurements and
postcollision interactions
Sanz-Vicario et al. PCI S-V (PCI) scaled by 1.13
No PCI No PCI Shifted
Bilodeau, Bozek, Agular, Ackerman, Berrah, PRA
73, 034701 (2006).
11
Triply Excited States??? Need Higher
Resolution data..
12
Photodetachment of He- Part 2 Simultaneous
Double Auger Decay
13
He- 2s2p2 4P Simultaneous Double Auger Decay
He
Total cross section (theory) ? 600 Mb DA cross
section ? 60 Mb (Other small (3 or 4 e-) systems
ltlt 1Mb) ERes D Experiment 37.668(7) Sanz-V
icario (2002) 37.669 0.001 (CSCI) Zatsarinny
(2002) 37.685 0.017 (R-M) Zhou (2001) 37.703 0.035
(R-M)
Bilodeau , Bozek, Ackerman, Berrah, PRL 93,
193001 (2004).
14
Feshbach Resonance/Double Auger Decay
He- 1s Excitation
hn
Double Auger Decay (3-electrons interaction)
Bilodeau , Bozek, Ackerman, Berrah, PRL 93,
193001 (2004).
15
Photodetachment of He_ Part3 Near-Threshold
Photodetachment
16
Threshold Law The Wigner Law?

• ?0?e l 1/2
• ?0 amplitude
• ?e h?- ?t photoelectron energy
• ?t threshold energy
• l l0 ? 1 l0 angular Momentum of the detached
  electron
• s-detachment, l0 0, l 1? p outgoing wave (He-)
• p-detachment, l01, l 1?1, s , d outgoing wave
  (S-)

17
He- 2s2p Threshold Region Validity of the Wigner
Law??
Bilodeau et al., PRL 95, 083001, 05
18
Wigner Law is Valid Near Threshold in He-!
-.-.Vicario,no PCI Vicario, PCI p-Wave
Wigner Law Fit
2s2p 3P0
PC Shift ? 15 meV
? Shape not Altered by PCI
Predicted Threshold Energy
Bilodeau, Bozek,Gibson,Walter, Ackerman,
Dumitriu, Berrah, Phys. Rev. Lett. 95, 083001
(2005).
19

• How about Heavier Targets???
• What Type of Phenomena or Processes Occur
  subsequent to Inner-Shell Photodetachment??

20
2p Photodetachment of S-
High Charge State Formation!
S2/S? 60
Li3/Li2lt1
Th Sim-Auger
Int K-Out
H S-Off or S-UpSeq-Aug
21
2p Photodetachment Threshold for S, S2 and S3
s-Wave Wigner Law Valid for All Channels !!!
22
2p Threshold Photodetachment in S-.
Threshold investigation in S and S 3 Charge
States
s-wave Wigner law fit
Bilodeau, Bozek, Gibson, Walter, Ackermann and
Berrah, PRL Phys. Rev. Lett. 95, 083001 (2005).
23
2p Threshold Photodetachment in S- (3s2 3p5 2P)
Threshold Investigation in S 2 Charge State
sd-wave Wigner law fit s-wave
Wigner law fit
3 eV range validity!! Compared to 0.01-0.1 eV for
valence e-
24
2s Photodetachment Threshold for S, S2 and S3
2s ?3p Feshbach resonance, below 2s threshold in
all three Channels!?
S- state 2s-13s23p6 2S1/2
Fano profile p-wave Wigner law
2sThreshold
Bilodeau et al. PRA 72, 050701(R), (2005).
25
Transition Metals Negative Ions d-Orbital
Excitations in (Ni-, Pd-, Pt-)
Ni- 3d94s2 ? 3p ? d excitation
Pd- 5d105s1 ? p ? s excitation (no shape
resonance)
Pt- 4f145d96s2 ? p,f ? d excitation
26
Excitation Detachment in Pt- 5p and 4f
27
Summary

• Sequential Auger decay in He- hollow-ion
  states - Significant progress in agreement with
  theory for cross sections, nature and
  positions of structures
• Simultaneous double-Auger decay in 1s detachment
  of He- - First measurement of the 2s2p2 4P
  state - First observation of a DA decay in a
  negative ion
• p excitation in S- (and Si-) with multiple charge
  production - Multi-Auger decay and/or other
  multi-electron processes
• p- and f-electron to d-orbital excitation in Pt-
  - Large shape and Feshbach resonances in
  transition metal negative ions

28
The Team
29
Chairs J. Tanis N. Berrah