Manipulating and ProbingManipulating and ProbingManipulating and ProbingManipulating and ProbingAtomic and Molecular DynamicsAtomic and Molecular Dynamics

with Intense THz Pulseswith Intense THz Pulseswith Intense THz Pulseswith Intense THz Pulses

Bob JonesPhysics Department, University of Virginia, Charlottesville

Time Domain THz:Time Domain THz: FieldField--Induced or Driven Dynamics (active)Induced or Driven Dynamics (active)1.1. Observation and Control of ElectronObservation and Control of Electron--Electron InteractionsElectron Interactions

(Ex: within and between (Ex: within and between RydbergRydberg atoms)atoms)

22 Controlled RoControlled Ro--VibrationalVibrational Motion in MoleculesMotion in Molecules2.2. Controlled RoControlled Ro VibrationalVibrational Motion in MoleculesMotion in Molecules(Ex: Transient Field(Ex: Transient Field--Free Molecular Orientation)Free Molecular Orientation)

33 Manipulating HighManipulating High--Energy Electron TrajectoriesEnergy Electron Trajectories3.3. Manipulating HighManipulating High--Energy Electron TrajectoriesEnergy Electron Trajectories(Ex: to improve HHG, (Ex: to improve HHG, asecasec pulse generation, pulse generation, recollisionrecollision electron imaging)electron imaging)

Time Domain THz:Time Domain THz: FieldField--Induced or Driven Dynamics (active)Induced or Driven Dynamics (active)1.1. Observation and Control of ElectronObservation and Control of Electron--Electron InteractionsElectron Interactions

(Ex: within and between (Ex: within and between RydbergRydberg atoms)atoms)

22 Controlled RoControlled Ro--VibrationalVibrational Motion in MoleculesMotion in Molecules2.2. Controlled RoControlled Ro VibrationalVibrational Motion in MoleculesMotion in Molecules(Ex: Transient Field(Ex: Transient Field--Free Molecular Orientation)Free Molecular Orientation)

33 Manipulating HighManipulating High--Energy Electron TrajectoriesEnergy Electron Trajectories3.3. Manipulating HighManipulating High--Energy Electron TrajectoriesEnergy Electron Trajectories(Ex: to improve HHG, (Ex: to improve HHG, asecasec pulse generation, pulse generation, recollisionrecollision electron imaging)electron imaging)

F D i THF D i TH Hi h R l ti S t ( i )Hi h R l ti S t ( i )Frequency Domain THz:Frequency Domain THz: High Resolution Spectroscopy (passive)High Resolution Spectroscopy (passive)1.1. Explore Natural Spectrum of Isolated Atomic or Molecular SpeciesExplore Natural Spectrum of Isolated Atomic or Molecular Species

or Detect Species Abundanceor Detect Species Abundance(Ex: Molecular fingerprinting, molecular astrophysics,…)(Ex: Molecular fingerprinting, molecular astrophysics,…)

2.2. Monitor Influences of Local Environment or Detect Changes inMonitor Influences of Local Environment or Detect Changes inLocal EnvironmentLocal Environment

Creating SingleCreating Single--Electron Electron RydbergRydberg WavepacketsWavepacketsPicosecondPicosecond HalfHalf--Cycle PulsesCycle PulsesPicosecondPicosecond HalfHalf Cycle PulsesCycle Pulses

P

ψn

HCP

Coherent Transitions Between Coherent Transitions Between RydbergRydberg LevelsLevels |nlm>

e tiEn )( t),( nn

na rr

Ψn →y gy g

ψ0Intense HCP from Large Aperture Photo‐conductive switch:D. You, R.R. Jones,P.H. Bucksbaum, and D.R. Dykaar Opt. Lett. 18, 290 (1993).

