Atomic Physics with VUV-FEL RadiationR. Moshammer MPIK-Heidelberg

• SASE FEL Radiation (Self Amplification of Spontaneous Emission Free Electron Laser) • Unique Light Sources• VUV-FEL User Facilities

I.

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

II.

bunch of Ne electrons Undulator

Synchrotron-Radiation

From Synchrotron Radiation to FEL-Light

Power Ne

bunch of Ne electrons Undulator

Synchrotron-Radiation

From Synchrotron Radiation to FEL-Light

Power Ne

From Synchrotron Radiation to FEL-Light

Undulator

Self Amplified Spontaneous Emission (SASE)

bunch of Ne electrons

Power Ne2

FEL-Radiation

measuredSept. 2001

From Synchrotron Radiation to FEL-Light

Gain in Quality & Power:5-8 Orders5-8 Orders of Magnitudes

High-Power Laser versus FEL

proposedFEL’s

Full coherence: ....... / 10-4 ... 10-8

Photon energies: ..... 10 eV to 10 keVPulse width : ......... T < 100 fsRep. Rate : ............. up to 70 kHzPhotons / Pulse : ..... 1012

Peak-Power : .......... MW to GWIntensities: .............. I > 1016 W/cm2

• Non-Linear Processes in Atoms (Molecules)• Atomic Reactions with Small Cross-Sections

Unique Light Sources

Proposed FacilitiesBESSY: E < 1 keV SLAC : E < 8 keVTESLA : E < 14 keV

Daresbury, Spring8, ...........

Under constructionTESLA Test Facility (TTF at DESY Hamburg)

Start of user experiments in 2004 E < 200 eV

VUV-FEL User Facilities

Hamburg: TESLA Test Facility (TTF)

• Multi-Photon Processes in Atoms & Molecules

• Interactions with Molecular Ions

• Spectroscopy & Ionisation of Ions

Atomic Physics (Approved TTF - Experiments)

Universität Frankfurt: R. Dörner, L. Schmidt, Th. WeberFritz-Haber Institut Berlin: U. BeckerUniversität Hamburg: B. SonntagMax-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. ZouLLNL Livermore P. Beiersdorfer

• Multi-Photon Processes in Atoms & Molecules

• Interactions with Molecular Ions

• Spectroscopy & Ionisation of Ions

Atomic Physics

Atomic Physics

• Multi-Photon Processes in AtomsMulti-Photon Processes in Atoms & Molecules

• Interactions with Molecular Ions

• Spectroscopy & Ionisation of Ions

Experimental Approach

Supersonic gas jetAtoms, MoleculesFELFEL

Spectrometer: Ion-electron coincidenceeV ion energy resolutionmeV electron resolution

Drift

Detectorposition-sensitive, multi-hit

Helmholtz coils

Reaction-Microscope

El. field

• Ultra high vacuum : p < 10-11 mbar• Ultra cold gas-jet : T < 1 Kelvin• Multi-hit detectors : = 12 cm, t ~ 10 ns

Laser beam

Ion-detector

Gas-jet

Electron-detector

Experimental Approach

From Single Photons to Many Photons

Ionisation of Atoms

High Intensity Lasers I = 1015 W/cm2

h << Ip

Many PhotonsSingle Photon

h > Ip

Synchrotron-Radiation

Few Photons

FELFEL

Single Photon

From Single Photons to Many Photons

Tunneling1015 W/cm2

Electron-Energy EeElectron-Energy Ee

Many PhotonsFew Photons

?Dörner (1997)

Dörner et al. (2001)

From Single to Double Ionization

Single Photon

P|| /a.u.

-10 -5 100 5

Many Photons

Single Photon Many Photons

e2

e1 e2e1

! well u

nderstood !

! man

y open

questio

ns !

From Single to Double Ionization

e- momentum P|| (e1) [a.u.]

P|| (

e 2)

[a.u

.]

Experiment

• too many photons• classical field ponderomotive motion

Theory (Goreslavski et al.)

Exp.: MBI-Berlin, MPI-Heidelberg, Frankfurt, Marburg......Theory: Becker, Faisal, Taylor, Goreslavski.....

Problems:

“Few” Photons: FEL - Radiation

Helium

ponderomotive potentialUp I/2 0

t

1 32

+ +

possible Mechanisms:

e.g. E= 50 eV

ene

rgy

[eV

]

-24

-54

-79Helium

1 32

electron energy

2 1

3 3

t

31

+

2

+

Multi-Photon Double Ionization

Numerical Solution of theSchrödinger-EquationParker & Taylor J. Phys. B34 (2001)

h = 87 eVI = 2.1016 W/cm2

momentum electron 1 [a.u.]

mom

entu

m e

lect

ron

2 [a

.u.]

