Cheiron School, SPring-8, Japan
October 2, 2014

Studies on atoms and molecules
using synchrotron radiationand free electron lasers
Kiyoshi Ueda
Institute of multidisciplinary research for advanced materials
Tohoku University, Sendai 980-8577, Japan

Introduction of myself

Prof. Kiyoshi Uedaat
Tohoku University （Sendai）
Institute of multidisciplinary research
for advanced materials
Leadinga research group for electron andmolecular dynamics

Atomic and molecular science using
Synchrotron Radiation
Ueda, JPB 36, R1 (2003);
Ueda & Eland, JPB 38, S839 (2005);
Ueda, JPSJ 75, 032001 (2006);
Kabachnik et al. PR 451, 155 (2007).
Application of the SR-based
experimental techniques to laser
experiments(femtosecond laser and FEL)

Outline
1. Introduction to quantum world
2. Atomic resonant photoemission spectroscopy- Introduction to the quantum interference
3. Vibrationally-resolved core-level photoelectron spectroscopy- Adiabatic approximation and Franck-Condon analysis- Young’s double-slit experiments
4. Multiple-ion momentum imaging- Snapshots of molecular deformation within a few fs
5. Electron-ion momentum imaging- Molecular-frame photoelectron angular distributions
6. Interatomic Coulombic decay
7. Characteristic properties of free electron lasers
8. Atomic multi-photon processes by FEL: from EUV to X

Photoelectric effect
When matter is shined by the light, electron isemitted from the surface.
(i) Frequency of the light needs to be larger than n0.
(ii) Kinetic energy of the electron is determined by thefrequency of the light.
(iii) Number of electrons is proportional to the intensityof the light.

Einstein’s explanation
Light at frequency of n is considered to be a group ofparticles (photons) and each photon has energy hn.
An electron gets the energy hn when it absorb one
photon.
The electron in the matter is bound. For the electron
to be emitted from the matter, the electron needs toreceive the energy more than the work function W.
Then the kinetic energy KE of the emitted electron canbe given as KE = hn – W.

Photoelectron spectroscopy (UPS, XPS)
Precision measurements for kinetic energies of photoelectrons
emitted via Einstein’s photoelectric effects
Kinetic
energyPhotoelectron
spectrum

Vacuum level
Intensity
Valence level

BindingenergyBalmer and Rydberg formulae

Balmer found beautiful regularity in the H spectrum!

n

1 
 1
Rydberg formula： c    R 2  2 
n' 
n
1

c, speed of light; λ, wavelength; R, Rydberg constant (R =109737.309 cm-1)

Bohr’s atomic model
Electron orbits exist only when the classical orbits satisfy thefollowing condition of quantization:2 p d  nh
0

, angle of rotation; p= mer2d/dt , angular momentum; r, radius; me, electron mass

The electron binding energies are discrete:
Ēn= -hcR/n2

De Broglie’s matter wave and Bohr’s model

Quantization： h/p2

 p d  nh
02rn = n = nh/p = nh/mv

Schrödinger equation of H atom (in atomic units)HΨ(r) = EΨ(r)H  T  U (r )Hamiltonian

p2
1 2
T

2
2
2 r

kinetic energy


pi
r

momentum1
U (r)  rpotential energy

1En   22n

Ψ: wave function
complex number (with phase!)Atomic and molecular science now
Target: single atom or molecule; size: ~ 1 Å (= 0.1 nm = 10-10 m)

How to use synchrotron radiation to study atoms and molecules
We use monochromatic synchrotron radiation to excite atoms
and molecules and to study their electronic structures as wellas electron and nuclear dynamics in the excited states.
A single photon should be absorbed by a single atom ormolecule first!

What photon energies to be used
Electron binding energies (eV)

Vacuum ultraviolet light!

The experiments need
to be in the vacuum!
SR

Ion
detector

Mol. Beam

The easiest experiment:
ion yield spectroscopySPring-8 BL27SU
Figure-8 undulator
Linearly polarized light
Horizontal polarization (1st)Vertical polarization (0.5th)
T. Tanaka and H. Kitamura, J. Synchrotron Radiation 3, 47 (1996).

Soft X-ray monochromator
Hettrick type: varied line spacing plane grating
Energy range

0.15 ~ 2.5 keV

Photon Flux

> 1011 photon/s

Energy resolution

10000 - 20000

H. Ohashi, Y. Tamenori, E. Ishiguro et al. Nucl. Instr. Methods A 467, 533 (2001).

Ne 1s total ion yield spectrum
np Rydberg series- Ēn = IP – En = R/(n-μ)2
μ : quantum defect R =13.6 eV

IP

S

sn
s = sdir++ s1s e  (hn-En)/(Gn/2)21+ennsn  1 /( n   )3
Γn= const!

Auger decay and Auger electron spectroscopy
photoelectronCore hole lifetime
defines the line width!

Auger electron

SES2002 analyzer•

Electrostatic hemisphericalanalyzer– Mean radius 200 mm– E/PE=1/1600(66 meV at pass 100 eV)– MCP+CCD cameraor MCP+Delay line anode– Gas cell system
or Doppler-free molecular beamsourceUeda et al. PRL . 90, 153005(2003)
or effusive beam + momentum
resolved ion spectrometer
Prümper et al. PRA 71, 052704,(2005).

Angle-resolved resonant Auger spectra of Ne at
1s -> 3p excitation

2p-2(1D2)3p

P2 (cos )  [3 cos  1] / 2
b: asymmetry parameter
Measured angular distributions tell us how theangular momenta are coupled in the atom ,allowing us the spectroscopic assignment !