Creating SingleCreating Single--Electron Electron RydbergRydberg WavepacketsWavepacketsPicosecondPicosecond HalfHalf--Cycle PulsesCycle PulsesPicosecondPicosecond HalfHalf Cycle PulsesCycle Pulses

P

ψn

HCP

Coherent Transitions Between Coherent Transitions Between RydbergRydberg LevelsLevels |nlm>

e tiEn )( t),( nn

na rr

Ψn →y gy g

Facilitated by:Facilitated by:Facilitated by:Facilitated by:i) Huge Transition Dipole Momentsii) Broad THz spectrum Extending to (near) DCiii) Multiple Pulses Varying Polarization

ψ0

iii) Multiple Pulses, Varying Polarization

See: RRJ, Bucksbaum, Noordam, Stroud, Robicheaux, Burgdorfer, Reinhold,…

pi

Probing SingleProbing Single--Electron Electron RydbergRydberg WavepacketsWavepackets with HCPswith HCPs“Impulsive Momentum Retrieval”“Impulsive Momentum Retrieval”pi

Kick

pp

Kickpi

IonizationIonization

Kick2A

21Ap

|Ψ(pi,t0)|2

RRJ, PRL 76, 3927 (1996); Robicheaux, PRA 56, R3358 (1997). Also See: Bucksbaum, Dunning, Burgdorfer, Reinhold,…

pi

Probing SingleProbing Single--Electron Electron RydbergRydberg WavepacketsWavepackets with HCPswith HCPspi

Kickz

E

Kickpi

IonizationIonization

Kick Radial+Angular Motion in Static Field2A

21Ap

|Ψ(pi,t0)|2

Campbell,Bensky,RRJ, PRA59, R4117(1999)

Control and Observation of 2Control and Observation of 2--Electron Dynamics Within an AtomElectron Dynamics Within an AtomStart from WellStart from Well--Defined Initial ConditionsDefined Initial ConditionsStart from WellStart from Well Defined Initial ConditionsDefined Initial Conditions

Classical View: Classical View: TimeTime--Dependent E, L for Individual ElectronsDependent E, L for Individual Electrons

-

∆∆tt ∆∆tt

2+

∆∆tt

2+-

∆∆tt2+

-

Quantum View: Quantum View: TimeTime--Dependent Correlation/EntanglementDependent Correlation/Entanglement

iEt )()()()E( iEt

jiet )r(ψ)r(ψ)(a)tE,,r,r( 2j1i

,ji,21

S. Pisharody and RRJ, Science 303, 813 (2004).

Double Double RydbergRydberg WavepacketsWavepacketsTimeTime--Dependent Energy ExchangeDependent Energy Exchange

n2 ,Z=2

gy ggy g

Wp

2D

BaBa wp 1 wp 2

HCP Delay

HCP

Nearly Immediate Decrease in Ba2+

Strong 2e interaction even at large separation?

X. Zhang, RRJ, F. Robicheaux, to be published.

Double Double RydbergRydberg WavepacketsWavepacketsTimeTime--Dependent Energy ExchangeDependent Energy Exchangegy ggy g

2e Wavepacket Survival Probability

Wp

2DDelay

Extremely Rapid Energy ExchangeExtremely Rapid Energy ExchangeConfirmed by Theory

X. Zhang, RRJ, F. Robicheaux, to be published.

Control and Observation of 2Control and Observation of 2--Electron DynamicsElectron DynamicsIn a Frozen DipoleIn a Frozen Dipole--Dipole Coupled Atomic GasDipole Coupled Atomic Gas '' ppIn a Frozen DipoleIn a Frozen Dipole Dipole Coupled Atomic GasDipole Coupled Atomic Gas

'

pp

'' ps

'' ss

E’E’'p

's'ps

'ssEE E’E’ εε ~ 2V~ 2V ’ ’’ ’

2'' ppss

rArB

REEs

'pp

'sp

EE--E’E’ εε 2V 2Vss ppss pp

2'' ppss

Single Atom Statesp ss

ps

Atom Pair Statespp

DipoleDipole--Dipole Interaction:Dipole Interaction:

3R)rR̂)(rR̂(3rr V BABA (~10MHz for n~30, R~5 μm)

