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Strong-Field Imaging of Molecular Dynamics

Strong-Field Imaging of Molecular Dynamics. Wendell T. Hill, III University of Maryland Department of Physics and Institute for Physical Science and Technology. Explosion Energies. Heavy Atoms. Light Atoms. Cornaggia, et al ., PRA 44 , 4499 (1991). ~70% of E eq. ~40% of E eq.

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Strong-Field Imaging of Molecular Dynamics

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  1. Strong-Field Imaging of Molecular Dynamics Wendell T. Hill, III University of MarylandDepartment of Physics and Institute for Physical Science and Technology

  2. Explosion Energies Heavy Atoms Light Atoms Cornaggia, et al., PRA 44, 4499 (1991) ~70% of Eeq ~40% of Eeq Normand, et al., PRA 53, R1958 (1996)

  3. FR/2 Enhanced Ionization at Rc I R = Req R = Req R > Req Posthumus, et al. J.Phys.28; Zuo & Bandrauk, PRA 52; Seideman , et al. PRL 75

  4. Enhanced Ionization: Theory Numerical Integration of SE in 3D; Zuo and Bandrauk, PRA 52, R2511 (195) Manybody S-Matrix; J. Muth-Böhm, A. Becker and F. H. M. Faisal, ICOMP VIII (99)

  5. Theory Rc=4/IP (au) H2 Explosion Energy: Experiment Zuo and Bandrauk, PRA 52, R2511 (1995) Gibson, et al., PRL 79, 2022 (1997) Zhang and Hill, unpublished

  6. Emea 66 eV 3-Atom Enhanced Ionization at Rc RC  0.22 nm (4 au) nh + CO2 Op+ + Cq+ + Or+ No intermediate molecular states observed! p, q, r = 1,2,3

  7. GENERIC XY2 LINEAR POTENTIAL SURFACE R2 R1 Y+XY Y+X+Y XY+Y

  8. What about the electrons?

  9. Dynamic Screening Explosion Model Brewczyk, Rzążewski and Clark PRL 78, 191 (1997) Ionization and Dissociation InterlacedElectrons do not leave region immediately! Dissociation begins @ Req but slowed by electron cloud producing energies consistentwith dissociation from Rc. Hering, Brewczyk and Cornaggia, PRL 85, 2288 (2000)

  10. Thomas-Fermi Hydrodynamic Model

  11. Dynamic Screening Static Screening Static Screening Model - - - + + + - - O O C - Zhao, Zhang and Hill, PRA (submitted)

  12. Angular Dependence of EC

  13. Momentum & Time-of-Flight Spectra • Time-Resolved Images • 128 x 128 Pixels • 730 Hz Digital Acquisition • 500,000 – 1,000,000 Frames • Mass-Resolved • Energies & Angular Distributions Time-Resolved Waveforms Digital Scope Acquisition Mass-Resolved Energies Distributions

  14. 0 1 (a) H+ 110 – 210 ns (b) H2+ 210 – 310 ns (c) N3+ 320 – 420 ns (d) N3+ , O3+ 370 – 470 ns (e) N2+ 420 – 520 ns (f) N2+ , O2+ 470 – 570 ns (g) O2+ 520 – 620 ns (h) 570 – 670 ns (i) N+ 620 – 720 ns (j) N+ 670 – 770 ns (k) O+ 720 – 820 ns (l) O+ 770 – 870 ns (m) OH+ 820 – 920 ns (n) N2+,3+ , O2+,3+ 320 – 620 ns (o) All Ions All Time

  15. Momentum Image Momentum 0 0 Momentum POLARIZATION AXIS Scale: 5 – 8 amu/div

  16. SELECTIVE AVERAGE AVERAGE IMAGE 0 1 POLARIZATION AXIS Correlation Imaging

  17. NO2CO2 Symmetric Coulomb Explosion

  18. Through Minimum Across O-O Over-the-BarrierIonization

  19. I = 1.661014 , R = 0.302 nm, s = 0.0001 Limits on Smoothing Factor I = 1.75 1014 W/cm2, R = 0.294 nm, s = 0.03 I = 3.291014 W/cm2, R = 0.216 nm, s = 0.082

  20. Along Saddle Points Across O-O Bond EnhancedIonizationat Rc

  21. Symmetric Explosion vs. Bond Angle NO2CO2

  22. Charge Density Parameters NO2 CO2 e- e- e- e- Resulting Charge Distribution Wider Distribution Larger y0

  23. Linear vs. Bent Explosions CO2 explosion rangeb = 145 - 180° NO2 explosion rangeb = 125 - 170°

  24. Conclusion • The first example of where the Rc and screening models give different results! • Screening explains the electron dynamics and the differences between linear and bent explosions. • We have now recovered the ability to use ultrafast pulses to examine molecular structure.

  25. Support NSF Graduate Students Harry Zhao Vishal Chintawar J. Zhu Visitors G. Zhang (Tianjian) F. Adameitz (France) Acknowledgements • Undergraduates • T. Colvin, Jr. • D. Cofield • D. Ellingston

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