John T. CostelloNational Centre for Plasma Science & Technology (NCPST) and School of Physical Sciences, Dublin City Universitywww.physics.dcu.ie/~jtc & john.costello@dcu.ie

Photoabsorption Spectroscopy & Imaging with Laser-Plasma X-VUV Continua

(Atomic Photoionization with LPP)

Interchannel interaction in photoionization of atoms and photodissociation of molecules, Riezlern, Austria July 12, 2005

Outline of Talk

Part I - Laser Plasma 'Line-Free' Continuum Sources Origin, Brief History & Update

Part II - Dual Laser Plasma Experiments - Some Case Studies X-VUV Photoabsorption Spectroscopy VUV (Monochromatic) Photoabsorption Imaging

Part III - Next Steps Atomic Photoionization Photoionization of Atoms in Intense Laser Fields - ‘Pump

Probe’ Experiments with X-VUV FELs

Collaborators and ContributorsPicosecond X-VUV Continuum SourcesRAL - E Turcu & W ShaikhQUB - C Lewis, R O'Rourke and A MacPheeDCU - O Meighan and C McGuinness

EUV Absorption SpectroscopyRostov - P Demekhin, B Lagutin and V SukhorukovDCU - P Yeates, A Neogi, C Banahan, D Kilbane, P van Kampen and

E Kennedy

VUV Photoabsorption Imaging Facility - VPIFPadua -P Nicolosi and L Poletto DCU - J Hirsch, K Kavanagh, E Kennedy & H de Luna

DESY ‘Pump Probe’ Project Hasylab- J Feldhaus, E Ploenjes, K Tiedke, S Dusterer & R TreuschOrsay- Michael Meyer, Denis Cubyannes & Patrick O'Keefe, DCU- E Kennedy, P Yeates, J Dardis and P Orr (QUB)

'Colliding Plasmas'DCU - K Kavanagh, H de Luna, J Dardis and M Stapleton

Academic Staff (4): John T. Costello, Eugene T. Kennedy (now VPR), Jean-Paul Mosnier and Paul van Kampen (on sabbatical)

Post Doctoral Fesearchers (5): Dr. Deirdre Kilbane (PVK/JC) Dr. Hugo de Luna (JC)Dr. Mark Stapleton (JC)Dr. Jean-Rene Duclere (JPM) Dr. Pat Yeates (ETK)

Current PhD students (6): Caroline Banahan (PVK/JC)Kevin Kavanangh (JC) Adrian Murphy (JC)John Dardis (JC) Rick O'Hare (JPM), Eoin O’Leary (ETK)

Visiting PhD students: Domenico Doria (Lecce) and Philip Orr (QUB)

The LPP node comprises 6 laboratory areas focussed on pulsed laser matter interactions (spectroscopy/ imaging)

Laser-Plasma/Atomic Phys-NCPST

Funded by:SFI - Frontiers and InvestigatorHEA - PRTLI and North-SouthIRCSET - Embark & BRGSEnterprise Ireland - BRGSEU - Marie Curie and RTD

Part I - Laser Plasma Continua

Laser Plasma Source Parameter Range

Target

Lens

Laser Pulse 1064 nm/0.01 - 1 J/ 5ps - 10 ns

Spot Size = 50 m (typ.)

: 1011 - 1014 W.cm-2

Te : 10 - 1000 eV

Ne: 1021 cm-3

Vexpansion 106 cm.s-1

Emitted -Atoms,Ions,

Electrons,Clusters,

IR - X-ray Radiation

PlasmaAssisted

Chemistry

Vacuum orBackground Gas

What does a laser plasma look like ?

PLASMAGENERATION

PLASMAEXPANSION

FILMGROWTH

Target

IncidentLaserbeam

Expanding PlasmaPlume

Substrate

Intense Laser Plasma Interaction

S Elizer, “The Interaction of High Power Lasers with Plasmas”, IOP Series in Plasma Physics (2002)

Laser Produced ‘Rare Earth’ Continua -Physical Origin, History & Update

Laser Plasma Rare Earth Continua

P K Carroll et al., Opt.Lett 2, 72 (1978)

What is the Origin of the Continuum ?

Continua emitted from laser produced

rare-earth (and neighbouring elements)

plasmas are predominantly free-bound in

origin and overlaid by Unresolved Trans-

ition Arrays (UTA*) containing many

millions of lines which share the available

oscillator strength.

