Krzysztof Sacha

Self-localized impurities embedded in a one dimensional Bose-Einstein condensate and their quantum fluctuations (2006)

Building on insights about the classical pathways to double ionization in strong laser fields we here propose a 1+1-dimensional model that captures essentials of the 3-d potential landscape and...

Sacha, Krzysztof, Timmermans, Eddy

We consider the self-localization of neutral impurity atoms in a Bose-Einstein condensate in a 1D model. Within the strong coupling approach, we show that the self-localized state exhibits parametric...

Images of a Bose-Einstein condensate in position and momentum space (2005)

N-particle Bogoliubov vacuum state (2005)

In the Bogoliubov theory a condensate initially prepared in its ground state described by stationary Bogoliubov vacuum and later perturbed by a time-dependent potential or interaction strength...

Images of a Bose-Einstein condensate: diagonal dynamical Bogoliubov vacuum (2005)

We consider the Bogoliubov vacuum state in the number-conserving Bogoliubov theory proposed by Castin and Dum [Phys. Rev. A 57, 3008 (1998)]. We show that in the particle representation the vacuum...

Non-sequential double ionization of molecules in a strong laser field (2004)

Evolution of a Bose-Einstein condensate subject to a time-dependent external perturbation can be described by a time-dependent Bogoliubov theory: a condensate initially in its ground state Bogoliubov...

Prauzner-Bechcicki, Jakub S., Sacha, Krzysztof, Eckhardt, Bruno

We consider the final stage of double ionization of $\rm O_2$ molecules by short linearly polarized laser pulses. The saddles of the effective adiabatic potential energy close to which simultaneous...

Soliton in BCS superfluid Fermi gas (2004)

Non-sequential double ionization of molecules (2004)

We analyze a superfluid state of two species gas of fermions trapped in a quasi-1D harmonic potential and interacting via attractive s-wave collisions. It is shown that the gap equation posesses a...

Prauzner-Bechcicki, Jakub S., Sacha, Krzysztof, Eckhardt, Bruno, Zakrzewski, Jakub

Double ionization of diatomic molecules by short linearly polarized laser pulses is analyzed. We consider the final stage of the ionization process, that is the decay of a highly excited two electron...

Pathways to non-sequential multiple ionization in strong laser fields (2003)

Condensate Heating by Atomic Losses (2003)

The outgoing electrons in non-sequential multiple ionization in intense laser fields are strongly correlated. The correlations can be explained within a classical model for interacting electrons in...

Images of the Dark Soliton in a Depleted Condensate (2002)

Atomic Bose-Einstein condensate is heated by atomic losses. Predicted depletion ranges from 1% for a uniform 3D condensate to around 10% for a quasi-1D condensate in a harmonic trap.

Dziarmaga, Jacek, Karkuszewski, Zbyszek P., Sacha, Krzysztof

The dark soliton created in a Bose-Einstein condensate becomes grey in course of time evolution because its notch fills up with depleted atoms. This is the result of quantum mechanical calculations...

The Bogoliubov Theory of a BEC in Particle Representation (2002)

Manipulating the shape of electronic non-dispersive wave-packets in the hydrogen atom: numerical tests in realistic experimental conditions (2002)

In the number-conserving Bogoliubov theory of BEC the Bogoliubov transformation between quasiparticles and particles is nonlinear. We invert this nonlinear transformation and give general expression...

Delande, Dominique, Sacha, Krzysztof, Zakrzewski, Jakub

We show that combination of a linearly polarized resonant microwave field and a parallel static electric field may be used to create a non-dispersive electronic wavepacket in Rydberg atoms. The...

Stirring Bose-Einstein condensate (2002)

Damski, Bogdan, Sacha, Krzysztof, Zakrzewski, Jakub

By shining a tightly focused laser light on the condensate and moving the center of the beam along the spiral line one may stir the condensate and create vortices. It is shown that one can induce...

Changes of the topological charge of vortices (2002)

Damski, Bogdan, Sacha, Krzysztof

We consider changes of the topological charge of vortices in quantum mechanics by investigating analytical examples where the creation or annihilation of vortices occurs. In classical hydrodynamics...

Greying of the Dark Soliton: Depletion in the Anomalous Mode of the Bogoliubov Theory (2002)

Collective excitation of trapped degenerate Fermi gases (2001)

Quantum depletion from an atomic quasi one dimensional Bose-Einstein condensate with a dark soliton is studied in a framework of the Bogoliubov theory. Depletion is dominated by an anomalous mode...