Perturbation theoryColgan & Pindzola PRL 88 (2002)

Two-Photon Absorption at h = 45 eV

1 h 2 h

3 h

Absorption above threshold

• Multi-photon single ionisation

• Two-photon innershell ionisation

More Processes

R. Hasbani, E. Cormier and H. Bachau J. Phys. B 33 (2000) 2101

S.A. Novikov and A.N. HoperskyJ. Phys. B 33 (2000) 2287

• Multi-Photon Processes in Atoms & MoleculesMolecules

• Interactions with Molecular Ions

• Spectroscopy & Ionisation of Ions

Atomic Physics

Molecules: Fixed-in-Space Shigemasa et al. PRL 74 (1995)Heiser & Becker et al. PRL 79 (1997)

Landers & Dörner PRL 87 (2001)

“Molecules illuminated from within”

C

O

10 eV

Auger

pump

h1

h2

h2

probe

Fixed-in-Space & Pump-Probe

photo-electron angular distribution

fs time-scale for dissociation

• “Snapshots” o

f the tim

e-evolution

of in

tra-m

olecular potentials

• “Movie” o

f the dissociation re

action

U. Becker, R. Dörner

Atomic Physics

• Multi-Photon Processes in Atoms & Molecules

• Interactions with Molecular IonsInteractions with Molecular Ions

• Spectroscopy & Ionisation of Ions

VUV Photodissociation of Molecular IonsA. Wolf, D. Zajfman, D. Schwalm

Ene

rgy

R

Direct Predissociation

Spontaneousradiative diss.

Hollow cathode ion source 5 kV

electrostatic ion beam trap

Einzel lens

• Kinetic energy release• Angular distributions• Cross sections

Cold molecular ionsRelaxation time (CH+) ~ 0.4 sec

VUV FEL

Extracted ion bunch• extraction time ~ 50 ns• ~ 10 pulses per fill of trap

Experimental Approach

PhotodissociationImaging

A. Wolf, D. Zajfman, D. Schwalm

Molecular ionse.g. CH+

Photon induced Dissociation

from Hartquist, Williams Cambridge Univ. Pr. 1995

H2 H2+

CH+

H3+

CO

HCO+

e-

C

h

e-

H2

Interstellar cloud chemistryExample: CH+ (production of oxygen-bearing molecules)

CO

from Hartquist, Williams Cambridge Univ. Pr. 1995

H2 H2+

CH+

H3+

CO

HCO+

e-

C

h

e-

H2

Interstellar cloud chemistryExample: CH+ (production of oxygen-bearing molecules)

loss mechanism

photodissociation

COEx: Diffuse Cloud (ξ Ophiuchi): NObser(CH+) = 2.9·1013 cm-2 NModel(CH+) = 2.8·1010 cm-2

estim

ated

CHn+

H2O+

H3O+

NHn+

Relevant Photon Energies:

• Interstellar clouds: < 13.6 eV• Close to stars: < 50 eV

estim

ated

CHn+

H2O+

H3O+

NHn+

Relevant Photon Energies:

• Interstellar clouds: < 13.6 eV• Close to stars: < 50 eV

FEL -Radiation !!

• Multi-Photon Processes in Atoms & Molecules

• Interactions with Molecular Ions

• Spectroscopy & Ionisation of IonsSpectroscopy & Ionisation of Ions

Atomic Physics (Approved TTF - Experiments)

1 m

FEL-apparatus:(under construction)

FEL beam

Experimental Approach J. Crespo, P. Baiersdorfer, J. Ullrich

Precision Spectroscopy on Ions

I. Test of 1e - QED at Z ~ 1

II. Few-Electron QED

III. Determination of Nuclear Properties

Magnetisation Distribution

Magnetic Moment distribution

Charge Radius

Neutron Distribution

IV. Electroweak Radiative Corrections

V. Life Time Measurements

FEL-Light:

/

Lamb-shift in Li-like Ions

QED contributionFEL bandwidth: / 10-4

Expected accuracy: 10-6

BEVALAC (U89+) 280.59 0.10 eV

no datatypical exp.accuracy:

EE = 10-3-10-5

• urgently needed (opacity project)

Photoionization of Ions• very few data (luminosity)

• differential data (merged beams)

M. A. BautistaJ. Phys. B 33 (2000) L419

Photo ionization near threshold:

Fe XV [2p63s2(1S)]

R-matrix

OP cross sections

• Multi-Photon Ionization!

• Above Threshold Ionization!

• Few photon – Few electrons!

• High Harmonic Generation

• Differential Data

Extracted Beams from the EBIT

combine

FEL-radiation

Future: Exciting LEIF with FEL‘s