* J. Bauche, C. Bauche-Arnoult & M. Kalpisch, Phys. Scr 37, 659 (1988)

But why is no line emission observed ?Line emission is due to complex 4d-4f arrays in (typically) 7 - 20 times ionized atoms

4dn5sq5ps4fm 4dn-15sr5pt 4fm+1, q+s = r+t

Furthermore 4f/5p and 4f/5s level crossing gives rise to overlapping bands of low lying configurations, most of which are populated in the ~100 eV plasma

Result - the summed oscillator strength for each 4d - 4f (XUV) and 5p - 5d (VUV) array is spread out over a supercomplex of transitions producing bands of unresolved pseudo continua (so called ‘UTA’) superimposed on the background continuum

Even expectedly strong lines from simple 4f - 4f arrays are washed out by plasma opacity

There are up to 0.5 million allowed transitions in LS couplingover the ~10 eV bandwidth of a UTA

In fact this is a lower bound since many additional LS forbidden transitions are ‘switched on’ by the breakdown in LS coupling here - G O’Sullivan et al., J.Phys.B 32, 1893 (1999)

Brief History/ Highlights of Laser Plasma Rare-Earth’ Continua -1990

1. First report of line free continua - P K Carroll et al., Opt.Lett 2, 72 (1978)

2. First full study/ applications - P K Carroll et al., Appl.Opt. 19, 1454 (1980)

3. VUV Radiometric Transfer Standard - G O’Sullivan et al., Opt.Lett 7, 31 (1982)

4. Absolute Calibration with Synchrotron - J Fischer et al, Appl.Opt. 23, 4252 (1984)

5. Photoelectron Spectroscopy - Ch. Heckenkamp et al., J.Phys.D 14, L203 (1981)

6. First Study for XUV lithography - D J Nagel et al., Appl.Opt. 19, 1454 (1980)

7. XUV Reflectometer - S Nakayama et al., Physica Scripta 41, 754 (1990)

8. First Industrial Application - DuPont - Insulator Band Structure

VUV Reflectance Spectroscopy - R H French, Physica.Scripta 41, 404 (1990) -

System subsequently made available commercially from ARC

For a review of the early years (1,2) and more recent work (3)including applications in photoabsorption spectroscopy see :1. J T Costello et al., Physica Scripta T34, 77 (1991)2. P Nicolosi et al., J.Phys.IV 1, 89 (1991)3. E Kennedy et al., Radiat. Phys. Chem 70, 291 (2004)

Recent Developments in LP Continua Ipsec LPLS (RAL/QUB/DCU)

O Meighan et al., Appl.Phys.Lett 70, 1497 (1997)

O Meighan et al., J.Phys.B:AMOP 33, 1159 (2000)

Summary - LP Continuum Light Sources

1. Table-top continuum light source now well established

2. Covers Deep-UV to soft X-ray spectral range

3. Pulse duration can be < 100 ps !

4. Continuum flux ~ 1014 photons/pulse/sr/nm (0.8J/10ns)

5. Low cost laboratory source - needs greater awareness

6. Recent work on (100 ps) + (6ns) Pre-plasma source - we already see a flux gain of up to X4 with Cu-A Murphy et al., Proc SPIE, 4876, 1202 (2003)

Problem of plasma debris for work in clean environments - proposals to solve, Michette, O’Sullivan, Attwood,…

Part II - Dual Laser Plasma Photoabsorption Experiments

Part II - Section A Photoabsorption Spectroscopy of Ions

Photoionization of Atomic Ions

Still a lot of work to be done here-

Nice review by John West in:

J.Phys.B:AMOP 34, R45 (2001)

Covers DLP Experiments & Merged Synchrotron + Ion Beams

No tuning requiredNo vapour required

Backlighting Plasma Io

Both Plasmas I = Ioe-nL

Isonuclear SequencesIsoelectronic Sequences

Relative Absorption Cross SectionNL =Ln(Io/I)

Dual Laser Plasma PrincipleFlexibleNeutral/Multiplycharged/Refractory Elements

x, T, I(W/cm2) Species choice

XUV DLP setup at DCU

XUV DLP Specifications

Time resolution: ~20 ns (LP Continuum duration)

Inter-plasma delay range: 0 - 10 sec

Delay time jitter: ± 1ns

Monochromator: McPherson™ 2.2m GI

X-VUV photon energy: 25 - 170 eV

Resolving power: ~2000 @25 eV (20m slits)

~1200 @ 170 eV

Detector: Galileo CEMA with PDA readout

Spatial resolution: ~250 m (H) x 250 m (V)

Kr-like ions

Mn ions

Some sample DLP case studies

Kr-like ions - Rb+, Sr2+, Y3+

DublinHave published upwards of 100 papers on DLP photoabsorption experiments on selected atoms and ions from all rows of the periodic table.

