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Atomic Physics with VUV-FEL Radiation

I. SASE FEL Radiation (Self Amplification of Spontaneous Emission Free Electron Laser) Unique Light Sources VUV-FEL User Facilities. II. Multi-Photon Processes in Atoms & Molecules Interactions with Molecular Ions Spectroscopy & Ionisation of Ions.

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Atomic Physics with VUV-FEL Radiation

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  1. I. • SASE FEL Radiation (Self Amplification of Spontaneous Emission Free Electron Laser) • Unique Light Sources • VUV-FEL User Facilities II. • Multi-Photon Processes in Atoms & Molecules • Interactions with Molecular Ions • Spectroscopy & Ionisation of Ions Atomic Physics with VUV-FEL Radiation R. Moshammer MPIK-Heidelberg

  2. From Synchrotron Radiation to FEL-Light bunch of Ne electrons Undulator Synchrotron-Radiation Power  Ne

  3. From Synchrotron Radiation to FEL-Light bunch of Ne electrons Undulator Synchrotron-Radiation Power  Ne

  4. FEL-Radiation From Synchrotron Radiation to FEL-Light bunch of Ne electrons Undulator Power  Ne2 Self Amplified Spontaneous Emission (SASE)

  5. measured Sept. 2001 From Synchrotron Radiation to FEL-Light Gain in Quality & Power: 5-8 Orders of Magnitudes

  6. proposed FEL’s High-Power Laser versus FEL

  7. Non-Linear Processes in Atoms (Molecules) • Atomic Reactions with Small Cross-Sections Unique Light Sources Full coherence: ....... Dl/l 10-4 ... 10-8 Photon energies: ..... 10 eV to 10 keV Pulse width : ......... DT < 100 fs Rep. Rate : ............. up to 70 kHz Photons / Pulse : ..... 1012 Peak-Power : .......... MW to GW Intensities: .............. I > 1016 W/cm2

  8. VUV-FEL User Facilities Proposed Facilities BESSY: Eg < 1 keV SLAC : Eg < 8 keV TESLA : Eg < 14 keV Daresbury, Spring8, ........... Under construction TESLA Test Facility (TTF at DESY Hamburg) Start of user experiments in 2004 Eg < 200 eV

  9. Hamburg: TESLA Test Facility (TTF)

  10. Atomic Physics(Approved TTF - Experiments) • Multi-Photon Processes in Atoms & Molecules • Interactions with Molecular Ions • Spectroscopy & Ionisation of Ions Universität Frankfurt: R. Dörner, L. Schmidt, Th. Weber Fritz-Haber Institut Berlin: U.Becker Universität Hamburg: B. Sonntag Max-Planck-Institut Heidelberg: R. Moshammer, A. Dorn, D. Fischer, C.D. Schröter, J. Ullrich Max-Planck-Institut Heidelberg: H.B. Pederson, A. Wolf, D. Schwalm, J. Ullrich Weizmann Institute Rehovot: D. Zajfmann Max-Planck-Institut Heidelberg: J.R. Crespo,J. Braun,J. Bruhns, A. Dorn, R. Moshammer, C.D. Schröter, J. Ullrich Fudan University Shanghai Y. Zou LLNL Livermore P. Beiersdorfer

  11. Atomic Physics • Multi-Photon Processes in Atoms & Molecules • Interactions with Molecular Ions • Spectroscopy & Ionisation of Ions

  12. Atomic Physics • Multi-Photon Processes in Atoms & Molecules • Interactions with Molecular Ions • Spectroscopy & Ionisation of Ions

  13. Reaction-Microscope Drift Detector position-sensitive, multi-hit Helmholtz coils Spectrometer: Ion-electron coincidence meV ion energy resolution meV electron resolution El. field Supersonic gas jet Atoms, Molecules FEL Experimental Approach

  14. Experimental Approach Ion-detector Laser beam Gas-jet Electron-detector • Ultra high vacuum : p < 10-11 mbar • Ultra cold gas-jet : T < 1 Kelvin • Multi-hit detectors :  = 12 cm, Dt ~ 10 ns

  15. Single Photon Many Photons Few Photons hn << Ip FEL hn > Ip High Intensity Lasers I = 1015 W/cm2 Synchrotron-Radiation Ionisation of Atoms From Single Photons to Many Photons

  16. From Single Photons to Many Photons Few Photons ? e e Electron-Energy Ee Electron-Energy Ee Single Photon Many Photons Dörner (1997) Tunneling 1015 W/cm2

  17. From Single to Double Ionization e e -10 -5 5 10 0 P|| /a.u. Single Photon Many Photons Dörner et al. (2001)

  18. From Single to Double Ionization e e e1 e1 e2 e2 Single Photon Many Photons ! many open questions ! ! well understood !