Resonant Auger spectra of Ne “between”
1s -> 3p and 1s -> 4p excitationss  I (0)  2  I (90)2p-2(1D2)3p

Interference effects between the two paths
Aa = da+sa = |Aa |2

Sn

Dna
i+en

en  (hn-En)/(Gn/2)
da = <g|r|a>
Dna = <g|r|in><in|v|a>
|i>

|a>

Dna
da
|g>

De Fanis et al. Phys. Rev. Lett. 89, 023006 (2002).

Sendai City

Statue of Load Date

Jozenji Street

Introduction of molecular worldH( R, r )  E( R, r )2TR   
2 k M k Rk2

KE of nucleus

H  H 0  TR

H  TR  Tr  V (r, R)2Tr  

2m j rj2

KE of electrons

H 0  Tr  V (r , R)

[ H 0  e n ( R)] ( R, r )  0
e n (R ) : adiabatic potential energy ( R, r )    n ( R)n ( R, r )n[TR  e m ( R)] ( R)  E  ( R)
0
mv

0
mv

0
mv

Nuclear motion is within the adiabatic potential energy surface!

Born-Oppenheimer approximation

Franck-Condon approximation for photoionizations iv ' ( E ) ~|  X iv* ' ( R) DE ( R) X 0 ( R)dR |2

X iv* ' ( R), X 0 ( R) : Vibrational wavefunctions of ionic iv’ and ground 0 states

DE ( R )    E* ( r, R )r core ( r, R )dr

 E ( r, R),core ( r, R) : Electronic wavefunctions of the continuum E and core orbitals
Assume that the dipole moment DE(R) does not depend on Rs ( E ) ~| DE ( Re ) | F (v'0)

iv '

2

F (v'0) |  X iv* ' ( R ) X 0 ( R )dR |2 Franck-Condon factor
Vibrational intensity distribution in the photoelectron
spectrum is determined by the Franck-Condon factors

Franck-Condon analysis based on harmonic approximation
Linear coupling model
Intensityn‘ = 2

F (1,0) 

Ionic staten‘ = 1a ( R )22

 a ( R )2 
exp  2 

a  n‘  0R

Photoelectron
spectrumElectronic
ground state

n=0
R0

R'0

 a ( R )2 
F (0,0)  exp  2 
F (1,0) a ( R)F (0,0)2

2

Internuclear distanceOne can extract R from photoelectron spectroscopy!

Franck-Condon analysis for the vibrational structureof the C 1s and O 1s mainlines of CO
I ~|<y+v|y0>|2 : FC factor
y0: v=0 vibrational wave functionin the ground statey + v: v-th vibrational wave functionin the core-ionized state
Stable geometry of the core-ionized state
extracted from the vibrational structure
Exper.

TheoryC 1s-1
Re (Å) -0.051 (1)-0.051O 1s-1
Re (Å) 0.037(2)0.028Matsumoto et al. Chem. Phys. Lett. 417, 89-93 (2006).

Satellite spectrum in core-level photoemission in CO

HOMO-LUMO*

Mainline

Ehara et al. J. Chem. Phys. 125, 114304 (2006).

Franck-Condon analysis of the vibrational structure in
the symmetry-resolved C 1s satellite bands of CO

Solid lines: measured
symmetry resolved
spectraVertical bars: ab initio
FC factors

Ab initio potential curves

Ab initio FC factors reproduce themeasured vibrational distributions.
Ueda et al., Phys. Rev. Lett. 94, 243004 (2005).

N(1)Evidence of the dualityof waves and particles!

N(2)Electrons also showinterference fringes!

Evidence that the light is the wave!

Franck-Condon analysis for the vibrational structureof the N 1s 1su and 1sg mainlines of N2
2500

hn=500 eV

1500
1000
500
0

90.0

90.5

91.0

Kinetic energy (eV)

(1su)
-1
(1sg)
-1

Relative intensity

Counts2000

N2 N 1s

SAC-CI
v’=0

Exper.

v’=1
90.0

90.5

Equilibrium geometries of the core-ionizedstates extracted from the vibrational structure

91.0

Kinetic energy (eV)N 1su-1
Re (Å) -0.023(1)N 1sg-1
Re (Å) -0.018(1)Theory-0.021-0.017

Ehara et al. JCP 124, 124311 (2006)

Cohen-Fano two-center interference
Two 1s ortibals in N2 correspond to Young’s double slits.
Molecular core-level ortibals:
Core-level photoemission from fixed-in-space N2:

Two center photoelectron wave

Interference fringe

where k: photoelectron momentum; R1,R2: position vectors of N (1) and N(2)Orientational average: Cohen-Fano formulaInterference oscillatory structure becomes much smaller but remains!
H.D. Cohen and U. Fano, Phys. Rev. 150, 30 (1966).

Ab initio N 1s 1su and 1sg photoionization cross sections of N2

Oscillation:
Two-center Interference
Cohen-Fano prediction !

Semenov et al., J. Phys. B: At. Mol. Opt. Phys. 39, L261 (2006)

sg /su ratio: experiment vs ab initio and Cohen-Fano
2.2

Cross section ratio sg/su

2.0

N2 K shell/
Experiment
Original Cohen-Fano
RPA

1.8
1.6
1.4
1.2
1.0
0.8
0.6
1

2

3

4

5

6

Electron momentum (a.u.)
Both experimental and ab initio interference fringes shift from the prediction
by Cohen-Fano formula!
Liu et al., J. Phys. B. 39, 4801-4817 (2006); JESRP 156-158, 73-77 (2007).