Motivation - almost always exploration of some 'quirk' of the photoionization process in a many electron atom !

Why Specifically Kr-like Ions ?

1. Prototypical high-Z closed shell atom - beyond simple Fano theory

2. 30+ years of research in both single and multiphoton ionization

3. Will the photoionization dynamics (q/) change (a little or a lot ?)

4. How will current many-electron photoionization theory stand up ?

Electronic Configuration4s24p6

XUV Photoabsorption along Isoelectronic (Kr-like) Sequence (Rostov/ DCU)

4s24p6 + hVUV 4s4p6np + 4s64p4nln’l’ Kr+(4s24p5) + ’lA Neogi et al., Phys.Rev.A 67, Art. No. 042707 (2003)P Yeates et al., J. Phys. B: At. Mol. Opt. Phys. 37, 4663 (2004)

It's a plasma with an ionization balance-how do we know that we have Y3+ say ?

4p - nd, Epstein and Reader , J. Opt. Soc. Am 72, 476 (1982)4s - 5p assigned using Clark et al., J. Opt. Soc. Am. B 3, 371 (1986)

What could theory tell us ?

Xn q-value

What about cross sections ?

'Mirroring Resonances'

2q2 0 complete cancellation - no resonances

An update from Aarhus ! Bizau, West & Kilbane (DCU)

Kr-like ions - Summary 1. It is clear that the ‘Fano’ profile parameters for the main 4s – np resonances in each spectrum are very sensitive to degree of ionization and that complex doubly excited resonances persist (at least in the early members of the isoelectronic sequence).

2. Computed cross sections show good agreement with measured spectra.

3. Rescaling the Coulomb interaction is needed to better fit the 4s-5p resonance in Sr2+

4. We observe that the complex doubly excited resonances straddling the first 4s-5p in Kr moves to higher photon energy blending with higher energy 4s-np (n>6) resonances and that the 4s-5p drops below the 4p threshold for Y3+

7. For Y3+ the resonance q values become quite large and the spectrum consists mainly of almost symmetric absorption features

8. We see that a number of features are suppressed in Rb+ and Sr2+ since they are built from exactly (or almost exactly) cancelling 'mirroring resonances'

DLP XUV Photoabsorption along isonuclear sequences - Mn2+ (and Mn3+) Ions

'duplicity of the 3d orbital' - "valence-like by energy but inner shell-like by radial distribution" (Dolmatov, JPB 29, L687 1996)

Mn2+, 3p63d5 + h 3p5(3d6 + 3d54s) Mn+, 3p63d54s + h 3p5(3d64s + 3d54s2)

3p-subshell photoabsorption - Mn2+

3p-subshell photoabsorption - Mn2+

Overall we see a good match withDolmatov at least at the low energyside of the main resonance

But why does the experimentaltrace fall off much more quicklythan the theory -

Excitation from metastable states ?

Metastables and their effect on 3p-subshell photoabsorption of iron group ions - Mn3+

Mn3+, 3p63d4 + h 3p5(3d5 + 3d44s)

Mn+

Mn2+

Mn3+

What do simple Cowan code calculations give ?

First StepCompute 'cross sections' for photoabsorption from ground and low-lying terms of Mn3+ (3d4) - 5D, 3P, 3F, 3G, and 3H

What do you get ?

Next StepTo 'reproduce' the experimental plasma spectrum, take a weighted sum over each such cross section

Vary the temperature and compare with expt.

Mn ions - Summary 1. Clear that we are going to have problems with excited state absorptionsince we have a hot sample. In fact the plasma temperature at will vary from ~10 eV at 20 ns to 2 eV at 150 ns and hence we will have significant populations of low lying 3dn and 3dn-14s states

3. Same is also true of the ion beams used in the synchtotron experiments

4. So we need a combined atomic physics and plasma physics approach -some codes available (HULLAC) but complex and expensive

5. Contrast with Kr-like ions - closed shell - stable - ions tend to converge and stay on this favoured configuration - nice to work with

6. Same problem will occur in 4d, 5d, 4f and 5f metals

7. However, electronic structure of Mn2+ and Mn3+ ions important in manganites (recent Nature papers), biology (DNA),.....