  19. Experiment Theory (Goreslavski et al.) P|| (e2) [a.u.] e- momentum P|| (e1) [a.u.] Exp.: MBI-Berlin, MPI-Heidelberg, Frankfurt, Marburg...... Theory: Becker, Faisal, Taylor, Goreslavski..... Problems: • too many photons • classical field  ponderomotive motion

  20. possible Mechanisms: Dt + + 1 3 2 “Few” Photons: FEL - Radiation Helium ponderomotive potential Up I/w2 0 e.g. Eg= 50 eV

  21. + + energy [eV] -24 Dt -54 Helium -79 1 3 3 3 3 2 2 2 1 1 electron energy

  22. 1 hn Multi-Photon Double Ionization 2 hn momentum electron 1 [a.u.] 3 hn momentum electron 2 [a.u.] Perturbation theory Colgan & Pindzola PRL 88 (2002) Two-Photon Absorption at hn = 45 eV Numerical Solution of the Schrödinger-Equation Parker & Taylor J. Phys. B34 (2001) Absorption above threshold hn = 87 eV I = 2.1016 W/cm2

  23. More Processes • Multi-photon • single ionisation • Two-photon • innershell ionisation R. Hasbani, E. Cormier and H. Bachau J. Phys. B 33 (2000) 2101 S.A. Novikov and A.N. Hopersky J. Phys. B 33 (2000) 2287

  24. Atomic Physics • Multi-Photon Processes inAtoms & Molecules • Interactions with Molecular Ions • Spectroscopy & Ionisation of Ions

  25. Molecules: Fixed-in-Space Auger e e 10 eV O Shigemasa et al. PRL 74 (1995) Heiser & Becker et al. PRL 79 (1997) C Landers & Dörner PRL 87 (2001) “Molecules illuminated from within”

  26. hn2 probe hn2 hn1 pump Fixed-in-Space & Pump-Probe U. Becker, R. Dörner photo-electron angular distribution • “Snapshots” of the time-evolution • of intra-molecular potentials • “Movie” of the dissociation reaction fs time-scale for dissociation

  27. Atomic Physics • Multi-Photon Processes inAtoms & Molecules • Interactions with Molecular Ions • Spectroscopy & Ionisation of Ions

  28. VUV Photodissociation of Molecular Ions R A. Wolf, D. Zajfman, D. Schwalm Direct Predissociation Spontaneous radiative diss. Energy

  29. Experimental Approach A. Wolf, D. Zajfman, D. Schwalm Photon induced Dissociation Photodissociation Imaging electrostatic ion beam trap Hollow cathode ion source 5 kV Einzel lens VUV FEL Molecular ions e.g. CH+ Cold molecular ions Relaxation time (CH+) ~ 0.4 sec • Extracted ion bunch • extraction time ~ 50 ns • ~ 10 pulses per fill of trap • Kinetic energy release • Angular distributions • Cross sections

  30. CO CH+ HCO+ H2 H2+ H3+ Interstellar cloud chemistry Example: CH+ (production of oxygen-bearing molecules) e- C CO hn H2 e- from Hartquist, Williams Cambridge Univ. Pr. 1995

  31. CO HCO+ H2 H2+ H3+ Interstellar cloud chemistry Example: CH+ (production of oxygen-bearing molecules) loss mechanism photodissociation e- CH+ C CO hn Ex: Diffuse Cloud (ξ Ophiuchi): NObser(CH+) = 2.9·1013 cm-2 NModel(CH+) = 2.8·1010 cm-2 H2 e- from Hartquist, Williams Cambridge Univ. Pr. 1995

  32. H2O+ • Relevant Photon Energies: • Interstellar clouds: < 13.6 eV • Close to stars: < 50 eV H3O+ CHn+ estimated NHn+

  33. FEL -Radiation !! H2O+ • Relevant Photon Energies: • Interstellar clouds: < 13.6 eV • Close to stars: < 50 eV H3O+ CHn+ estimated NHn+

  34. Atomic Physics (Approved TTF - Experiments) • Multi-Photon Processes in Atoms & Molecules • Interactions with Molecular Ions • Spectroscopy & Ionisation of Ions

  35. 1 m Experimental Approach J. Crespo, P. Baiersdorfer, J. Ullrich FEL-apparatus: (under construction) FEL beam   

  36. Precision Spectroscopy on Ions I. Test of 1e - QED at Z ~ 1II. Few-Electron QEDIII. Determination of Nuclear Properties Magnetisation Distribution Magnetic Moment distribution Charge Radius Neutron DistributionIV. Electroweak Radiative Corrections V. Life Time Measurements FEL-Light: Dl/l < 10-4

  37. no data typical exp. accuracy: EE = 10-3-10-5 Lamb-shift in Li-like Ions BEVALAC (U89+) 280.59  0.10 eV FEL bandwidth: l/l 10-4 Expected accuracy: ll 10-6 QED contribution

  38. Photoionization of Ions • very few data (luminosity) • urgently needed (opacity project) • Multi-Photon Ionization! • Above Threshold Ionization! • Few photon – Few electrons! • High Harmonic Generation • Differential Data • differential data (merged beams) Photo ionization near threshold: Fe XV [2p63s2(1S)] R-matrix OP cross sections M. A. Bautista J. Phys. B 33 (2000) L419

  39. Extracted Beams from the EBIT combine FEL-radiation Future: Exciting LEIF with FEL‘s

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