Resonant Energy TransferResonant Energy Transfer: : EE11=E=E22

P l d L E it ti P l d L E it ti → 2)(' tit Pulsed Laser Excitation Pulsed Laser Excitation →  2)(' tietss

'2)( pp 0.8

1.0

System Evolves periodically fromSystem Evolves periodically fromto to with periodwith period ττ = 2π/= 2π/εε'ss 'pp0.4

0.6

Prob

abili

ty

0.0 0.5 1.0 1.5 2.0 2.5Time ()

0.0

0.2

E’E’'p

EE's

EEs

pρ ~ 109 cm-3 → ε ~ 1-100MHz

Single Atom States

Resonant Resonant WavepacketWavepacket TransferTransfer: : EE11=E=E22ii) P l d L E it ti f At A ) P l d L E it ti f At A →ii) Pulsed Laser Excitation of Atom A ) Pulsed Laser Excitation of Atom A →

ii) THz ii) THz WavepacketWavepacket Excitation Excitation →Oscillating Wavepacket on Atom A (THz frequency)

s

21tiEeps g p ( q y)

iii) Pulsed Laser Excitation of Atom Biii) Pulsed Laser Excitation of Atom B →

iv) Dipoleiv) Dipole--Dipole Coupled Evolution Dipole Coupled Evolution → 2'' )( 2 tEiepsp

2'1 seps tiE

iv) Dipoleiv) Dipole--Dipole Coupled Evolution Dipole Coupled Evolution →

WP Motion Transfer to Atom B and back (period 10 – 100 ns)

v) Probe WP motion/phase on Both atoms using 2v) Probe WP motion/phase on Both atoms using 2ndnd, Delayed THz Pulse, Delayed THz Pulse

2 epsp

v) Probe WP motion/phase on Both atoms using 2v) Probe WP motion/phase on Both atoms using 2 , Delayed THz Pulse, Delayed THz PulseWPs created by pump and probe interfere modulating amplitude in s, s’, p, p’

0.8

1.0

+0.4

0.6

P 3/2

Sign

al(a

rb.u

nits

)

WP A Oscillation

1.00 1.05 1.10 1.15 1.20Delay (ns)

0.0

0.2

P WP A Oscillation

Tao Zhou and RRJ (in progress)

A “better” THz Source ?A “better” THz Source ?11 Eliminate Strong Electric Transients Produced by Large Aperture Photoconductive Eliminate Strong Electric Transients Produced by Large Aperture Photoconductive 1.1. Eliminate Strong Electric Transients Produced by Large Aperture Photoconductive Eliminate Strong Electric Transients Produced by Large Aperture Photoconductive

SwitchSwitch

2.2. Suppress Low Frequency Radiation Components to Prevent HighSuppress Low Frequency Radiation Components to Prevent High--L ExcitationL Excitation2.2. Suppress Low Frequency Radiation omponents to Prevent HighSuppress Low Frequency Radiation omponents to Prevent High L ExcitationL Excitation

3.3. Enable generation of Identical Multiple Pulses and/or Pulse ShapingEnable generation of Identical Multiple Pulses and/or Pulse Shaping

4.4. Simple to ImplementSimple to Implement

Optical Rectification in Optical Rectification in MgOMgO doped Li:NbOdoped Li:NbO33TiltedTilted Pulse Front Velocity MatchingPulse Front Velocity MatchingRecent Review: János Hebling, Ka‐Lo Yeh, Matthias C. Hoffmann, Balázs Bartal, and Keith A. Nelson, JOSA B 25, B6 2008.

TiltedTilted--Pulse Front Velocity MatchingPulse Front Velocity Matching

Effi ie t Si gleEffi ie t Si gle C le THz Ge e tiC le THz Ge e ti

Original Proposal: János Hebling,Gábor Almási, Ida Z.Kozma, Jürgen Kuhl, Opt. Exp. 10, 1161 (2002).   

