QuEBS – I. P. Mercer 9th July 2009

1

Ian Mercer

ian.mercer@ucd.ie

Thu 9th July 2009

Quantum dimension

of photosynthesis

revealed by

Angular Resolved

Coherent (ARC) imaging

Collaborators

Yasin C. El-Taha1, Nathaniel Kajumba1, Jonathan P. Marangos1, John W. G.

Tisch1, Mads Gabrielsen2, Richard J. Cogdell2, Emma Springate3, Edmund Turcu3

1) Quantum Optics and Laser Science Group, Blackett Laboratory, Imperial College, UK.

2) Biochemistry and Molecular Biology, Faculty of Biomedical and Life

Sciences, University of Glasgow, UK.3) Central Laser Facility, STFC Rutherford Appleton Laboratory, Didcot, UK.

•BBSRC, EPSRC funding, •EU Framework 6 Lab Share programme

Acknowledgements: Steve Hawkes3, Oleg Chekhlov3, Klaus Ertel3, PetaFoster3, Rob Heathcote3, David Neely3, John Collier3, Steve Blake3, Pete

Brummit3, Paul Donaldson, Andrew Gregory1, Peter Ruthven1

Transfers of energy:

photosynthetic apparatus in membranes

2H2O O2 + 4H+ + 4e-

–

+

2.5nm

CO2 + H2O T (CH2O) + O2

light

Antenna

Quarterly

Rev Biophys

39, 3, 227–

324 (2006)

Ambient

temperatures

Optical methods

Tunable

Excitation

Pulse

White Light Probe

Pulse

Sample

Optical Detector

Tunable

Excitation

Pulse

Sample

Electronically Gated

Optical Detector

Fluorescence

Three Excitation

Pulses

Sample

Optical Detector

Photon

Echo

Transient Absorption(to

determine paths and rates)

Three Pulse Photon Echo (to

determine electron-vibration

couplingPicosecond Emission

(to determine free

energy gaps)

The echo (spin and photon) is the

time-domain equivalent of the hologram

Iecho ∝ I1 I2 I3t3ST12 T23

Analogy with a hologram: data storage

FILM

Collimatd

light

FILM

Collimatd

light

Chl-a and Bchl-a: 3 pulse echo peak shift

ττττ T

3PEPS laser echo experiment QM/MM simulation•MOPAC

PM3

•Gaussian

STO-3G

CIS 10-10

Nonlinear Optical

Response TheoryCho, Walker, Amer, Mercer, Klug, Gould,

J.Phys.Chem. B 109 5954 (2005)

Mercer, Gould, Klug, J.Phys.Chem.B, 103,

36, 7720 (1999)

Mercer, Abend, Gould, Klug, Spinger Series

in Chem Phys 63, 532 (1998)

Mercer, Gould, Klug, Faraday Discussions

108, 51 (1997).

0 200 400 600 800 10000

5

10

15

Energy

Time /femtoseconds (fs)

Imperial, UK

QuEBS – I. P. Mercer 9th July 2009

2

Electronic energy level

flucutations due to

thermal bath

(vibrations)

TimeEnergy

Probability

Histogram of

energy against

probabilityProbability ratio is related to

eqm. Constant

2

1

E

E

P

PK =

Energy

Gives free

energy

surfaceDG

DG = - RT ln K

Energy fluctuations give shape of free

energy surfacesThe shape of free energy surfaces

-0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5

0

1

2

3

4

5

6

Semi-empirical

Ab.initio.

Electronic Transition Energy /eV

Relative free energy / k BT

Are they Parabolic? Does it matter?

No Yes

∆∆∆∆G

Ea

Complex exciton

dynamics in B850

LH2 B800/B850 antenna

Can we better distinguish

coherent from incoherent

coupled electronic transitions?

B800

B850

k’

k

Transfers of energy: the role of waves?

3PEPS in LH2 B850

Coherent coupling between

electronic transitions

+

Electronic-phonon energy transfer

+

Electronic-electronic energy transfer

Similar seen in LH1

Distinguish energy transfer mechanisms?

Decay time 160fs

3PEPS in LH2 B850

Coherent coupling between

electronic transitions

+

Electronic-phonon energy transfer

+

Electronic-electronic energy transfer

Similar seen in LH1

Vertical feature

translations

Vertical feature

translations

Vertical discrete

shifted features

Vertical discrete

shifted features

ARC

imaging:

Horizontal shifts

ARC

imaging:

Horizontal shifts

Distinguish energy transfer mechanisms?