Photoelectron scattering by the neighboring N atom
The amplitude of the photoelectron wave from one center:y2  A2B2

A1

B1

The amplitude of the photoelectron wave from two centers: y1  y2

Cohen-Fano interference
A1A2 interference term
N(1)

N(2)

N(1)

N(2)

The cross section~ |y1  y2 |2  |(A1B1) (A2B2) |2

0

A1B1 and A2B2 one-center interference terms

d1(k): scattering phase
CF A1A2 interference term

A1B2 and A2B1 two-center interference terms !

Sendaiin summer

Tanabata festival

Multiple-ion coincidence imaging setup
E field

Y Ion 2D

field free
TOF tubehn electron
MCP

PSD
x2y2t2
x1y1t1t0

t, Z 80mm

x4y4t4X
x3y3t3supersonic jet

25

70skimmer

140 mmSample gas jet

position & time of flight (x,y,t)

3D momentum of each particle

How to obtain 3D momentum

t: ion time-of-flight6

to: ion TOF at rest

TOF of 2nd ion (s)24m(x  x0 )m( y  y0 )px , py 
, pz  qE (t  t0 )ttx, y: arrival position on the detector.
x0, y0 : initial position of the ion
m : ion mass

q: ion charge

O+ + CO+C+ + O+

E: electric field in the acceleration region
2

4

TOF of 1st ion (s)

To be exact Pz becomes nonlinear

Iterative procedure6

Total electron yield spectrum of CO2 in the C1s excitation region
CO2 ground state configuration:
1sg21su22sg23sg22su24sg2
O1s

C1s

O2s

C2s

3su21u41g4(1Sg+); 2u05sg04su0
2u ← 2sg resonanceIntensity (arb. units)

*

TIY

297.63 eV
C K-edge4su ← 2ss
shaperesonance
shaperesonanceu g-

2e exc.

290

295

300

305

310

Photon energy (eV)

315

320

325

O

Renner-Teller splitting of CO2

C

Out-of-plane 2u: B1E

CO2 C1s-1 2uO
Bending plane ⊥ E

In-plane 2u : A1

OO

CO2 Ground stateFranck-Condon
regionE

C
Bending plane // E

CO23+ -> C+ + O+ + O+
180º
Bond angleSnapshot of the bending motion in the core-exited statewith a liftetime ~7 fs
Newton DiagramOut-of-plane 2u: B1
LinearIn-plane 2u : A1

Bent

Muramatsu et al. Phys. Rev. Lett. 88, 133002 (2002).

Electron-ion coincidence momentum imaging
Multihit 2D detector

Multihit 2D detector
Electric field

Y

Y

N+
B
e-

B+
e- N
O+
A

O+
A

X

X
X-raysMagnetic field

Ion-ion coincidence

Molecular axis

Ion momentum conservation

Retrieval of the source point

Electron-ion-ion coincidence

Molecular-frame e- angular distribution

Towards photoelectron diffraction measurement

Total electron yield spectrum of CO2 in the C1s ionization region

4su ← 2sg shape resonance
CO2 ground state configuration:
1sg21su22sg23sg22su24sg2
O1s

C1s

O2s

C2s

3su21u41g4(1Sg+); 2u05sg04su0
C 1s threshold
297.63 eV

N. Saito et al., J. Phys. B, 36 L25 (2003).

Reaction plane
Reaction plane ＝plane define by the E vector and molecular axise-Electric vector

Electron emission
direction

O

n
C

O
Molecular axis

We focus on the electron emission within this reaction planeC1s photoelectron diffraction (MFPAD) of CO2:
comparison between experiment and theory
Photon energy

Shaperesonance

The general agreement between experiment and theory is reasonable.
At the shape resonance, the intensity drops at  n  90  i.e. S-S paralleltransition. The intensity drops at   90  , i.e., su photoelectron wave !

Near Sendai

Motsu-jiMatsushima bay

Mount Zao

Chuson-jiAuger vs Interatomic Coulombic Decay (ICD)

Ne

Intra-atomic

high-energy Auger e-

Energy transfer via
virtual photon exchange

low-energy ICD e-

ICD rate is R dependent!

Why is ICD important?
ICD: electronic decay where the environment plays a role!
ICD takes place in van der Waals clusters, in hydrogen bonding clusters, inmetallofullerenes, in bio-molecules in the living cell, etc
ICD is everywhere!
ICD is one of the key players in energy and charge transfer in these systems.

Metal atom in C60

Interatomic Coulombic Decay (ICD)
TheoreticalFirst prediction - HF cluster:
L.S. Cederbaum, J. Zobeley, and F. Tarantelli, Phys. Rev. Lett. 79, 4778 (1997).
Prediction - Ne dimer:
R. Santra, J. Zobeley, L.S. Cederbaum et al., Phys. Rev. Lett. 85, 4490 (2000).

Experimental
First observation - Ne cluster:U. Hergenhahn and coworkers, Phys.Rev. Lett. 90, 203401 (2003).
Cluster-size-dependent lifetime:
G. Öhrwall et al., Phys. Rev. Lett. 93, 173401 (2004).

Ne2 e-ion-ion coincidence:
R. Dörner and coworkers, Phys. Rev. Lett. 93, 163401 (2004).