VUV Photoabsorption Imaging

Part II - Section B (short)

Collaboration between DCU & Univ. Padua

VUV Absorption Imaging Principle

Pass a collimated VUV beam through the plasma sample and measure the spatial distribution of the absorption. Convertto 'Equivalent Width' images and extract column density (NL)maps - see Rev.Sci. Instrum. 74, 2992 (2003) for details

Io(x,y,,t)

Sample

I(x,y,,t)

VUVCCD

€

I =I0e−σ n(l )dl∫

Hirsch et al, J.Appl.Phys. 88, 4953 (2000) - QUB/DCU Collaboration

VUV Photoaborption Imaging

Time resolution: ~10 ns (200 ps - EKSPLA)

Spectral range: 10 - 35 eV (120 - 35 nm)

VUV bandwidth: 0.025 eV@25 eV

(50m slits)

Spatial resolution: ~120 m (H) x 150 m (V)J Hirsch, E Kennedy, J T Costello, L Poletto & P Nicolosi Rev.Sci. Instrum. 74, 2992 (2003)

1. VUV light can probe the higher (electron) density regimes not accessible in visible absorption experiments

2. The refraction of the VUV beam in a plasma is reduced compared to visible light with deviation angles scaling as 2

3. Image analysis is not complicated by interference patterns since the VUVcontiuum source has a small coherence length

4. VUV light can be used to photoionize ions - simplified equation of radiative transfer (no bound states).

5. Fluorescence to electron emission branching ratio for inner shell transitions can be 10-4 or even smaller => almost all photons are converted to electrons

Advantages of using a VUV beam

VUV absorption Imaging- Ca+ - 33.2 eV3p64s (2S) - 3p54s3d (2P)

Plume Expansion Profile - Singly Charged Calcium & Barium Ions

Ca+ plasma plume velocityexperiment: 1.1 x 106 cms-1

simulation: 9 x 105 cms-1

Ba+ plasma plume velocityexperiment: 5.7 x 105 cms-1

simulation: 5.4 x 105 cms-1

Delay (ns)

Plu

me

CO

G P

ositi

on (

cm)

1. VUV light can probe the higher (electron) density regimes not accessible in visible absorption experiments

2. The refraction of the VUV beam in a plasma is reduced compared to visible light with deviation angles scaling as 2

3. Image analysis is not complicated by interference patterns since the VUVcontiuum source has a small coherence length

4. VUV light can be used to photoionize ions - simplified equation of radiative transfer (no bound states).

5. Fluorescence to electron emission branching ratio for inner shell transitions can be 10-4 or even smaller => almost all photons are converted to electrons

Advantages of using a VUV beam

What do we extract from I and Io images ?

€

A=log10(I0(x,y,t,λ)dλ∫I (x,y,t,λ)dλ∫ )Absorbance:

€

WE = [1−e−σ (λ)NL]∫

€

WE =Δλ[I0 −I ]dλ∫I 0dλ∫

⎛

⎝ ⎜

⎞

⎠ ⎟

EquivalentWidth:

d

You can also extracts maps of column density,e.g.,Singly Ionized Barium

Since we measure resonant photoionization, e.g.,

Ba+(5p66s 2S)+h Ba+*(5p56s6d 2P) Ba2+ (5p6 1S)+e-

h = 26.54 eV (46.7 nm) and

the ABSOLUTE VUV photoionization cross-section

for Ba+ has been measured:

Lyon et al., J.Phys.B 19, 4137 (1986)

We should be able to extract maps of column density -

'NL' = ∫n(l)dl

Maps of equivalent width of Ba+ using the 5p-6d resonance at 26.55 eV (46.7 nm)

dl

Convert from WE to NLCompute WE for a range of NL and fit a function f(NL) to a plot of NL .vs. WE

Apply pixel by pixel

€

WE = [1−e−σ (λ)NL]∫ d

Result - Column Density [NL] Maps

(A) 100 ns (B) 150 ns(C) 200 ns(D) 300 ns(E) 400 ns(F) 500 ns

VPIF - Provides pulsed, collimated and tuneable VUV beam for probing dynamic and static samples

Spectral (1000) & spatial (<100 m) resolution anddivergence (< 0.2 mrad) all in excellent agreement with ray tracing results

Extracted time and space resolved maps of column density for various time delays

Measured plume velocity profiles compare quite well with simple simulations based on adibatic expansion

VPIF - Summary

Space Resolved Thin Film VUV Transmission and Reflectance Spectroscopy - PVK

‘Colliding-Plasma’ Plume Imaging Non-Resonant Photoionization Imaging

VUV Projection Imaging ?