Decay time 160fs

QuEBS – I. P. Mercer 9th July 2009

3

Angular Resolved Coherent

(ARC) imaging

Signal deviation only 0.01o

for 5nm between interactions

T12 T23

∆

δ

sω

δ

1k−

2k 3k S

k

2ω1ω−

3ω

b’

a’

a

b

321 kkkkS ++−=

PhysRev Lett 102, 57402 (2009)

Angular Resolved Coherent (ARC) imaging

gSdiff dλθ =

Patent pending

Ideal laser source

• High intensity: 20fs, 1kHz, 1 - 100mJ • Hollow fibre – stable, robust, high spatial quality,

up to 500nm coherent bandwidth

Robinson et.al., Appl. Phys. B 85 (525–529) (2006); Nisoli et.al. (1996)

750 800 850 900

Wavelength /nm

Intensity (arb.units)

0.05

0.10

B850

B800

Sample O

DEnergy transfer:vertical shift only

Coherently coupled transitions:

horizontal shift only

( )

S

vv

vvSv

ωα

αωαω

∆=Φ

+Φ=2 (ii)

Sωωωω == 321

Sωωωω == 231

( )

S

hh

hhS

ω

δα

αωωω

=Φ

−=Φ 21 (iii)

Horizontal plane Vertical plane

(i) (ii)

(iii) (iv)

Small angles approximation

0 (iv) =Φv

0 (i) =Φh

3kkS = 21 kk =h

α

h

h

v

v

vα

vΦSk

3k

2k

1k

21 kk +−

vαhα

hΦ

hα

Sk

1k

2k

3k 2kkS =

31 kk =

321 kkkkS ++−=

Linear array

spectrometer

Heterodyned approach: comparison

Each detector array pixel collects over all excitation energies:

computer post processing to disentangle

Engel et al.

Computer processing

ARC-TG of LH2 B800/B850

Can use a single pulse at 0.1

excitations/ring to get a full map

λ

Transfer time 0.8ps as for standard TG

QuEBS – I. P. Mercer 9th July 2009

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T23=1.3ps

ARC-TG map LH2 (acidophila)

B800/B850, T = 1.3 ps

Conservation of momentum:

Φv = ±2.0mrad,

∆ = ±770cm-1

as expected

852nm 800nm

signal filtering

(long time delay)

321 kkkkS ++−=

Overlaid signal filtered maps

231 ,, kkk

(i)

(ii)

(ii)

(i)

(ii)

321 ,, kkk0 ps

2.8 ps

Imposed time ordering

321 ,, kkk

Two time orderings

symmetric about diagonal

321 ,, kkk

231 ,, kkk

(i)

Sensitivity to site energy correlation

Alignment at T23 > 1ps predicted for

system homogenisation

∆

sω

1k− 2k 3k Sk

aωdiagonal

1=Sa dd ωωβ

ωS decrease

∆ increase

ωa = constant

ωa = ωS + ∆

ωa = ωS

-ve correlation

+ve correlation

Emission filtered at 880nm

λ

∆= +260 cm-1

δ = +120 cm-1∆= +400 cm-1

δ = 0 cm-1

Signal bandwidth filter

(880±5)nm: B850 Excitation prob.

0.1/ring

R42604

Directly distinguish coherent electronic motion:

beat frequency (δ), reduces with τ = 160fsDemonstrated for the first time

• Orthogonal dimensions for coherent and incoherent

couplings between an arbitrary number of transitions

• No post-processing

• Laser beam interaction energies for each quantum

pathway for arbitrary number of transitions

• Instantaneous: single laser pulse in principle

• High dynamic range

QuEBS – I. P. Mercer 9th July 2009

5

Exploring problems

• Protein function/structure

• Solar cells

• FRET

• Coherent control

•Non-reversible chemical reaction

• Photo-sensitive, high value samples

• Rapid sampling

Method

•Wave-mixing schemes

• Spanning the optical spectrum:

few optical cycles and high pulse energy

x-ray visible near-IR

Laser source capability….

T12T23

1k− 2k 3k Sk

2ω1ω−

3ω

ω3 = 45,000cm-1, ωS = 60,600cm

-1

Coherent couplings:

signatures of protein structure?

220nm

170nmMaps distinguishing

coherent coupling

components

(fingerprints)?

T23=1.3ps

Selecting before detection

• Saturate/block strong features to detect weak features

•Direct, linear subtraction of background light

Separation

according to

excitation energy

prior to detector

Interference of coherent pathways??

~ps

~100fs

B800

B850

~ps

Broadly similar coupling strength

within B800 as for B800 to B850

Gives one potential interfering pathway ?

3PEPS B800

Agarwal et.al., J Phys Chem B 105 p1887 2001

QuEBS – I. P. Mercer 9th July 2009

6

ARC-3PE

Vary T12 T23 = 1 ps

T12 T23

00

0b ′

ab

ab ′′

a0

00

T12 T23

1k− 2k 3k Sk

2ω

1ω−

3ω

b’a’

ab

CCD images as detected. Preliminary data (in analysis).

T12 = 0 - 450fs

Arb. scaling