ICD after Auger decay in a rare-gas dimer
X-ray

Ne

2p

core electronHigh energy
Auger electron

2s1s
Coulomb
interaction

Ne

Auger decay

ICD electron
Low energy（ICD; Interatomic Coulombic Decay）

If an atom has an inner-valence hole,
the adjacent atom may be ionized via ICD
R. Santra and L. S. Cederbaum, Phys. Rev. Lett. 90, 153401 (2003).

Why is ICD after Auger decay important?
Radiation damage caused in bio-molecules in the living cell
Radiation damage, caused by e.g., X-ray radiation, is initiated by coreionization.
Radiation damage is known to be caused by low energy electron collisions,
not high energy Auger electrons.
ICD is one of the important mechanisms to produce low energy electrons
after Auger decay!

Prediction of ICD after ICD Auger decay in Ne2
R. Santra and L.S. Cederbaum, PRL 90, 153401 (2003).

Prediction of ICD after resonant after Auger decay in ArKr
K. Gokhberg, P. Koloren, A. I. Kuleff & L.S. Cederbaum, submitted

Controlling electron emission and thus radiation damagesite specifically => principle of radiation therapy

First experiment of interatomic Coulombic decay after
Auger decay in Ar2(a) Core photoionization and Auger decay

2p ionization

Auger(b) Interatomic Coulombic decay
ICD electron
virtual photon

SPring-8 view from sky

ICD(c) Fragmentation

Ar2+

Ar+

Y. Morishita, X.-J. Liu, N. Saito, T. Lischke,
M. Kato, G. Pruemper, M. Oura, H. Yamaoka,
J. Harries, Y. Tamenori, I.H. Suzuki, and K. Ueda
Phys. Rev. Lett. 96, 243402 (1)-(4) (2006)
K. Ueda et al. JESRP 155, 113-118 (2007)

fragmentation

ArKr

We detect ICD electrons in coincidence with Ar+ andAr2+using e-i-i coincidence momentum spectroscopy

Y. Morishita et al. J. Phys. B 41, 025101 (2008)
K. Ueda et al. JESRP 166-167, 3 (2008)

Interatomic Coulombic decay after Auger decay in Ne2
Ne+＋

1s photo-e

Ne

BESSY

Auger
Ne+＋

Ne＋

ICD

K. Kreidi, T. Jahnke, …… , R. Doener
X.J. Liu, Y. Morishita, …, K. Ueda
J. Phys. B. 41, 101002 (2008)
Phys. Rev. A 78, 043422 (2008)
Phys. Rev. Lett. 103, 033001 (2009)

Ne++

Ne+

J. Phys.: Conf. Ser. 212, 012007 (2010)

fragmentation
We detect ICD electrons in coincidence with Ne+ andNe2+using e-i-i coincidence momentum spectroscopy

Phys. Rev. A 85, 043421 (2012)

ICD after Ne 1s Auger decay in NeAr

Ne 1s photoionization
photoelectron

Auger decay
Auger electron

ICD
ICD electronSoft X-ray

Ne+ Ar

Ne2+ Ar

Ne2+ Ar+hν = 889 eV(the atomic Ne 1s ionization threshold: 870 eV)
50

Ion–ion coincidence TOF map
Homodimers (Ne-Ne, Ar-Ar)
and heterodimers (Ne-Ar) areproduced.

Ne+-Ar2+

We can distinguish target
dimers from others by using
momentum conservation law.
TOF of the second ion (s)

Ne+-Ne+65Ne2+-Ar+

4
3
2
1

2

3

4

5

TOF of the first ion (s)

Ne2+-Ar+ -electron coincidence events
Ne2+-Ar+ coincident
Electron spectrum

(a)

(b)

Ph.V. Demekhin et al., J. Chem. Phys. 131, 104303 (2009)
T. Ouchi, K. Sakai et al., Phys. Rev. A, 80, 053415 (2011)

Ne 1s
photoelectron

Sum of the kinetic energiesof the two fragment ions
(KER; Kinetic Energy Release)

q2

q1
E1
Distributionof KERE2

R
KER  E1  E2 

1

qq
 1 2
4e 0
R

(Coulomb law)

(a)

(b)

KER peak ~ 8.2 eV
R = 3.5 ÅThis distance coincides with theequilibrium distance of the neutral
ground state of NeAr.

(a) ICD
Ne2+(2s-12p-1 3P)–Ar Ne2+(2p-2 3P)–Ar+(3p-1)(b) ICD
Ne2+(2s-12p-1 1P)–Ar Ne2+(2p-2 1D)–Ar+(3p-1)

52

Extraction of the ICD lifetime from line shape(a)(b)
120 fs
75 fs
30 fs

A long tail of Peak (b)comes from nuclear
dynamics within ICD
lifetime !

ICD lifetime of ~75 fs has
been determined for the
first time!

