Stimulated X-ray Emission Spectroscopy with hard X-rays · 2019-07-30 · 2 KMn(VII)O 4 KMnO 4 norm...
Transcript of Stimulated X-ray Emission Spectroscopy with hard X-rays · 2019-07-30 · 2 KMn(VII)O 4 KMnO 4 norm...
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Stimulated X-ray Emission Spectroscopy with hard X-rays
Thomas Kroll
SLAC National Accelerator Laboratory
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Acknowledgement
Lawrence Berkeley National LabVittal Yachandra Junko YanoJan KernFranklin Fuller
SLACUwe BergmannClemens WeningerY. ZhangRoberto Alonso-MoriAgostino MarinelliAlberto LutmanMarc W. Guetg
CXI Instrument at LCLSSebastien BoutetAndy AquilaJake KoralekDan DePonte
Funding: DOE and NIH
Max Planck, Hamburg, Germany Nina RohringerLaurent MercadierVinay P. Majety
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Mn(II)OMn(IV)O2
KMn(VII)O4
KMnO
4 nor
m
Relative Energy [eV] 350
Inte
nsit
y [a
.u.]
Ka1
Kb''
Kb'
Kb2,5
Kb1,3
Ka2
Valencelevels
3p
2p
1s
Kα1,2
Kβ1,3, Kβ’
Kβ2,5, Kβ’’
Level Diagram
X-Ray Emission Spectroscopy
Spin/oxidation state of transition metals
Valence orbitals: ligand type, structure, covalency, ligand protonation, etc
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Bergmann et al, J Synchr Rad. 8, 199 (2001)
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Stimulated X-ray Emission Spectroscopy
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Ø Low photon flux density (only a few photons at a time in the sample)
Ø Only spontaneous emission in 4p direction
Stimulated (non-linear) emission:Spontaneous (conventional) emission
Incoming photons:(> abs. energy)
KaKb
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Stimulated X-ray Emission Spectroscopy
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Ø Very high flux density (~1011 ph / 10 fs / 100x150 nm2)
Ø Creation of population inversion
Ø Non-linear effects become dominant
Ø Cascade like decay
Stimulated (non-linear) emission:Amplified spontaneous emission (ASE)
Pump:(> abs. energy)
KaKb
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Experimental Setup
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- Highly focused 10 fs beam (100 x 150 nm2)
- Flat crystal analyzer in forward direction
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Objectives
• Can stimulated XES be applied to transition metal solutions?
• What is fundamentally new information provided by stimulated XES techniques that is not achievable with other techniques?
• Can stimulated XES be used for chemically sensitive X-ray emission lines? Is the chemical information preserved?
• Can we stimulate the weaker Kb emission?
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Single shot spectra (Ka-ASE)
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Single shots:
o Clean curve in single shot
o Only the Ka1 visible
o FWHM < normal Ka width
MnCl2 solution
5890 5895 5900 5905
5900 59105890
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Lasing in MnCl2 solution
5904590058965892Emission energy (eV)
Proof of Lasing:
- Exponential increase
- Linear gain regime below ~2 mJ
- Saturation reached > 2 mJ
T. Kroll et al. Phys. Rev. Letter 120, 133203 (2018)
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Peak Position and Width
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o Low to mid high photon numbers:
o Constant broadening and position
o High photon numbers:
o Spectral broadening
o Shift to lower energies
o Variations through beam position,
temporal shape, lasing condition
5904590058965892Emission energy (eV)
T. Kroll et al. Phys. Rev. Letter 120, 133203 (2018)
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Peak Position and Width
11T. Kroll et al. Phys. Rev. Letter 120, 133203 (2018)
o Line broadening due to saturation effects
o Additional final states become visible
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Peak Position and Width
12T. Kroll et al. Phys. Rev. Letter 120, 133203 (2018)
1.0
0.8
0.6
0.4
0.2
0.0-4 -2 0 2 4
Relative photon energy (eV)
1.1 eV
o Mn Ka1 life-time broadening: 1.48 eV (Krause and Oliver, 1979)
o Lowest observed S-XES peak width: < 1.0 eV
o Darwin width of Si (111): 0.77 eV
o Lowest S-XES lifetime broadening: < 0.5 eV
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Stimulated X-ray Emission Spectroscopy
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Ø Kb Seed pulse outruns Ka emission → seeded stimulated Kb emission
Ø Requirement: Overlap in time, space and energy
Stimulated (non-linear) emission:Amplified spontaneous emission (ASE) + seeded stimulated emission
Pump:> abs. energy
Seed:Kb energy Ka
Kb
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Experimental Setup
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- Highly focused 10 fs beam (100 x 150 nm2)
- Use part of the undulators for seed pulse
- Two flat crystals in series in forward direction for simultaneous detection of Ka and Kb
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Seeded Stimulated Kb emission
Biggest issue:
- Seed pulse and stimulated emission are at the same energy
- How to separate the stimulated signal from the SASE seed pulse?
Pump:> abs. energy
Seed:Kb energy
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Conclusions
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• Strongly stimulated XES in Mn solutions has been observed • Gain curves for X-ray lasing have been measured• Gain narrowing to less than the natural line width• Chemical information appears to be preserved!• Seeded stimulated Kb emission observed
Future• Improved diagnostics:
• especially in time domain
• Seeded beam diagnostic
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Stimulated X-ray Emission has been observed
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Past achievements:
Soft X-rays
- Stimulated soft X-ray Ne laser
(Rohringer et al, Nature 481, 488 (2012), LCLS)
- Ne gas
- Stimulated X-ray Emission in Silicon L Lines (70-100 eV)
(Beye et al, Nature 501, 191 (2013), LCLS)
- Si
Hard X-rays
- Stimulated hard X-ray Fe laser
(Yoneda et al., Nature 524, 446 (2015), SACLA)
- Fe foil
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High number of photons:
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Varying pulse energy:
o Increase of Ka2 for high fluences
o Can be explained by final state effects
0.001
0.01
0.1
1
-10 -5 0 5relative photon energy (eV)
MnCl2 FWHM: 2.2 eV 3.3 eV 4.6 eV
Cu foil(Yoneda et al.,Nature 524, 446 (2015))
T. Kroll et al. Phys. Rev. Letter 120, 133203 (2018)
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Chemical Sensitivity
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Compare solution spectra:
o Stimulated data retain the
expected chemical shift
o Need to address stimulated
photon / matter interaction in
more detail
T. Kroll et al. Phys. Rev. Letter 120, 133203 (2018)
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Experimental Setup
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LCLS @ SLAC Linear Accelerator Laboratory
- > 3 km long building
- Electrons are accelerated
- Undulators create photons
- Pulsed and highly focused beam
- Large number of photons per pulse:
- 1011 per pulse of 10 fs
X-ray Free Electron Laser: LCLS