Wavelength-dependence of Momentum-Space Images

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
Experimental Setup
4
Ionization In Laser field
Ip Ionization potential Up Pondermotiv energy
? lt1
Tunneling process
5
Freeman Resonance and Above Threshold Ionization
(ATI)
Intensity
6
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
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

10
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
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(cos?),
multiplied by sin?
14
Energy and angular structure of electrons in
momentum image generated by a laser field from
align N2 and 02 molecules
15
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
Rotational revival ( N2)
18
Rotational revival

B
1
thetagt
N2
2

ltcos
2
ATI STRUCTURES
Delay(fs)
2
1
19
Rotational revival
1
N2
2
Photoelectron angular distribution
1
2
20
O2
21
O2
ATI STRUCTURES
2920 fs
3100 fs
Probe only
22
O2
Photoelectron angular distribution (5-6 eV)
2920 fs
3100 fs
Probe only
23
Thanks for your attention !!