T. Ouchi, K. Sakai et al., Phys. Rev. A, 80, 053415 (2011).

Energy level diagram‘direct’ ICD
Photoelectron~19 eV Auger electron~780 eVICD electron + KER

photo ionization

Ne+(1s-1)~16.9 eV (b)Ne2+(2s-12p-1 1P)~9.6 eV(a)

Ne2+(2s-12p-1 3P)

Ne2+(2p-2 1D) + Ar+(3p-1 2P)‘exchange’ ICD

Ne2+(2p-2 3P) + Ar+(3p-1 2P)

Spin is flipped

Ne+ Ar

Ne2+ Ar

Kreidi et al. J. Phys. B. 41, 101002 (2008)

Ne2+

Ar+

ICD after resonant Auger decay(1) Resonant excitation(2) Resonant Auger decay
High energy
Auger- electroneSoft X-ray
Promotion of an inner-shell electron
to the unoccupied orbital(3) ICD+

Coulomb
interactionLow
e- energy
ICDelectron

Ionization of the adjacent atom via ICD

Creation of an inner-valence hole(4) Coulomb explosion++

Dissociation via Coulomb repulsion

We detect ICD electrons in coincidence with two singly-charged ions.
Theory: Kirill Gokhberg, Premysl Koloren, Alexander I. Kuleff & Lorenz S. Cederbaum (submitted)

Photo-excitation energies
Total ion yield spectrum
2p1/2-1 4s

Ion counts

4000

2p3/2

-1 4s

3d
3d

4d 5d 6d

4d 5d 6d
■

■

3000
2000
1000
244

246

248

Photon energy (eV)Ar 2p3/2 → 4s : 244 eV
Ar 2p3/2 → 3d : 247 eV

250

Ar+-Kr+ - electron coincidence events at Ar 2p → 4s excitation
Electron spectrum coincident with Ar+-Kr+~0.5 eVCounts

2.5 eV

Ar+-Kr+ KER
distribution

KER (eV)(A)
KER = 3.7 eV ( R = 3.9 Å )(B)Electron energy (eV)Counts(A) KER = 3.7 eV <> electron energy ~ 0.5 eV(B) KER = 3.7 eV <> electron energy ~ 2.5 eVBoth ICDs take place at R = ~3.9 Å(equilibrium bond length)

ICD after Ar 2p → 4s excitation in ArKr [244 eV](A)

Intensity distribution along KER + electron energy

Energies are calculated as
E = Auger final state energy- Ar+(3p-1)Kr+(4p-1) ICD final state energyCounts(B)

Estimated via
Auger data

Intensities are estimated frombranching ratios of Auger transitions

Intensity(arb. units)― estimate--- Gauss convolution(A)(B)
Energy (eV)Energy(eV)
4 1 3
2
3p ( D/ P)3d D
4.16
4 1
2
3p ( D)4s D
4.42
4 1
2
3p ( S)4s S
6.46
Auger final state

Intensity
(%)
46
12

[2] M. Meyer, et al., Phys. Rev. A, 49 3685 (1994).

ICD is closed(A) Ar+ (3p-2(1D/3P)3d 2D), 3p-2(1D)4s 2D), –Kr → Ar+ (3p-1)-Kr + (4p-1)(B) Ar+ (3p-2(1S)4s 2S)–Kr → Ar+ (3p-1)-Kr + (4p-1)
ICD may take place at ~60 % probability….

Ar+-Kr+ - electron coincidence events at Ar 2p → 3d excitation
Electron spectrum coincident with Ar+-Kr+

Counts~ 0.5 eV
~3.5 eV ~5.0 eV

Ar+-Kr+ KER
distribution(E)(C)
KER (eV)

KER = 5.0 eV ( R = 2.9 Å )KER = 3.7eV ( R = 3.9 Å )(D)Electron energy (eV)Counts(C) KER = 3.7 eV <> electron energy: ~ 0.5 eV(D) KER = 3.7 eV <> electron energy : ~ 3.5 eV
ICD takes place at R = ~3.9 Å (equilibrium bond length)(E) KER = 5.0 eV <> electron energy : ~ 5 eV
ICD takes place at R = ~2.9 Å (Van-der Waals wall)

ICD after Ar 2p → 3d excitation in ArKr [247 eV]

Intensity (arb. units)

CountsIntensity distribution along KER + electron energy(D) 7.1 eV(E) 10.1 eV(C) 4.3 eV

Estimated via
Auger data

Energies are calculated as
E = Auger final state energy- Ar+(3p-1)Kr+(4p-1) ICD final state energy
Intensities are estimated frombranching ratios of Auger transitions― estimate--- Gauss convolution

Energy (eV)ICDへのチャンネルが閉じている

Auger final state

Energy Intensity
(eV)
(%)

3p-2(3P)3d(C) 4P + 2F + 2D +4s 2D 3.96
(D) 3p4(1D)3d 2D + 2P 6.88
4(1D)4d(E) 3p10.08
2G + 2P + 2D + 2F

3.01

24.08
24.91

[3] M. Meyer et al., Phys. Rev. A 43, 177 (1991).

(C) Ar+ (3p-2(3P)3d 4P + 2F + 2D + 4s 2P )-Kr → Ar+ (3p-1)-Kr + (4p-1)(D) Ar+ (3p-2(1D)3d 2D)–Kr → Ar+ (3p-1)-Kr + (4p-1)(E) Ar+ (3p-2(1D)4d 2D)–Kr → Ar+ (3p-1)-Kr + (4p-1)
ICD may take place at ~97 % probability….

ICD after Ar 2p → 3d excitation in Ar2 [247 eV]ICD electron energy spectra
Experiment244 eV(4s exci.)

Counts

600
400
200
0
400

Counts

Theory247 eV(3d exci.)

300
200
100
0
0

2

4

6

8

10

Electron energy (eV)Resonant-Auger-induced ICD

Gokhberg et al.

One can generate low-energy electron site specifically.

One can control the energy of electrons via photo-excitation energy.
One can control the radiation damage site specifically (radiation therapy!)

Heidelberg U. ICD gangs in Germany and Japan ! AIST

Alex

Lenz

Spas

Yuichiro

Norio

Frankfurt U.

Reinhard

Markus

Kathi

Till

HIroshi

Kyoto U.

