molecular tunneling ionization and molecular alignment

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@phys.ksu.edu http://phys.ksu.edu/~xmtong

• 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

Molecular Tunneling Ionization

Tunneling Ionization

Multiphoton Ionization:

Keldysh parameter

Atoms or Molecules in an Intense Laser Field

Ionization of N2 and Ar

30 fs: Guo et al., PRA 58 (1998) R4271. 100 fs : DeWitt et al., PRL 87 (2001) 153001.

Ip

N2: 15.58 eVAr: 15.76 eV

30 fs: Guo et al., PRA 58 (1998) R4271. 200 fs : Talebpour et al., JPB 29 (1996) L677.

Interference Model:Muth-Bohm et al., PRL 85 (2000) 2280.Failed for D2, F2

Effective Charge:Guo, PRL 85 (2000) 2276.

Ip

O2: 12.36 eVXe: 12.13 eV

Ionization of O2 and Xe

Ionization supression

W.P.T.I.

Atomic Tunneling Ionization

Atomic Tunneling Ionization

Atomic Tunneling Ionization

W.P.T.I.

F

Molecular Tunneling Ionization

A1A2

A3

Molecular Tunneling Ionization

3.5x1014 W/cm2

Ionization Rates of H2+ in a Static Field

F

H2+

z

Saenz, PRA 61(2000) 051402.

Ionization Rates of H2

F

H2

z

Ratio of Ionization Rates for N2:Ar and O2:Xe

F

Tunneling Ionization for Oriented Molecules

X1013 W/cm2

Ionization for Oriented N2 Molecules

X1013 W/cm2

F

Ionization for Oriented O2 Molecules

z

r

How to Compare with Experiments ?

D2/Ar

Ionization Rate, Probability and Signal

D2 Energy Potential

Molecular Vibration Effect

30 fs: Guo et al., PRA 58 (1998) R4271. 100 fs : DeWitt et al., PRL 87 (2001) 153001.

N2/Ar

Ip

N2: 15.58 eVAr: 15.76 eV

30 fs: Guo et al., PRA 58 (1998) R4271. 200 fs : Talebpour et al., JPB 29 (1996) L677.

O2/Xe

Ip

O2: 12.36 eVXe: 12.13 eV

Expt: Wells et al., PRA 66 (2002) 013409.

Ip

D2: 15.47+0.8 eVAr: 15.76 eV

D2/Ar

Expt: Wells et al., PRA 66 (2002) 013409.

Ip

CO: 14.01 eVKr: 14.00 eV

CO/Kr

Expt: 100 fs : DeWitt et al., PRL 87 (2001) 153001.

Ip

F2: 15.70 eVAr: 15.76 eV

F2/Ar

Ip

NO: 9.26 eVS2: 9.36 eVSO: 10.29 eVXe: 12.13 eV

NO/Xe, S2/Xe and SO/Xe

Expt: Wells et al., PRA 66 (2002) 013409.Xe Expt: Guo et al., PRA 58 (1998) R4271.

NO and Xe

Expt: Wells et al., PRA 66 (2002) 013409.Xe Expt: Guo et al., PRA 58 (1998) R4271.

S2 and Xe

Expt: Wells et al., PRA 66 (2002) 013409.Xe Expt: Guo et al., PRA 58 (1998) R4271.

SO and Xe

A1A2

A3

Summary

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

Summary

The full paper can be downloaded fromhttp://www.phys.ksu.edu/~xmtong/pub.html

(2) Molecular Alignment

Fq

(a) Angular dependent ionization signal; (b) How to Align a molecule.

Molecular Alignment in laser field

J. Ortigoso et al., JCP110,3870

Short pulse: revival;Long pulse: No

Molecular Alignment

Initial: Random Kick:

Deposit J

Revival:

Molecular Alignment

F

Molecular Alignment

O2: Wjm = 1 (even J) or 0 (odd J)N2: Wjm = 1/3 (even J) or 2/3 (odd J)

Kick or Push ?

Pulse intensity 2x1013 W/cm2

F t

N2: (2x1013 : 8x1013)

Revival

O2: (2x1013 : 4x1013)

Summary

(a) Optimized revival can be achieved with a fixed laser intensity;(b) 10% to 20% enhancement for O2, and(c) 20% to 60% enhancement for N2;(d) maximum enhancement when the two field parallel.

Summary