1. Intense laser field interaction with molecular ions Daniel Strasser
Institute of Chemistry
Hebrew University of Jerusalem
Batsgeva De Rothschild Seminar 2012
Ultrafast laser – molecular ion lab
2013
Ultrafast EUV Probe
Project
time
Oct 2009
2011

2. for Molecular Reaction Dynamics
Ultrafast EUV Probe
for Molecular Reaction Dynamics
Time resolved single photon Coulomb explosion imaging

3. e- - molecule reactions exhibit extremely non-B.O. dynamics
example: ECD of Biomolecules
( Electron Capture Dissociation )
R-N+H3 + e-
(R-NH3)•*
superexcited
state
R-NH2 + (H•)hot
R• + NH3
R.A. Zubarev et al. EJMS (2002)

4. e- - molecule reactions are everywhere
Molecular cloud
Barnard 68
European Southern Observatory:
Alves, J. F., Lada, C. J., and Lada, E. A.
example: Dissociative Recombination of molecular ions e-
H3+
superexcited
H3 state 10 5
H3+ DR (fragment imaging)
D. Strasser et al. PRL (2001)

5. Time resolved probing of e- – molecule reactions
New basic insights beyond B.O.
into chemical reactions

6. Can we time resolve e- – molecule dynamics ?
Need Ultrafast EUV Photons
AB+ + e-
AB**
(SES)
AB + hn
A + B*

7. Ultrafast EUV shources:
Accelerator based FEL facilities:
( LCLS, FLASH, …)
table top HHG sources:
“simply” focusing intense IR into rare gas
~5x1014 W/cm2 in 10 PSI Ar
≥ 106 photons/15th/pulse

8. Ultrafast SES dynamics
N2+ + e-
N + N*
N2 + hn
Pump: 53.7 nm
Probe: 800 nm
Ultrafast Predissociation time ≤ 25 fs
short lived
N* (3d or 4p)
D. Strasser et al. Mol. Phys. (2008)
at Berkeley with Steve Leone

9. Anionic Superexcited States
AB + e-
NIR-VIS photons
AB**-
(SES)
AB- + hn
A- + B*
other advantages:
mass selectivity
fast beam fragment imaging

10. My Dream

11. and now with Coherent Control …

12. Laser system: Mai-Tai Oscillator Spitfire Amplifier
< 25 fs
< 4 mJ/pulse
@ 1kHz
OPA-800
oscillator
amplifier
Pulse Shaper
128 spectral pixels of phase & amp. control

13. Fast beam fragment imaging
shaped ultrafast, or
pump-probe pulses
imaging
detector
measure
molecule
{ vi }
vbeam
{xi, yi, ti }
~1,000,000 m/s L
t ~ ns
x ~ cm
Coincidence detection of
all possible products:
Cations, Anions, Neutrals and electrons

14. Fast beam fragment imaging
shaped ultrafast, or
pump-probe pulses
imaging
detector
measure
molecule
{ vi }
vbeam
{xi, yi, ti }
~1,000,000 m/s L
mass gate
electrodes
pulsed ion beam

15. Fast beam fragment imaging
ultrafast
pump-probe pulses
imaging
detector
measure
molecule
{ vi }
vbeam
{xi, yi, ti }
~1,000,000 m/s L
Experiments that are now possible:
-Photodetachment, Photodissociation
-Intense laser field – anion interaction
-Pulse shaping, Coherent control and more
-Coulomb explosion
-Pump-Probe : Time resolve SES dynamics

16. test: H2O- photodetachment
Water ion clusters
Unfocused laser
(H2O) 17-
Photodetachment
( neutral products )

17. in situ measurement of the volume effect probed with linear photodetachmentz
Turns out that its valuable to do this in situ since otherwise un-noticable self focusing in the entrance window can shift the focal point.
Ion beam

18. Calculated Peak Intensitiesz
Turns out that its valuable to do this in situ since otherwise un-noticable self focusing in the entrance window can shift the focal point.
Ion beam

19. linear photodetachment modeling of the volume effectz
Turns out that its valuable to do this in situ since otherwise un-noticable self focusing in the entrance window can shift the focal point.
Ion beam

20. 1st model system: SF6 + e- SF6- studies will be extended to
SF6 , H2O, and Ar based clusters

21. 1st model system: SF6 + e- U SF6 SF5- +F ~3eV SF6- ~1.1eV 1.57 Å
R ( S-F ) U
SF6-
SF6
1.73 Å
1.57 Å
SF5- +F
~3eV
~1.1eV

22. SF6- Energetics Neutral yield [a.u.] hv [eV] e-
Photodetachment efficiency curve (PDE) measurement with
tunable wavelength ns laser (in collaboration with Oded Heber WIS)
Neutral yield [a.u.]
hv [eV]
ΔEv ~ 0.1 eV

23. SF6- Energetics e-
Photodetachment efficiency curve (PDE) measurement with
tunable wavelength ns laser (in collaboration with Oded Heber WIS)
800 nm

24. SF6- non-linear photodetachment
~40 fs
800 nm
balance between peak intensity and volume effect (~2×1014 W/cm2 ) z
Ion beam

25. SF6- non-linear photodetachment @800nm
peak intensity (~6×1014 W/cm2 )

26. Can we remove more than one electron ?
3 Step model for intense field interaction with neutral species
(1)
(3)
And is this picture at all useful for anions ?

27. To remove the next electron we need >10 more photons
SF6 Dissociative Ionization data
Ion
AE (eV)
Method F+
37.5 ± 1.0 EI
FS+
30.5 ± 0.5
F2S+
27.0 ± 0.3
F3S+
18.79 ± 0.14 PI
F4S+
19.1 ± 0.5
F5S+
15.32 ± 0.04
NIST chemistry webbook
No one was able to observe a stable SF6+

28. Double detachment observed @ 5x1014 W/cm2

29. higher order processes –
double detachment
SF6- products @ I ≥ 1015 W/cm2
SIMION simulation
SF+
SF2-5+ S+ F+
SF6+
neutrals

30. higher order processes –
double detachment
SF6- products @ I ≥ 1015 W/cm2
SIMION simulation
add
1eV KER
SF+
SF2-5+ S+ F+
SF6+
neutrals

31. Polarization
F+ emitted along TOF axis

32. originate from Coulomb explosion events
Correlated F+ and S+
originate from Coulomb explosion events
Neutrals
RG background S+ F+ F+

33. Chirp effect ? F+
Neutrals

34. TOD effect ? F+
Neutrals

35. Polarization effect ?

36. Students: Non-linear detachment :Yishai Albeck PDE curve measurements: Itamar Luzon
Collaborations:
Oded Heber (Weizmann )
Ori Cheshnovsky (TAU)
Funding:
ERC
Legacy Heritage fund (מורשה)
EU PF7 people program (MC IRG)
Farks center for light induced processes
James Franck fund (light matter interactions)

37. M.Sc., Ph.D., and Postdoc positions available
Ultrafast Laser Pulses
Time Resolved Dynamics
Funding:
ERC
Legacy Heritage fund (מורשה)
EU PF7 people program (MC IRG)
Farks center for light induced processes
James Franck fund (light matter interactions)