Photoion Spectroscopy of Ion Beams ?

Current & Future Applications

Photoionization Mass Spectrometry R Flesch et al., Rev.Sci.Instrum 71, 1319 (2000)

VUV Photoionization of O2

Laser on

Laser off

NGC 2346

NGC2346 - Planetary NebulaDistance - 2,000 light yearsExtent ~ 0.4 light years

Result of the collision of two stars - believed that one became a red giantand swallowed its partner in the binary system.

Credit: Hubble Wide Field & Planeary Camera - Massimo Stiavelli (NASA)

‘Colliding Stars Model System' - 'Colliding Plasmas'

Colliding Laser Plasma Generation

Laser Pulse Energy: 10 -150 mJ/ beamLaser Pulse duration: 12 - 15 nsFocal Spot Size: ~ 100 mIrradiance: 1010 - 1011 W.cm-2

Ca - Emission Imaging @ 423 nm

Tight point focus on each Ca face/ 120 mJ per beamStagnation for angled target geometry

How about hetero-atomic collisions ?- Li + Ca Plasmas

Should be able to track each plume species individually-so we could look for crossover at the stagnation layer

LiLaserBeam

TargetLensWedge

Ca

Li

Hetero-atomic collisions-Li+Ca Plasmas

Ca -420 nm

Ca+ -390 nm

Li+ -548 nm

Li -670 nm

Delay = 300 ns & Gate time = 50 ns3O wedge, ~ 10mm Plume - Plume Separation

'Collisionality Parameter'

Collisionality () will be determined by both the mean free path(ii) and colliding plasma experimental scale length' (L).

= D/ii = D/Cstii = D.ii/Cs

Expect to strong stagnation for counter streaming plasmas where the mfp is small in comparison to the ablation front separation - Rambo and Denavit, Phys. Plasmas 1 4050 (1994)

Cs= Ion sound speed,ii = ion-ion collision frequency

What have we learned to date ?Strong stagnation in table top colliding plasmasdue to large value of the collisionality parameter ()

Degree of confinement/ hardness of the stagnationlayer can be controlled by designing the value of

Stagnation layer becomes quite uniform after 100s nsand so looks attractive for investigation as alternativepulsed laser materials deposition source

For this reason it also looks a good bet for atomic physics experiments using laser probing/excitation.....

Part III - Next steps in fundamental photoionization studies ?

Atoms and Molecules in Laser Fields1. Attosecond pulse generation/ HHG

2. Photoionization of ‘state prepared’ species(a) Weak Optical + Weak X-VUV(b) Intense Optical + Weak (Intense) X-VUV

3. Atoms, Molecules, Cluster & Ions in Intense Fields

(Multiple-Photon and Optical Field/Tunnel-Ionization)

Free Electron Laser at Hasylab, DESY, Hamburg

'Laser-like' radiation in the VUV and EUV

Free electron radiation sources

Bending magnet, broad band

NW x bending magnet

NU2 x bending magnet

NU2 x Ne x bending magnet

NU , NW = # magnetic periods

Ne = # electrons in a bunch

1=u/22(1+K2/2)

Josef Feldhaus, DESY, Hamburg

Schematic layout of a SASE FEL

Experimental Hall

LINAC Tunnel

Timetable EUV FEL - TTF2February 2004: - complete linac vacuum

- install photon diagnostics in FEL tunnel

Mar.-July 2004: - injector commissioning- completion of LINAC

Aug.-Dec. 2004: - LINAC and FEL commissioning with short bunch trains- installation of first two FEL beamlines (~20 µm focus direct beam and high resolution PGM)

Jan.-March 2005: - commissioning of first FEL beamlines and gas ionisation monitor- photon beam diagnostics

Spring 2005: - first user experiments

Xe PES FEL (June 24th) -

Femtosecond X-VUV + IR Pump-Probe Facility,Hasylab, DESY

OPA

Pump-probe experiments in the gas phase (project: II-02-037-FEL)

Participating groups:HASYLAB, Hamburg, GermanyJ. Feldhaus, S. Dusterer, R. Treusch, Kai Tiedke, Elke Ploenjes

LIXAM, Orsay, France M. Meyer, D. Cubannes

NCPST, Dublin City University, Ireland J. T. Costello, Philip Orr (QUB), P Yeates

