Molecular Tunneling Ionization and Molecular Alignment

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Molecular Tunneling Ionization and Molecular
Alignment
X. M. Tong, Z. X. Zhao and C. D. Lin Physics
Department, Kansas State University, Manhattan KS
66506
email xmtong_at_phys.ksu.edu
http//phys.ksu.edu/xmtong
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Molecular Tunneling Ionization

• Motivation
• Ionization tunneling multiphoton
• ADK (Ammosov, Delone and Krainov) model
• Experimental observations.
• Theoretical Method
• Molecular orbital at asymptotical region
• Tunneling ionization
• How to compare with experiments?
• Results and Discussion
• D2/Ar, N2/Ar, O2/Xe, CO/Kr
• S2/Xe, SO/Xe, NO/Xe
• F2/Ar

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Atoms or Molecules in an Intense Laser Field
Multiphoton Ionization
Tunneling Ionization

Keldysh parameter
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Ionization of N2 and Ar
Ip N2 15.58 eV Ar 15.76 eV
30 fs Guo et al., PRA 58 (1998) R4271. 100
fs DeWitt et al., PRL 87 (2001) 153001.
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Ionization of O2 and Xe
Ip O2 12.36 eV Xe 12.13 eV
Ionization supression
Interference Model Muth-Bohm et al., PRL 85
(2000) 2280. Failed for D2, F2 Effective
Charge Guo, PRL 85 (2000) 2276.
30 fs Guo et al., PRA 58 (1998) R4271. 200
fs Talebpour et al., JPB 29 (1996) L677.
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Atomic Tunneling Ionization
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Atomic Tunneling Ionization
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Atomic Tunneling Ionization
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Molecular Tunneling Ionization
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Molecular Tunneling Ionization
A1
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Ionization Rates of H2 in a Static Field
H2
z
F
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Ionization Rates of H2
H2
Saenz, PRA 61(2000) 051402.
z
F
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Ratio of Ionization Rates for N2Ar and O2Xe
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30 fs Guo et al., PRA 58 (1998) R4271. 100
fs DeWitt et al., PRL 87 (2001) 153001.
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30 fs Guo et al., PRA 58 (1998) R4271. 200
fs Talebpour et al., JPB 29 (1996) L677.
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Tunneling Ionization for Oriented Molecules
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Ionization for Oriented N2 Molecules
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Ionization for Oriented O2 Molecules
q
F
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How to Compare with Experiments ?
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Ionization Rate, Probability and Signal
D2/Ar
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Molecular Vibration Effect
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N2/Ar
Ip N2 15.58 eV Ar 15.76 eV
30 fs Guo et al., PRA 58 (1998) R4271. 100
fs DeWitt et al., PRL 87 (2001) 153001.
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O2/Xe
Ip O2 12.36 eV Xe 12.13 eV
30 fs Guo et al., PRA 58 (1998) R4271. 200
fs Talebpour et al., JPB 29 (1996) L677.
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D2/Ar
Ip D2 15.470.8 eV Ar 15.76 eV
Expt Wells et al., PRA 66 (2002) 013409.
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CO/Kr
Ip CO 14.01 eV Kr 14.00 eV
Expt Wells et al., PRA 66 (2002) 013409.
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F2/Ar
Ip F2 15.70 eV Ar 15.76 eV
Expt 100 fs DeWitt et al., PRL 87 (2001)
153001.
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NO/Xe, S2/Xe and SO/Xe
Ip NO 9.26 eV S2 9.36 eV SO 10.29
eV Xe 12.13 eV
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NO and Xe
Expt Wells et al., PRA 66 (2002) 013409. Xe
Expt Guo et al., PRA 58 (1998) R4271.
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S2 and Xe
Expt Wells et al., PRA 66 (2002) 013409. Xe
Expt Guo et al., PRA 58 (1998) R4271.
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SO and Xe
Expt Wells et al., PRA 66 (2002) 013409. Xe
Expt Guo et al., PRA 58 (1998) R4271.
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Summary
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Summary

• Develop a molecular tunneling ionization theory
• Study the diatomic molecular ionization
• Extend to triatomic molecules
• Different suppression mechanisms.

The full paper can be downloaded
from http//www.phys.ksu.edu/xmtong/pub.html
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(2) Molecular Alignment
(a) Angular dependent ionization signal (b) How
to Align a molecule.
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Molecular Alignment in laser field
J. Ortigoso et al., JCP110,3870
Short pulse revival Long pulse No
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Molecular Alignment
Revival
Initial Random
Kick Deposit J
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Molecular Alignment
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Molecular Alignment
O2 Wjm 1 (even J) or 0 (odd J) N2 Wjm 1/3
(even J) or 2/3 (odd J)
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Kick or Push ?
F Dt
Pulse intensity 2x1013 W/cm2
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N2 (2x1013 8x1013)
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Revival
O2 (2x1013 4x1013)
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Summary

1. Optimized revival can be achieved with a fixed
   laser intensity
2. 10 to 20 enhancement for O2, and
3. 20 to 60 enhancement for N2
4. maximum enhancement when the two field parallel.

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Atomic and Molecular Data
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Molecular Data
hw 1.57 eV
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Alignment Effects
Aligned along the field vs. average
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Summary