NSF Panel on Light Source Facilities
AMO Physics Applications:
a fruitful partnership
Philip Bucksbaum
Stanford
Wednesday, January 10, 2008
Resources on AMO Research in 2010
and Beyond
• AMO 2010: Controlling the
Quantum World
• National Academy decadal survey
• Controlling Matter and Energy:
Five Challenges for Science and
the Imagination
Controlling Matter and
Energy: Five
Challenges for Science
and the Imagination
• Report from the Basic Energy
Sciences Advisory Committee
(BESAC)
January 10, 2008
NSF Panel on Light Source Facilities
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Frontier areas of AMO
• High precision clocks – the precision time
frontier.
• Imaging quantum processes on ultrafast time
scales – the attoscience frontier
• Coherent molecular dynamics – the quantum
control frontier
• Quantum computing and quantum
communication: the quantum information
frontier
• Atomic physics in exotic environments: the high
field and high energy density frontiers
• Ultralow temperature phenomena: the frontier of
quantum degenerate atomic gases
January 10, 2008
NSF Panel on Light Source Facilities
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Areas that make use of light source
facilities
• High precision clocks – the precision time
frontier.
• Imaging quantum processes on ultrafast time
scales – the attoscience frontier
• Coherent molecular dynamics – the quantum
control frontier
• Quantum computing and quantum
communication: the quantum information
frontier
• Atomic physics in exotic environments: the high
field and high energy density frontiers
• Ultralow temperature phenomena: the frontier of
quantum degenerate atomic gases
January 10, 2008
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The facilities of interest
for AMO frontier physics
Megajoule lasers
X-ray lasers
LCLS
Synchrotrons
ALS
NIF Target Chamber
Smaller centers also
contribute petawatt lasers
for collaborative use
(Texas Petawatt, FOCUS)
January 10, 2008
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Atomic Clocks
From military navigation to fundamental physics, atomic clocks are central.
Atomic clock in a
1 mm3 volume
January 10, 2008
U.S. primary frequency standard: Cs
atomic fountain clock, accurate to
5 X 10-16 or
1 second in 60 million years
NSF Panel on Light Source Facilities
Optical frequency
standards (Nobel ’05) are
the future of atomic clocks
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Connection I: Precision VUV Metrology
Applications:
Precision vuv atomic
spectroscopy
Optical time standard
Time variations of fundamental
processes
Jones et al. PRL 94, 193201 (2005)
January 10, 2008
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Connection II: Attosecond precision to tame
the SASE FEL
Energy modulation in the
wiggler at ~ 4 GeV
Acceleration
Peak current, I/I0
Modulation
Only one optical cycle is shown
•Laser peak power ~ 10 GW
•Wiggler with ~ 10 periods
Bunching
20-25 kA
50 fs laser pulse
λL= 2 microns
z /λL
•Electron beam after bunching
at optical wavelength
P. Emma, W. Fawley, Z. Huang, S. Reiche, G. Stupakov, A. Zholents
January 10, 2008
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The output x-ray radiation from a single micro-bunch
~200 as
-200
-100
0
100
200
• Each spike is nearly temporally coherent and Fourier transform limited
• Carrier phase for an x-ray wave is random from spike to spike, but HGHG
injection schemes could overcome this
• Pulses less than 100 attoseconds may be possible with 800 nm laser
January 10, 2008
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High Field Frontier: Changing Strong Field
Regimes Inside Atoms
IR:
Low frequency regime
- Ip
VUV FEL:
Intense photon source
- Ip
Γe − A+ < ωlaser
Γe − A+ > ωlaser
U P << hωlaser
Γnγ →e − A+ ≈ Γn +1γ →e − A+
ATI, HHG
January 10, 2008
- Ip
10x20 W/cm2
1013 W/cm2
1015 W/cm2
U P > hωlaser
X-RAY FEL:
Highly ionizing source
Γe − A+ ≈ Γ2e − A+ + ?
sequential vs.
non - sequential
NSF Panel on Light Source Facilities
Γe − A+ << ωlaser
U P << hωlaser
Γe − A+ ≈ ΓAuger ,Γ2e − A+ +
Hollow atoms?
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Laser Power Beyond a Petawatt can
access Relativistic Strong Field Physics
Relativistic
photoionization
and rescattering
of photoelectrons
and ions
January 10, 2008
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Can the LCLS get to its own type of
strong-field regime?
• impose a Keldysh parameter of one
γ ≡ 1 = (Ip/2Up)1/2 ⇒ Up ≅ 400 eV (8 eV)
@ 800 eV, intensity needed is 1021 W/cm2 (1014 W/cm2)
number of photons is fixed, require tighter focus and shorter pulse
τlcls ~ 10 fs (very possible)
thus require a beam waist of 50 nm (in principle possible)
lcls II
10
10
10
10
1
10
-1
10
MPI
-3
tunnel
-5
MPI
tunnel
µλ
10
µλ
-7
10
10
-9
10
-6
10
-3
10
0
field amplitude (au)
January 10, 2008
10
3
10 0.1
1
10
1
-1
-3
-5
-7
frequency (au)
frequency (au)
10
100
keldysh parameter, γ
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Strong field wavelength scaling:
Keldysh picture
optical frequency
tunneling frequency
γ≡
= (Ip/2Up)1/2 ∝ λ-1
lcls
γ>1
10
10
10
10
10
γ<1
-1
10
excimer
MPI
Ti:sap & Nd
mir
-3
CO2
tunnel
“photon description”
-5
tunnel
µλ
10
MPI
µλ
10
-9
10
-7
10
-5
10
-3
10
-1
field amplitude (au)
1
10 0.1
-1
-3
“dc-tunneling picture”-5
10
-7
10
1
1
10
-7
frequency (au)
frequency (au)
10
1
100
keldysh parameter, γ
• data compiled based on both electron and ion experiments
January 10, 2008
NSF Panel on Light Source Facilities
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Physics comes from inner shells
• laser multiphoton ionization
neon photoabsorption
n=2
n=1
• x-ray multiphoton ionization
January 10, 2008
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x-ray strong field experiment
x-ray multiphoton ionization
photoionization
correlated ionization
Auger
sequential
2-photon, 2-electron
January 10, 2008
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1-photon, 1-electron ionization
consider a 1-photon K-shell transition:
σK ≈ 10-18 cm2
ΓK = σKFlcls ≈ 1015 s-1
(saturated)
tK = 1/ Γ K = 1 fs
photoionization
• rapid enough to ionize more than one electron!
