1. 2D Momentum Spectra of the ATI Electrons by 10 fs Laser Pulses
Zhangjin Chen
Advisor: C. D. Lin
Collaborators:
Marlene Wickenhauser, A. T. Le and X. M. Tong
Department of Physics
Kansas State University

2. OUTLINE Introduction Theory Results Conclusions Background Motivation
Long range Coulomb potential effects
Intensity dependence for fixed wavelength
Conclusions

3. Background
laser pulse
ionization of electron
atom Ar
intensity

4. Background Keldysh parameter: Multiphoton ionization
Above-threshold-ionization (ATI)
Multiphoton ionization
Tunneling ionization

5. Background He Ar Bucksbaum et al: PRA 37, 3615(R) (1988)
Wickenhauser et al: PRA 73, (R) (2006) He Ar ħω
ATI peaks

6. Motivation
C.M. Marhajan, A. Alanser, ...,C.L. Cocke et al. (submitted)
atom
Low energy spectra: lots of structure even in tunneling regime

7. Theory Numerical solution of TDSE Strong field approximation (SFA)
Neglect: -Coulomb field on ionized electrons
-Depletion of ground state
-Other bound states
Single active electron approximation
Dipole transition moment
Split operator method for time propagation
Laser-dressed energy
X.M. Tong and Shih-I Chu: Chem Phys 217, 119 (1997)
M. Lewenstein et al: PRA 49, 2117 (1994)

8. Effects of Coulomb Potential

9. Effects of Coulomb Potential
Ip= eV
Exact TDSE
Ip= eV
TDSE for Rc=2
P (a.u.)
P (a.u.)
Ip= eV
TDSE for Rc=8
SFA
Ip= eV
TDSE for Rc=5
P|| (a.u.)
P|| (a.u.)

10. Effects of Coulomb Potential
Exact TDSE
TDSE for Rc=2
P (a.u.)
TDSE for Rc=8
SFA
P|| (a.u.)
P|| (a.u.)

11. Volume Effect x z y S Augst et al: J. Opt. Soc. Am. B 8, 858 (1991)
Rayleigh range of the focus z x y
Peak Laser Intensity
S Augst et al: J. Opt. Soc. Am. B 8, 858 (1991)

12. Intensity dependence P (a.u.) P|| (a.u.) P|| (a.u.) 600 nm, n=10

13. P (a.u.) P|| (a.u.) P|| (a.u.) Intensity dependence 600 nm, n=10

14. Conclusion Coulomb tail effects are crucial for slow photoelectrons
Volume effects has to be taken into account when compare theory with experiment

15. Thank You !

16. OUTLINE Introduction Theory Results Conclusions Background Motivation
Long range Coulomb potential effects
Wavelength dependence for fixed Keldysh parameter
Wavelength dependence for fixed 1st peak position
Intensity dependence for fixed wavelength
Conclusions

17. Background P (a.u.) P (arb units) P|| (a.u.) P|| (a.u.) P|| (a.u.)
Wickenhauser et al: PRA 73, (R) (2006)
Background
P (a.u.)
g ~ 1.76
g ~ 0.89
P (arb units)
P|| (a.u.)
P|| (a.u.)
P|| (a.u.)

18. Wavelength dependence for fixed
400 nm, n=7
600 nm, n=10
P (a.u.)
500 nm, n=9
700 nm, n=12
P|| (a.u.)
P|| (a.u.)

19. Wavelength dependence for fixed
400 nm, n=7
600 nm, n=11
P (a.u.)
500 nm, n=9
700 nm, n=13
P|| (a.u.)
P|| (a.u.)

20. Fixed Keldysh parameter
I λ Up Up+Ip γ n nһω p-1

21. Fixed 1st peak position
Intensity wavelength Up Up+Ip gamma n nw k first peak (eV)
Energy of photon= eV
Energy of photon= eV
Energy of photon= eV
Energy of photon= eV