Efficient SingleEfficient Single--Cycle THz GenerationCycle THz Generation

Transient FieldTransient Field--Free Orientation of Polar MoleculesFree Orientation of Polar MoleculesImpulsive InteractionImpulsive InteractionImpulsive InteractionImpulsive Interaction

d

θF(t)F(t) cos d F(t) - d (t)F - U

Ult h t HCP d l A l KUltrashort HCP delivers an Angular Kick

∆t

∆t

∆t∆t

High Rotational Temperature:High Rotational Temperature:_Large Distribution of Initial Angular Momenta

Net ensemble orientation reduced at any given time_Net ensemble orientation reduced at any given time

LiH

Transient FieldTransient Field--Free Orientation of Polar MoleculesFree Orientation of Polar MoleculesHCP Creates MixedHCP Creates Mixed--Parity Rotational Parity Rotational WavepacketWavepacket LiH

|J0,M0> → Ψ(t) = Σ CJ |J,Μ0> exp(-iEJt)(need big fields due to small dipoles)

HCP Creates MixedHCP Creates Mixed--Parity Rotational Parity Rotational WavepacketWavepacket

J=6

J=5

HCP J=4

LargeLarge RotationalRotational TemperatureTemperature::

J=1J=2

J=3

Machholm and Henriksen, PRL 87 193001 (2001).

gg pp_Unpure initial state.PJ,M ~(2J+1) Σexp [-J(J+1)B0/kBT ]

Redu ed Wa epa ket Cohe en eJ=0J=1 _Reduced Wavepacket Coherence

_Reduced Orientation

Transient FieldTransient Field--Free Orientation of Polar MoleculesFree Orientation of Polar MoleculesWorks with FullWorks with Full--Cycle Pulses Too! Cycle Pulses Too! (CE(CE--Phase Determines orientation direction)Phase Determines orientation direction)Works with FullWorks with Full Cycle Pulses Too! Cycle Pulses Too! (CE(CE Phase Determines orientation direction)Phase Determines orientation direction)(less efficient because of poor spectral overlap at low J transitions)(less efficient because of poor spectral overlap at low J transitions)

Work Work AroundsArounds::i)i) Very High Fields Very High Fields

All transitions involving dipole moments ~1 All transitions involving dipole moments ~1 a.ua.u. or larger and frequencies <1 THz . or larger and frequencies <1 THz saturate in a 1 THz field with an amplitude > 1 MV/cmsaturate in a 1 THz field with an amplitude > 1 MV/cm

ii)ii) Optical PreOptical Pre--AlignmentAlignmentRaman Redistribution in Optical Field coherently transfers population to high J Raman Redistribution in Optical Field coherently transfers population to high J states which have better overlap with singlestates which have better overlap with single--cycle bandwidthcycle bandwidthstates which have better overlap with singlestates which have better overlap with single--cycle bandwidthcycle bandwidth

0 2

0.4

0 2

0.4500 kV/cm 1 ps HCP 500 kV/cm 2 ps FCP150 kV/cm 2 ps FCP w/ and w/o 1013 W/cm2 100 fs laser pulse

-0.2

0.0

0.2

<cos>

-0.2

0.0

0.2

<cos>

OCSAt 1K

-50 0 50 100 150Delay (ps)

-0.4

-50 0 50 100 150Delay (ps)

-0.4

Transient FieldTransient Field--Free Orientation of Polar MoleculesFree Orientation of Polar MoleculesRecent Demonstration with Weak FCP and Room Temperature OCSRecent Demonstration with Weak FCP and Room Temperature OCSRecent Demonstration with Weak FCP and Room Temperature OCSRecent Demonstration with Weak FCP and Room Temperature OCSSharly Fleischer, Yan Zhou, Robert W. Field, and Keith A. Nelson, PRL 107, 163603 (2011).

Probes:Probes:Optical birefringence and Coherent THz EmissionOptical birefringence and Coherent THz Emission(infer <cosθ> ~ 1%)

Also see: C.M. Herne “Shaping Terahertz Fields for the Orientation of Asymmetric Top Water Molecules,” Ph.D. Dissertation, Univ. of Michigan, 2008.

