Wavelength-dependence of Momentum-Space Images of Low-Energy Electrons Generated by

1. Wavelength-dependence of Momentum-Space Images of Low-Energy Electrons Generated by Short, Intense Laser Pulses at High Intensities Chakra Man Maharjan A S Alnaser, P Ranitiovic , I Litvinuyk and C L Cocke Department of Physics, Kansas State University 2006

2. MOTIVATION : To understand and resolve the energy and angular structure of the laser generated electrons in the low energy region

3. Parabolic mirror Supersonic jet Y Z Electron detector X Short pulse laser COLTRIMS Experimental Setup

4. Ionization In Laser field γ = Keldysh Parameter , Up ~ I λ2 γ >1 Multi photon process Ip = Ionization potential Up = Pondermotiv energy γ <1 Tunneling process

5. ATI Up=I/4ω2 n=∞ n=5 n=4 Freeman Resonance n=0 Freeman Resonance and Above Threshold Ionization (ATI) Intensity

6. 4p 4p 4p 4d 4d 4d 4f 4f 4f 5g 5g 5g 6g 6g 6g Freeman Resonance : sub-structures in ATI peaks

7. Density plot of the electron monenta along and perpendicular to the laser polarization for different wavelengths

8. Laser driven e ρ Kepler Hyperbola 0 Z Diffraction effect (GRT)

9. The same set of data in two different scale for 640nm.The upper panel is optimized to reveal weak features for large momenta, while the lower panel is optimized to show stronger low energy features 640nm 30v 18mw 640nm 30v 18mw main features only 640 nm low intensity features γ=0.54 7.08X1014 W/cm2 7.08X1014 W/cm2 Pt main features only 640 nm 7.08X1014 W/cm2 γ=0.54 Pz

10. γ=0.5 640 nm 8.2X1014 W/cm2 640nm 30v 18mw 640nm 30v 21mw 640nm 30v 10mw γ=0.54 640 nm 7.08X1014 W/cm2 Pt γ=0.72 640 nm 3.94X1014 W/cm2 Pz Comparison of the energy and angular structure with three different intensities for 640 nm

11. Plots of the energy spectra, integrated over all angles, in the region of the first ATI group

12. 0 10 20 30 40 50 60 70 80 90 640nm 640nm 400nm 0 10 20 30 40 50 60 70 80 90 Θ (deg) 590nm 680nm 0 10 20 30 40 50 60 70 80 90 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 E (eV) 800nm 615nm Energy Vs Angle

13. Projections of the data from energy spectrum onto the angle axis for a wavelength of 640 nm for selected energy slices 4f resonance 5g resonance The square of the Legendre polynomial P6(cosθ), multiplied by sinθ

14. Energy and angular structure of electrons in momentum image generated by a laser field from align N2 and 02 molecules

15. Delay Stage λ/4 Source chamber Detector chamber N2 KLS, VP PUMP – PROBE SETUP Pump Probe

16. Test of alignment of molecules (N2) N2+/N2+ Coulomb explosion Probe Pulse only With both Pump and Probe pulses

17. 1 N2 Ipump = 1.1 x1014 W/cm2 Iprobe=5.5X1014 W/cm2 2 1 2 Rotational revival ( N2)

18. Rotational revival 0.75 0.70 0.65 0.60 0.55 0.50 0.45 0.40 3600 3800 4000 4200 4400 4600 4800 5000 B 1 theta> N2 2 <cos 2 ATI STRUCTURES Delay(fs) 2 1

19. Rotational revival 1 N2 2 Photoelectron angular distribution 1 2

20. Ipump=4.0 x1013 W/cm2 Iprobe=1.0X1014 W/cm2 3100 fs 2920 fs Probe only O2

21. O2 ATI STRUCTURES Probe only 2920 fs 3100 fs

22. O2 Photoelectron angular distribution (5-6 eV) 2920 fs 3100 fs Probe only

23. Thanks for your attention !!