Tohoku U.

Hironobu

KentaroGeorg

Xiao-Jing

Kiyonobu

EUV-X FELs in the world
LCLS in operation
2009
since2009

SCSS test accelerator in operation
since 2008

SACLA in operation since March 2012

Swiss FEL (2017), Korean FEL,
Shanghai FEL, etc., are coming!

FLASH in operation since 2005
FERMI starts operation in December 2012!

European XFEL starts operation in 2016?

Single-shot X-ray imaging by XFEL
BeforeDuring ~10 fs

After ~50 fs

Coulomb explosion

Needs more photons….

Radiation damage….

R. Nertze et al., Nature 406, 752 (2000).

Serial femtosecond x-ray crystallography: phasing
Femtosecond X-ray Protein
Nanocrystallography ,Chapman et al.,Nature 470, 73–77 (2011).
High-Resolution Protein Structure
Determination by Serial
Femtosecond Crystallography,
Boutet et al. Science 337, 362 (2012).
Natively Inhibited Trypanosoma
brucei Cathepsin B Structure
Determined by Using an X-ray Laser,
Redecke et al. Science 339, 227 (2013).

Phasing of the serial femtosecond x-ray crystallography has been dependent on
molecular replacements…
If the structure is completely unknown, phasing approaches make use of anomalous
dispersion in the scattering signals from specific heavy atoms.
Multi-wavelength anomalous diffraction at high X-ray intensity
S.-K. Son, H. N. Chapman, and R. Santra, Phys. Rev. Lett. 107, 218102 (2011).
However…..
De novo protein crystal structure determination from X-ray free-electron laser data
T.R.M. Barends et al., Nature (2013) doi:10.1038/nature12773
Conventional phasing method based on anomalous dispersion worked !

Characteristic properties of FEL pulses
Intense1014 W/cm2 (EUV) - 1020 W/cm2 (X)One LCLS pulse
at 2 keV canremove all ten
electrons fromthe neon atom.

Femtosecond electronic response of
atoms to ultra-intense x-rays
L. Young et al., Nature 466, 56 (2010).

The pulse is so
intense that it
causes electronic
damage to thesample.

Non-linear X-ray atomic Physics
Ultra-Efficient Ionization of Heavy Atoms by Intense X-Rays
B. Rudek, S-K. Son, L. M. Foucar, S. W. Epp,
B. Erk, R. Hartmann, M. Adolph, R.
Andritschke, A. Aquila, N. Berrah, C. Bostedt,
J. Bozek, N. Coppola, F. Filsinger, H. Gorke,
T. Gorkhover, H. Graafsma, L. Gumprecht, A.
Hartmann, G. Hauser, S. Herrmann, H.
Hirsemann, P. Holl, A. Hömke, L. Journel,
C.Kaiser, N. Kimmel, F. Krasniqi, K-U. Kühnel,
M. Matysek, M. Messerschmidt, D. Miesner, T.
Möller, R. Moshammer, K/ Nagaya,
B.Nielsson, G. Potdevin, D. Pietschner, C.
Reich, D. Rupp, R.Santra, G. Schaller, I.
Schlichting, C. Schmidt, F. Schopper, S.
Schorb, C-D. Schröter, J. Schulz, M. Simon,
H. Soltau, L. Strüder, K. Ueda, G.
Weidenspointner, J. Ullrich, A. Rudenko, and
D. Rolles
Nature Photonics Nature Photonics 6, 858 (2012).

Characteristic properties of FEL pulses
ultra-short (10 – 1 fs)
Attosecond dynamics

0 – 0.5 fs

Femtosecond dynamics

Mili-second mechanics

0 – 10 ps

0 – 200 ms

Courtesy of Simone Techert

Characteristic properties of FEL pulses
ultra-short (10 – 1 fs)
Attosecond dynamics

0 – 0.5 fs

Femtosecond dynamics

Mili-second mechanics

0 – 10 ps

0 – 200 ms

Catching atomic motion and electron (hole)wave-packet in reaction(molecular vs electron movie)

SACLA XFEL (lased on 7 June 2011)

on air!

SCSS test accelerator : EUV-FEL (20-24 eV)
Momentum or velocity
imaging apparatus￥

EUV-FELMultiple ionization of rare gas atoms and clusters: with M. Yao’s group
VMI: with help of M. Vrakking’s group
Autocorrelation: with J. Ullrich’s group

Multi-photon ionization of atoms● Second-order autocorrelation of SCSS EUVFEL pulses via timeresolved two-photon single ionization of He– Characteristics of SASE-FEL● Photoelectron angular distributions for two-photon Ionization of He

atoms by SCSS EUVFEL pulses– Potential of coherent control via seeded FEL● Deep inner-shell multi-photon absorption of Ar and Xe atoms by

SACLA XFEL pulses– Relevance to the electronic radiation damage

Second-order autocorrelation of EUV FEL pulses via
time resolved two-photon single ionization of He
R. Moshammer, Th. Pfeifer, A. Rudenko, Y.H. Jiang, L. Foucar, M. Kurka, K.U. Kuhnel,
C.D. Schroter, J. Ullrich, O. Herrwerth, M.F. Kling, X.-J. Liu, K. Motomura, H. Fukuzawa,
A. Yamada, K. Ueda, K. L. Ishikawa, K. Nagaya, H. Iwayama, A. Sugishima, Y. Mizoguchi,
S. Yase, Yao, N. Saito, A. Belkacem, M. Nagasono, A. Higashiya, M. Yabashi, T. Ishikawa,
H. Ohashi, H. Kimura, and T. Togashi, Optics Express 19, 21698 (2011).