Optical Rectification in Optical Rectification in MgOMgO doped Li:NbOdoped Li:NbO33TiltedTilted Pulse Front Velocity MatchingPulse Front Velocity MatchingTiltedTilted--Pulse Front Velocity MatchingPulse Front Velocity Matching

Improved Optics:Improved Optics:_Higher Output Energy_Higher Output Energy_Better Focusing_Better Focusing

H. Hirori, A. Doi, F. Blanchard, and K.Tanaka, APL 98, 091106 (2011).

Noble Gas Atom in Intense Laser FieldNoble Gas Atom in Intense Laser Field ((ω << ω << IP)IP)Single Active Electron (SAE) Tunneling Single Active Electron (SAE) Tunneling Single A tive Ele tron (SAE) Tunneling Single A tive Ele tron (SAE) Tunneling Ionization Rate: Γ(I, IP)

IPy

e-IPEnergy

Field Axis (z)Field Axis (z)

Keldysh, Sov. Phys. JETP 20, 1307 (1965); Ammosov, Delone, Krainov, Sov. Phys. JETP 64, 1191 (1986).

Noble Gas Atom in Intense Laser FieldNoble Gas Atom in Intense Laser Field ((ω << ω << IP)IP)

e‐

UUe‐

High Energy Electrons (ATI)High Energy Electrons (ATI) E<10 UE<10 UppRecently Exploited for Diffractive ImagingRecently Exploited for Diffractive Imaging

< 3.2 U< 3.2 Upp

Argon

UUpp = F= F22/4/4ωω22 (a.u.)(a.u.)“pondermotive energy”“pondermotive energy”pondermotive energypondermotive energy

Nandor, Walker, Van Woerkom and Muller, PRA 60, R1771 (1999)

ATI – Agostini, Freeman, Bucksbaum, Muller, ….. ‘Rescattering’ - Corkum, Kulander, Schafer,..Laser Induced Electron Diffraction (LIED): Bandrauk, Corkum, DiMauro, C.D. Lin, ….

Noble Gas Atom in Intense Laser FieldNoble Gas Atom in Intense Laser Field ((ω << ω << IP)IP)

Hi h E Ph t E IP 3 2 UHi h E Ph t E IP 3 2 U e-

UU

High Energy Photons E < IP+3.2 UHigh Energy Photons E < IP+3.2 Upp(HHG and (HHG and AttosecondAttosecond Pulses)Pulses)

< 3.2 U< 3.2 Upp

UUpp = F= F22/4/4ωω22

“pondermotive energy”“pondermotive energy”pondermotive energypondermotive energyMacklin, Kmetec, and Gordon, PRL 70, 7166 (1993)

HHG – Rhodes, l’Huillier, Murnane, Kapteyn, Krausz…

Wanted….Wanted….Higher Harmonics and Higher Energy Higher Harmonics and Higher Energy RecollisionRecollision ElectronsElectronsHigher Harmonics and Higher Energy Higher Harmonics and Higher Energy RecollisionRecollision ElectronsElectrons(Without Additional Ionization)(Without Additional Ionization)

Eff ti A h Eff ti A h Effective Approach: Effective Approach: Longer Wavelengths → Higher Up for Same Peak Field and Tunneling Rate(some other advantages for attosecond pulse generation too)*g p g

Can This be Extended to the THz Regime?Can This be Extended to the THz Regime?

*See DiMauro

High Energy Electrons from SingleHigh Energy Electrons from Single--Cycle THz IonizationCycle THz Ionizationof Excited Sodium Atomsof Excited Sodium Atomsof Excited Sodium Atomsof Excited Sodium Atoms

(No Ground State Ionization at Fields Below ~50 MV/cm) (No Ground State Ionization at Fields Below ~50 MV/cm)

10-1

100

s)

n=7n=8n =9n=10

360 kV/cm, 2 ps Single-Cycle Sine Pulse

10-2

0

d(a

rb.u

nits n=10

n=11n =12n = 13

10-3Yie

ld

0 10 20 30 40 50 60 70Electron Energy (eV)

10-4

S.Li and RRJ, to be published

THz Field CalibrationTHz Field CalibrationTHz Streaking of THz Streaking of FemtosecondFemtosecond PhotoelectronsPhotoelectronsgg

400

Momentum Transfer vs.Photo-Ionization Time

F(t) from Derivative ofMomentum Transfer

Comparison of Measured and Calculated

V/c

m)

3

fer(

a.u.

