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Strong-Field Atomic Physics
Atoms
Infrared wavelength
Short pulse duration
High intensity
Linear-polarized
ions or
electrons
Laser
or high-order
harmonics
Strong-Field Atomic Physics
I
The electron can
tunnel through the
distorted Coulomb
barrier
Interaction with the core
III
III
The electron wave packet
interacts with the remaining
core
•Rescattered electrons
•Multiple ionization
•High-order harmonic generation
II
The electron is accelerated
by the field, and may return
to the atomic core
Electromagnetic
field
Electron trajectories
Time
Time
High kinetic
energy electrons
Non-sequential
ionization
High-order
harmonic
generation
IP
Electron energy
High kinetic energy electrons: Above-Threshold-Ionization
Multi-electron emission: Non-sequential Ionization
He++
He+
Ion signal
780 nm
100 fs
He
Laser intensity
High-Order Harmonic Generation in Gases
3
5
7
(2q  1)
H37
Photons
.
.
Plateau
Cut-off
H43
H31
H49
H53
50
III
60
70
Energy (eV)
80
The electron recombines with the atom,
emitting its energy as an XUV photon
High-Order Harmonic Generation in Gases
Laser
Atomic
Medium
Gas cell
with rare
gas
Titanium-Sapphire, 800 nm
1 kHz, 2 mJ, 35 fs pulses
Tunneling
Acceleration in the
continuum
Recombination
Time
Time
Attosecond pulse
train
Harmonic spectrum

Attosecond pulse train

0
20
Frequency domain
Time domain

L

2L
Energy
Harmonic spectrum
=20eV
2

Time
Attosecond pulse train
2 200
as

Energy
Broad spectrum
Time
Single attosecond pulse
Energy
Is this always true?
Time
Characterization of attosecond pulses
in a train: RABITT technique
Photoelectron spectrum
Ip
The sideband signal depends on
 q2   q
Generation of short light pulses