Recoil ion detector

Split mirror
X

HeTime difference

FEL
1s2

Ion yield (counts/shot)

He+

He0

I2

Y
0.1

0.01

Split mirror assembly: MPI-K, ASG-CFEL, MPQ
Intensity (arb. units)
Mirror: Mg/Si multilayer (f=600 mm, LBNL)

Autocorrelation measurement with He two photon ionization

spike~7 fs
broad component ~ 30 fs

pulse duration=FWHM/ 2

Optics Express 19, 21698 (2011).

1.0
0.9
0.8
0.6
0.5
0.4
0.3
0.1
0.0
-0.1
-100

60
61
62
wavelength [nm]

63

-50

0
50
time [fs]

100

0.5
0.3
0.0
-0.3
-0.5
-0.8
-100

0.0
59

1.1
1.0
0.9
0.8
0.6
0.5
0.4
0.3
0.1
0.0
-0.1
-100

60
61
62
wavelength [nm]

63

-50

0
50
time [fs]

100

-50

0
50
time [fs]

100

0.5
0.3
0.0
-0.3
-0.5
-0.8
-100

-50

0
50
time [fs]

100

2.5
2.0
1.5
1.0
0.5
0.0
59
2.5

60
61
62
wavelength [nm]

63

2.0
1.5
1.0
0.5
0.0
-100

0.8
electric field [arb.u.]electric field [arb.u.]

0.8

0.5

electric field [arb.u.]59

spectral intensity density [arb.u.]

0.0

1.0

intensity [arb.u.]

0.5

spectral intensity density [arb.u.]

1.0

intensity [arb.u.]

intensity [arb.u.]spectral intensity density [arb.u.]

SCSS Sample Pulse Shapes

-50

0
50
time [fs]

100

-50

0
50
time [fs]

100

1.0
0.8
0.5
0.3
0.0
-0.3
-0.5
-0.8
-1.0
-100

Experimental evidence for competition between theresonant and non-resonant two-photon ionization
R. Ma, K. Motomura, K.L. Ishikawa, H. Fukuzawa, A. Yamada,
K. Ueda, K. Nagaya, S. Yase, Y. Mizoguchi, M. Yao, A. Rouzee,
A. Hundermark, M. Vrakking, P. Johnsson, M. Nagasono, K. Tono,
T. Togashi, Y. Senba, H. Ohashi, M. Yabashi, and T. Ishikawa

Photoelectron angular distribution for
two-photon single ionization of He
Direct numerical simulation of the two-electron
time-dependent Schrödinger equation (TDSE)

FEL
Velocity Map Imaging(VMI) spectroscopy

MCP +PhosphorscreenvsCCDcameraExcitation energies for two-photon ionization of He
Photon energy range available at SCSS test accelerator
Resonant
Coherent excitationof Rydberg manifold

Resonant
Nonresonant

W. F. Chan et al., Phys. Rev. A 44, 186 (1991).

Photoelectron angular distribution for two-photon ionization of He
20.3 eV21.3 eV23.0 eVResonant
Coherent excitationof Rydberg manifold

24.3 eVRed lines:
Measured PADs
Blue lines:
Results of the TDSE
calculations

Resonant

Nonresonant

R. Ma, K. Motomura, K. L. Ishikawa, H. Fukuzawa et al., submitted.

Photoelectron angular distribution for two-photon ionization of Hes
1  b 2 P2 (cos )  b 4 P4 (cos )
I ( ) 4

The outgoing photoelectron wave isa superposition of s and d waves.

Anisotropy parameters18
10  1 W b 
b2  2  cos d 
4
2
,
7
(
W
 1)
W 1 75W  c0 / c2 : Amplitude ratio ,see:
K. L. Ishikawa and K. Ueda,
Phys. Rev. Lett.,
108, 033003 (2012).

d  d 0  d 2 : Phase difference

cl : complex amplitude of a final state with an angular momentum l
δl : phase of each partial waveWδ
off-resonanceon-resonanceDeviation from scattering phase shift difference
The excitation laser is a shortpulse with finite width in both
energy and time!
Taking it into account, we have#δd  d SC  Arg c0 / c2 Additional
phase shift

Gien, J. Phys. B, 35, 4475 (2002).

δSC : scattering phase shift difference
K. L. Ishikawa and K. Ueda,
Phys. Rev. Lett., 108, 033003 (2012).

T: the pulse width

Deviationfrom δSC isevidenceof competition. Realand imaginaryparts
of cl correspondto thebetweenand non-resonant
pathsyresonant
andresonant
non-resonant
paths, respectivel
Tailoring continuum wavepacket controlling theadditional phase shift by the short EUV pulses !

Dependence of W and δ on the pulse width of
the Fourier transform limited pulse

T: the pulse width

Chirping the pulse width from 500 as to 20 fs, we can control
the contributions of direct and non-direct contributions
Tailoring the continuum wave packet (wave function)!
Ishikawa and Ueda, PRL 108, 033003 (2012).

