983 research outputs found
A 4-Component Dirac Theory of Ionization of Hydrogen Molecular Ion in a Super-Intense Laser Field
In this paper a 4-component Dirac theory of ionization of hydrogen molecular
ion in a super-intense laser field is developed. Simple analytic expressions
for the spin specific as well as the total ionization currents emitted from the
ground state of the ion are derived. The results are given for all polarization
and finite propagation vectors of the field. They apply for inner-shell
ionization of analogous heavier molecular ions as well. The presence of
molecular two-slit interference effect, first found in the non-relativistic
case, and the spin-flip ionization current, and an asymmetry of the up- and
down-spin currents similar to that predicted in the atomic case, are found also
to hold for the present relativistic molecular ionic case. Finally, the
possibility of controlling the dominant spin currents by selecting the
handedness of a circularly polarized incident laser field is pointed out.Comment: 7 pages, no figure
Interplay of polarization geometry and rotational dynamics in high harmonic generation from coherently rotating linear molecule
Recent reports on intense-field pump-probe experiments for high harmonic
generation from coherently rotating linear molecules, have revealed remarkable
characteristic effects of the simultaneous variation of the polarization
geometry and the time delay on the high harmonic signals. We analyze the
effects and give a unified theoretical account of the experimental observationsComment: 4 pages, 5 figure
Multiphoton excitations in vibrational rotational states of diatomic molecules in intense electromagnetic field
A theory is presented and a calculational procedure is outlined for evaluating transition amplitudes of multiphoton excitations of vibrational-rotational levels in diatomic molecules. This theory can be utilized in studying behavior of molecules in intense electromagnetic fields
Vibro-rotational excitations of H2/+/ by e/+/ impact - A semi-classical approach
Semiclassical approach to vibrorotational excitations of H2/+/ by positron impac
Geometric phases in open tripod systems
We first consider stimulated Raman adibatic passages (STIRAP) in a closed
four-level tripod system. In this case, the adiabatic eigenstates of the system
acquire real geometric phases. When the system is open and subject to
decoherence they acquire complex geometric phases that we determine by a Monte
Carlo wave function approach. We calculate the geometric phases and the state
evolution in the closed as well as in the open system cases and describe the
deviation between these in terms of the phases acquired. When the system is
closed, the adiabatic evolution implements a Hadamard gate. The open system
implements an imperfect gate and hence has a fidelity below unity. We express
this fidelity in terms of the acquired geometric phases.Comment: 10 pages 7 figure
Attosecond probing of instantaneous AC Stark shifts in helium atoms
Based on numerical solutions of the time-dependent Schr\"odinger equation for
either one or two active electrons, we propose a method for observing
instantaneous level shifts in an oscillating strong infrared (IR) field in
time, using a single tunable attosecond pulse to probe excited states of the
perturbed atom. The ionization probability in the combined fields depends on
both, the frequency of the attosecond pulse and the time delay between both
pulses, since the IR field shifts excited energy levels into and out of
resonance with the attosecond probe pulse. We show that this method (i) allows
the detection of instantaneous atomic energy gaps with sub-laser-cycle time
resolution and (ii) can be applied as an ultrafast gate for more complex
processes such as non-sequential double-ionization
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