M. Meyer et al, LIXAM, Orsay, France

Two subsets of experiments

II-ADirect photoionization in a non-resonant laser field

II-BResonant photoionization in a resonant laser field

Let's first look at II-A -

‘Direct photoionization' in a non-resonant laser field*

*Slides provided by Patrick O’Keefe and Michael Meyer,

Ponderomotive streaking of the ionization potential as a method for measuring pulse durations in the XUV domain with fs resolution

E.S. Toma, H.G. Muller, P.M. Paul, P. Berger, M. Cheret, P. Agostini, C. LeBlanc, G. Mullot, G. CheriauxPhys. Rev. A 62, Art. No. 061801 (2000)

Ar 3p6

Ar+ 3p5

VUV

IRe-presence of IR:- shift of IP- broadening of PES peaks- sidebands

Test-experiments at LLC: M. Meyer, P. O’Keefe (LURE), A. L’Huillier (LLC)fs-laser system: Ti:Saph. 800 nm, 50 fs, 1 kHz

VUV --> HHG, T ≈ 30 fs, 1 kHz, IR --> up to 0.5 mJ --> 1-10 TW/cm2

PES: magnetic bottle spectrometer- high angular acceptance- high energy resolution for Ekin < 10 eV

Tfs

Ar 3p6

Ar+ 3p5

VUV

IR

e-

Cross correlation experiments using high order harmonics

E = 15.8 eV

-50

0

50

H21H19H17H15H13 H23

5 10 15 20

Ekin (eV)

Generation(HHG)

(laser) = 800nm H11 = 17 eV H13 = 20 eV H15 = 23 eV

: :

But also very interesting are:

Type IIB-Experiments-

'Resonant photoionization' in an intense/resonant fields

=>Study intensity controlled autoionization !!

Proposed (approved) experiment at the FEL

Exp.: Two-photon double-resonant excitation FEL : h = 65.1 eV (tunable) Laser : = 750 - 800 nm (tunable)

Coupling of He Doubly Excited States

He 1s2

2s2p

2s3d

Intense Laser

VUV

20 fs (34 meV)

A. I. Magunov, I. Rotter and S. I. StrakhovaJ. Phys. B32, 1489 (1999)

H. Bachau, Lambropoulos and ShakeshaftPRA 34, 4785 (1986)

2s2p 1P – 2s3d 1D

Bachau, Lambropoulos and Shakeshaft, PRA 34, 4785 (1986)

Laser on Resonance (2 = 0)& scan the XUV photon energy

1s2(1S) + hXUV -{2s2p (1P) + hLaser

<=> 2s3d (1D)}

Could this be done with a laser plasma X-VUV source

and a table top OPA ?

In principle YESYou just cross the sample with intense laser (OPA) and weak XUV beams

Need wavelength selection and high (average) X-VUV intensity

Count rate low - ~ 1 ion/laser shot for He with Volint ~ 10 -3 cm-3

Answer

But - the Ca+ 3p-subshell resonances have:1. Cross sections up to 2500 MB .vs. < 0.1MB for He2. Excitation widths up to 100 meV3. A VUV excitation energy (31 eV)

0

500

1000

1500

2000

2500

28 29 30 31 32 33 34

Ca+. ALS Measurement. 5 meV per point.

SigRaw (MB)

Photon Energy (eV)

Scheme- Ca+:

3p64s (2S) + hXUV (33.2 eV)

{3p53d4s (2P) + hLaser (3 eV) <=> 3p53d5p (2D)}

Exploratory study in DCU - Summer 2005

Scheme- Ca+:

Photoionization SummarySingle VUV - X-ray photon photoionization (and concomitant correlation) in atoms and ions is still a rich source of physics

Photoionization of atoms (much less so ions) in intense IR/VIS laser fields is now well established also (MPI .vs. Tunnelling)

New things to so - Cross-over of the above two ?Atoms in intense VUV/XUV (high frequency) fields - first result - Nature 2002

Resonant/ non-resonant photoionization of atoms in intenseresonant/non-resonant laser fields

Why bother ? Pushing limits - exploring new spaces - new science & technol.

Ideas that come to mind at this workshop

FEL Opportunities1. PIFS on weak resonances2. PIFS on ion beams - Kr-like ions

DLP1. Exploring Xe-like, 5s-subshell excitation

Table Top PIFS1. PIFS with laser plasma source2. Or with tuneable (upconverted) VUV