)

200

m)

10% Ionization Thresholds

105

Fiel

d(V

1

2

omen

tum

Tran

sf

-200

0Fi

eld

(kV

/cm

101

n

104

-10 -5 0 5 10Delay (ps)

0

Mo

-10 -5 0 5 10Delay (ps)

-400

200

y (p )

Predicted “THz” Modifications to Predicted “THz” Modifications to RecollisionRecollision Electrons in Optical FieldElectrons in Optical Field(Assumed Quasi(Assumed Quasi--Static Field) Static Field) F=0.1FL~100 MV/cm

A. Lohr, W. Becker, and M. Kleber,Laser Physics 7, 615 (1997). =F/FL

Harmonic Plateau and Harmonic Plateau and RecollisionRecollisionEnergy Extension To 10 UEnergy Extension To 10 Upp

Bingbing Wang, Xiaofeng Li and Panming Fu,JPB 31, 1961 (1998).

Increase in Increase in RecollisionRecollision Energy withEnergy withd S fd S f

L

Return Time and Suppression ofReturn Time and Suppression ofMultiple ReturnsMultiple Returns

RescatteringRescattering from from RydbergRydberg Stark EigenStark Eigen--States in SingleStates in Single--Cycle THzCycle THzi)i) StrongStrong--Field Ionization Not RequiredField Ionization Not Requiredgg qqii)ii) RecollisionRecollision wavepacketwavepacket Extremely well characterizedExtremely well characterizediii)iii) RydbergRydberg states exist in all moleculesstates exist in all moleculesiv)iv) RecollisionRecollision confined to one direction relative to moleculeconfined to one direction relative to moleculeiv)iv) RecollisionRecollision confined to one direction relative to moleculeconfined to one direction relative to molecule

0 5

1.0

ts)N=30 yields ~100 eV electrons on ion

-0.5

0.0

0.5

Elec

tric

Fiel

d(a

rb.u

nit

For ~15 THz Single-Cycle Sine Field of ~15 MV/cm

-1 0 1 2 3Time (ps)

-1.0

E

New Sources May Get Us Into this Interesting RegimeNew Sources May Get Us Into this Interesting RegimeFF 1010 100 MV/cm100 MV/cmFFTHzTHz =10=10--100 MV/cm100 MV/cm

Difference Frequency Mixing of 2 OPAsCoherent Transition Radiation from LCLS electrons

F. Junginger, A. Sell, O. Schubert, B. Mayer, D. Brida, M Marangoni G Cerullo A Leitenstorfer and R

Dan Daranciang, John Goodfellow, Matthias Fuchs, Haidan Wen, Shambhu Ghimire,

M. Marangoni, G. Cerullo, A. Leitenstorfer, and R. Huber, Opt. Lett. 35, 2645 (2010).

David A. Reis, Henrik Loos, Alan S. Fisher, and Aaron M. Lindenberg, APL99, 141117 (2011).

Summary:Summary:Summary:Summary:

A wide range of Atomic and Molecular Physics problems can be A wide range of Atomic and Molecular Physics problems can be Explored/Enabled by THz Radiation (far more than presented here). Explored/Enabled by THz Radiation (far more than presented here).

Intense new sources are making it possible to impact physics in energy Intense new sources are making it possible to impact physics in energy nt ns n w sour s r m ing it possib to imp t physi s in n rgynt ns n w sour s r m ing it possib to imp t physi s in n rgyand time regimes beyond those typically associated with the THz and time regimes beyond those typically associated with the THz spectrum. spectrum.