Multiple ionization of rare gas atoms irradiated by EUV
free-electron laser pulses at 51 nm
K. Motomura, H. Fukuzawa, K. Papamihail, M. Kurka, A. Rudenko, L. Foucar,
H. Iwayama, K. Nagaya, X.-J. Liu, H.-U. Kühnel, G. Prümper, P. Labropoulos,
J. Ullrich, K. Ueda, N. Saito, H. Murakami, M. Yao, A. Belkacem, R. Feifel,
M. Nagasono, A. Higashiya, T. Togashi, H. Ohashi, and H. Kimura, M. Yabashi,
and T. Ishikawa
Ar 7+ > 434 eV> 18 photons

Kr 8+ > 508 eV> 21 photons
Mirror:Mg/Si multilayer
f=250 mm,made by LBNLSACLA XFEL
Photon energy range: 4-20 keV
Photon numbers: ～ 1011 photons/pulse (5-15 keV)
Repetition rate: 10~60 Hz
Pulse width ~10 fs
Focusing optics: ~1 µm (1.5 m) → 50 nm (0.5 m)
Commissioning beam time: Nov. 2011-Feb. 20127-11 Nov. 2011: Detector test (no real FEL beam…)
20-24 Feb. 2012: Serial femtosecond crystallography
User beam time started in March 2012
First two beam times in 2012:
Atoms, molecules and atomic clusters
Third beam time in 2013: pump-probe, failed
Project Leader: Tetsuya Ishikawa (RIKEN)
Fourth beam time in 2014:
Single-short imaging of giant xenon clusters
Fifth beam time in 2014:
Pump-probe experiment on clusters

Multi-photon, multiple ionization ofAtoms, Molecules and Rare-gas clusters
Single-shot imaging of Nano-clusters
Pump-probe experiments for

Atoms, Molecules and Rare-gas clusters
Aiming at probing
Ultrafast electron and structure dynamics

Experimental configuration @ SACLA BL3 EH3Reaction chamber
Al attenuator(t = 25 μm)

Gate
valve

Chargedparticle
spectrometer

PIN
photodiode

XFEL
Be window

KB mirror system
Focus point

XFEL pulses@Focus point
Photon energy: 5 and 5.5 keV
Focus size: 1-2 μm (FWHM)(Wavelength: 0.25 and 0.22 nm)
Peak fluence:
Band width: ~60 eV (FWHM)~47 μJ/μm2 (atoms, clusters),
Repetition: 10-30 Hz~26 μJ/μm2 (molecules)
Pulse energy before KB mirror:~240 μJ (~3×1011 photons) @5.5keV Sample gas were introduced asa pulsed super sonic gas jet toFluctuation of pulse energy:
the focus point.
±25% (50% FWHM)

I. Deep inner-shell multiphoton absorption
by intense x-ray free-electron laser pulses
H. Fukuzawa, S.-K. Son, K. Motomura, S. Mondal, K. Nagaya, S. Wada,
X.-J. Liu, R. Feifel, T. Tachibana, Y. Ito, M. Kimura, T. Sakai, K. Matsunami,
H. Hayashita, J. Kajikawa, P. Johnsson, M. Siano, E. Kukk, B. Rudek, B. Erk,
L. Foucar, E. Robert, C. Miron, K. Tono, T. Togashi, Y. Inubushi, T. Sato, T.
Katayama,T. Hatsui, T. Kameshima, M. Yabashi, M. Yao, R. Santra, andK. Ueda (PRL 110, 173005 (2013) & JPB 46, 164024 (2013).

Experimentalists

Theorists

Time of Flight spectrum of argon ions
KL23L23→2L23MM

XFEL
Ar jetXFEL fluence dependence for Arn+ yields
Ar4+: single photon K-shell ionization→ KL23L23 Auger → 2L23MM Auger
Ar3+: single photon K shell absorption→ KL23M Auger → L23MM Auger

Ar8+, Ar9+: sequential two photon Kshell ionization
Bench mark ab initio calculation
reproduces fluence dependence andrelative ratios.

In the theory, the pulse shape of Gaussianof 30 fs (FWHM), and Gaussian focal
shape of 1 μm (FWHM)×1 μm (FWHM)
are assumed.

Charge state distribution of Ar: experiment and theory

(30
(50
(70

By comparison with theory, we obtained peak fluence of
50 μJ/μm2 in the experiment!

Counts

5.5 keV, 50 μJ/μm2 at SACLA

X position(mm)Time of Flight spectrum of xenon ions
10
5
0

5000
4000
3000
2000
1000
0
6.6

6.7

6.8

132

Time129of131
flight (s)
134 136
128

6.6

130

6.7

6.8

Time of flight (s)

2D position resolved TOF
improves the resolution!

High charge states Xen+ with n up to 26 are produced!

XFEL fluence dependence for Xen+ yields

With help of ab initio calculations, we find that the observed high charge states (n ≥ 24)
are produced via five-photon absorption, evidencing the occurrence of multiphoton
absorption involving deep inner shells.

Xenon ion charge distributions (exper. vs theory)
5.5 keV, 50 μJ/μm2
at SACLA

A newly developed theoretical model shows good agreement withthe experiment!

An exemplary pathway of multiphoton multiple ionization

Xe24+

A newly developed theoretical model elucidates the complex pathways of sequential
electronic decay cascades accessible in heavy atoms, revealing that L shell ionizationand sequential electronic decay cycles are repeated multiple times within the XFEL
pulse duration of ~10 fs.
Fukuzawa, Son et al. PRL 110, 173005 (2013)

Relevance to other fields: Radiation damage
Radio-sensitizer

Anomalous X-ray scattering

5Br-Uracil

I

Multiwavelength anomalous diffraction at high X-ray intensity

5I-Uracil

S.-K. Son, H. N. Chapman, and R. Santra,
Phys. Rev. Lett. 107, 218102 (2011).

The endThank you very much foryour attention!