• fast enough to compete with atomic relaxation?
neon photoabsorption
L-shell
K-shell
January 10, 2008
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2-photon, 2-electron ionization
2-photon, 2-electron
• are the electrons correlated?
• in a strong optical field single electron dynamics dominate.
i.e. is it sequential ionization?
photoionization
January 10, 2008
Auger
photoionization
NSF Panel on Light Source Facilities
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Coherent effects?
• 3d generation x-ray sources have << 1 photon
per mode; LCLS will have coherence “spikes”
containing a billion photons or more, in
~femtoseconds! What about coherent
excitation?
Rabi rate Ω ≈ µF0
−1
µ = f ex i ≈ Ebinding
≈ 0.01 for 1keV
F0 ≈ 1 then implies Ω −1 ≈ 2.5 fsec
January 10, 2008
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Attosecond pump-probe?
fundamental time scale electron dynamics Atomic time unit = 24 attoseconds
Direct attosecond probe of atomic electron correlation Hu and Collins, PRL (2006)
Theory
January 10, 2008
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Observing the inner workings of an atom:
Auger dynamics
• Dynamics driven by
electron correlation
effects
• Time-scale important
in atoms, molecules,
nano-particles (i.e.
multiple-exciton
generation)
• Attosecond pumpprobe expts proposed
for NGLS (Berkeley
workshop, 2007)
January 10, 2008
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The competition for attoscience: HHG, a
source of controllable vuv radiation
Phosphor
Screen
CCD
Camera
MCP
Mirror
f=400
Nozzle
Grating
Al Filter
on Gate
Valve
Jet
Mirror
Mirror
Turbo
Pump
Prevac
Turbo
Pump
Prevac
January 10, 2008
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HHG mecanism involves rescattering,
and so is limited to the atomic scale
a)
time
Energy [a.u.]
Energy, Amplitude [a.u.]
c)
time
b)
hν
classical
E Field
E Field
E Field
Uion
-
e
d)
e)
f)
|ψ|2
quantum
-4
-2
0
r [a.u.]
January 10, 2008
Recombination
Acceleration
time
Ionization
2
4
-4
-2
0
2
4
-4
-2
r [a.u.]
NSF Panel on Light Source Facilities
0
2
4
r [a.u.]
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Imaging the Inner Workings of a Molecule
A snapshot image of a molecule
obtained from field ionization and electron-molecule recollision
Can we get this degree of control with radiation from a facilitiy?
January 10, 2008
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Diffraction imaging with x-rays at LCLS
Particle injection
Pixel
detector 1
Intelligent
beam-stop
XFEL beam
(focused, possibly
Compressed)
To mass
spectrometer
January 10, 2008
Optical and xray
diagnostics
NSF Panel on Light Source Facilities
Readout and
reconstruction
24
Exploding T4 Lysozyme:
Short pulses and high power are essential
1x1011W/cm2 irradiation for 200 fs by LCLS pulse in 1mm spot (unfocused)
January 10, 2008
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A 3D dataset can be assembled from diffraction patterns in
unknown orientations
Diffraction from a single molecule:
Noisy
diffraction
pattern
FEL pulse
Unknown
orientation
Combine 105 to 107 measurements into 3D dataset:
Classify
Average
Combine
The highest achievable resolution is limited by the ability to
group patterns of similar orientation
Gösta Huldt, Abraham Szöke, Janos Hajdu (J.Struct
Biol, 2003 02-ERD-047)
January 10, 2008
NSF Panel on Light Source Facilities
Reconstruct
Miao, Hodgson, Sayre, PNAS
98 (2001)
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Beyond imaging: Controlling quantum
evolution
tools for control
Total field control
-Ultrafast studies (1999 Nobel)
-Carrier envelope phase control (2005 Nobel)
-Pulse shapers
January 10, 2008
Learning feedback
NSF Panel on Light Source Facilities
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Ultrafast vuv control will involve extreme nonBorn-Oppenheimer dynamics
Launch dynamics on multiple potential energy
surfaces
hν
Create electronic wavepacket: superposition on several
electronic surfaces
January 10, 2008
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Partnership: Light sources will
contribute richly to AMO Science…
Megajoule lasers
X-ray lasers
LCLS
Synchrotrons
January 10, 2008
ALS
NIF Target Chamber
…and AMO will
contribute techniques
and technology to
utilize these sources
for science.
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Thanks to…
•
•
•
•
•
•
•
January 10, 2008
Lou DiMauro
Linda Young
Markus Guehr
Bill McCurdy
Joe Stohr
Janos Hajdu
Many others…
NSF Panel on Light Source Facilities
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