New features of interaction of atomic and molecular systems with intense ultrashort laser pulses

Abstract

New important physics of laser -atom interaction is found out and discussed in the case of ultrashort duration of lowfrequency laser pulses. Several types of interference effects are observed during strong-field atomic ionization and further rescattering and are found to arise due to wide momentum and angular distribution of the electron formed in the continuum. The found interference effects are shown to play an important role in the formation of the electron angular and momentum distribution, strong left -right asymmetry of the electron ejection, observed carrier-envelope phase (CEP) effects and formation of the lowenergy electrons in continuum. In addition, the arising new features of atomic dynamics in a strong field are confirmed to take place in a quasistatic regime of ionization in the case of middle IR laser frequency. The 2D momentum distribution of photoelectron in the continuum calculated in the strong-field ionization of 3D Hydrogen atom by four cycle laser pulse (2-0-2) with peak laser intensity 1.5×10

Ionization with low-frequency fields in the tunneling regime

“…Comparison of SFA, which neglects the ion's Coulomb field, with ab-initio calculations supported the assumption of the ion's Coulomb field as responsible for the modification of electron trajectories191011121314151617. Direct tunneling close to a local field maximum, even though resulting in low-energy photoelectrons (until 2 U p ; ponderomotive energy U p = E 2 /4ω 2 ; E is the peak electric field amplitude and ω the laser frequency in atomic units), is therefore seen as an unlikely cause of the LES.…”

Momentum Distribution of Near-Zero-Energy Photoelectrons in the Strong-Field Tunneling Ionization in the Long Wavelength Limit

“…Although from many aspects, including quantum and semiclassical, numerous theoretical investigations12131415161718192021 of the underlying physics of LES were reported, the controversies on the surprising structure have been continuing. In the above experiments, the photoelectrons were detected only within a small solid angle around the laser polarization direction by a time-of-flight spectrometer.…”

Non-perturbative approach to bosonic multi-pair creation in arbitrary external fields

“…In fact, the role alternating fields play appears to be similar to that of laser ioniza tion in atoms and molecules [15][16][17][18]. Once the fre quency of the alternating field is greater than the gap between positive and negative energy bands it can break down the vacuum to produce permanent pairs even for intensities that are subcritical.…”