Laser Assisted Charge transfer in He H Collisions

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Laser Assisted Charge transfer in He H
Collisions
Presented by Fatima Anis Dr. Brett D. Esry V.
Roudnev R. Cabrera-Trujillo
Dr. Ben-Itzhak Dr. Cocke
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Introduction

• Does presence of a Laser Field affect charge
  transfer?
• nh? a H ? He p
• How much does it affect?
• Can we control charge transfer during collision
  through CE phase?
• Possibility for doing such an experiment

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What has been done?
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Theory

• Collision Geometry
• Method
• What are we solving?
• How are we solving?
• Calculations Parameters
• Calculation of charge transfer probability

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Collision scheme

• Collision Energy 1keV/amu
• Laser parameters
• Intensity 3.5x1012W/cm2
• FWHM 6.0fs
• ? 800nm
• f is CEP

! Capture is possible for almost 1-2 optical
cycles
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What are we solving?

• We are solving 3D Time Dependent Schrödinger
  Equation

with

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How are we solving? Crank-Nicholson method

• Relaxation Method to get the ground state of
  Hydrogen

• Our lattice solution utilizes a uniform grid and
  three-point finite-difference method

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Calculation parameters
Time Step 0.06 a.u. Time Range ti - 200.0
a.u. to tf 200.0 a.u. Projectile Velocity
0.1 a.u. xinitial(b,0,-20.0) ? xfinal(b,0,20.0)
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Calculating Charge Transfer Probability
We estimate the reaction probability by
integrating the electron density function around
a box OT surrounding the target at tf
Where,
We define OT as OT -4, 15x x -4, 4y x -25,
10z a.u.
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Testing

• The time step of 0.06 a.u. ensures energy
  conservation within 0.7 of its initial value
• No Soft Core by making sure our vector lies
  exactly between the two grid points
• Comparison with other results
• END
• Kirchners

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Testing

• No Laser Field
• Collision Energy 2keV/amu

Reference T.Kirchner, PRL 89, 093203 (2002) T.
Kirchner, PRA 69, 063412 (2004)
Fig. He H charge transfer probability as a
function of b with no Laser Field for projectile
energy of 2keV/amu.
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Testing
Fig. HeH weighted transfer probability as a
function of b for Eo 0.0 a.u. and collision
energy 1 keV/amu
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Results
Collision scheme

• Parallel Polarization Result
• Perpendicular polarization

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Parallel PolarizationComparison of END Grid
Calculation
Fig. HeH weighted Laser induced charge
transfer probability as a function b for
collision energy 1keV/amu, E0 0.01a.u. and CEP
- p/2
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Parallel Polarization
s(a.u.2) Field Free 0.95 E0
0.01a.u. CEPp 5.83 CEP3p/2 4.58 CEP Averaged
5.28
Fig. He H weighted charge transfer
probability as a function of b for collision
energy of 1keV/amu
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Parallel Polarization
Fig. Charge transfer total cross section as a
function of CEP for a collision energy 1keV/amu
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Perpendicular Polarization
s(a.u.2) Field Free 0.95 E0 0.01a.u. a
0.0 8.35 a p/5 5.61 a 2p/5 1.83 Total
4.66
Fig. CEP-Averaged weighted charge transfer
probability as a function of b for different
orientation of the laser field and collision
plane
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Perpendicular Polarization
Fig. CEP-Averaged cross section as a function the
relative angle a
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Perpendicular Polarization
Fig. Capture cross section as a function of CEP
for different orientations of the laser field and
the collision plane
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Without Field
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With Laser Field
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Conclusion

• 4-5 fold enhancement in capture cross section in
  case of both parallel and perpendicular Laser
  polarization
• Enhancement is CEP dependent for parallel and
  perpendicular Laser polarizations
• For Parallel polarization capture cross section
  is enhanced significantly independent of CEP
• For perpendicular polarization effect of CEP and
  relative angle a are related to each other.

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Thank You