Damski, Bogdan, Sacha, Krzysztof, Zakrzewski, Jakub

We show that the slow driving of a focused laser beam through the cloud of trapped cold fermions allows for a creation of the collective excitation in the system. The method, proposed originally by...

Quantum Depletion of an Excited Condensate (2001)

Dziarmaga, Jacek, Karkuszewski, Zbyszek P., Sacha, Krzysztof

We analyze greying of the dark soliton in a Bose-Einstein condensate in the limit of weak interaction between atoms. The condensate initially prepared in the excited dark soliton state is loosing...

Wannier threshold law for two electron escape in the presence of an external electric field (2001)

Mean field loops versus quantum anti-crossing nets in trapped Bose-Einstein condensates (2001)

We consider double ionization of atoms or ions by electron impact in the presence of a static electric field. As in Wanniers analysis of the analogous situation without external field the dynamics...

Karkuszewski, Zbyszek P., Sacha, Krzysztof, Smerzi, Augusto

We study a Bose-Einstein condensate trapped in an asymmetric double well potential. Solutions of the time-independent Gross-Pitaevskii equation reveal intrinsic loops in the energy (or chemical...

Non-sequential triple ionization in strong fields (2001)

Simple method for excitation of a Bose-Einstein condensate (2001)

We consider the final stage of triple ionization of atoms in a strong linearly polarized laser field. We propose that for intensities below the saturation value for triple ionization the process is...

Damski, Bogdan, Karkuszewski, Zbyszek P., Sacha, Krzysztof, Zakrzewski, Jakub

An appropriate, time-dependent modification of the trapping potential may be sufficient to create effectively collective excitations in a cold atom Bose-Einstein condensate. The proposed method is...

Driven Rydberg atoms reveal quartic level repulsion (2001)

A method for collective excitation of Bose-Einstein condensate (2001)

The dynamics of Rydberg states of a hydrogen atom subject simultaneously to uniform static electric field and two microwave fields with commensurate frequencies is considered in the range of small...

Karkuszewski, Zbyszek P., Sacha, Krzysztof, Zakrzewski, Jakub

It is shown that by an appropriate modification of the trapping potential one may create collective excitation in cold atom Bose-Einstein condensate. The proposed method is complementary to earlier...

Driven Rydberg Atoms Reveal Quartic Level Repulsion (2001)

Classical analysis of correlated multiple ionization in strong fields (2000)

Pathways to double ionization of atoms in strong fields (2000)

We discuss the final stages of the simultaneous ionization of two or more electrons due to a strong laser pulse. An analysis of the classical dynamics suggests that the dominant pathway for...

Multielectron ionization of atoms in strong fields: Classical analysis in symmetric subspace (2000)

We discuss the final stages of double ionization of atoms in a strong linearly polarized laser field within a classical model. We propose that all trajectories leading to non-sequential double...

Classical double ionization of atoms in strong fields (2000)

We consider the final stage of multiple ionization of atoms in a strong linearly polarized laser field within a classical model. We propose that non-sequential multiple ionization is dominated by...

Non-resonant driving of H atom with broken time-reversal symmetry (2000)

Recent high resolution measurements of the momenta of two electrons emitted from Argon atoms in a strong laser field show a strong preference for the outgoing electrons to have similar momenta and to...

Sacha, Krzysztof

The dynamics of atomic hydrogen placed in a static electric field and illuminated by elliptically polarized microwaves is studied in the range of small field amplitudes where perturbation...

Breaking time reversal symmetry in chaotic driven Rydberg atoms (2000)

Sacha, Krzysztof, Zakrzewski, Jakub, Delande, Dominique

We consider the dynamics of Rydberg states of the hydrogen atom driven by a microwave field of elliptical polarization, with a possible additional static electric field. We concentrate on the effect...

Chaotic Rydberg atoms with broken time-reversal symmetry (1999)

Sacha, Krzysztof, Zakrzewski, Jakub, Delande, Dominique

The dynamics of Rydberg states of atomic hydrogen perturbed simultaneously by a static electric field and a resonant microwave field of elliptical polarization is analysed in the quantum perturbative...

Resonant dynamics of the H atom in an elliptically polarized microwave field (1998)

H atom in elliptically polarized microwaves: Semiclassical versus quantum resonant dynamics (1998)

The dynamics of Rydberg states of atomic hydrogen driven by elliptically polarized microwaves of frequency fulfilling 2:1 classical resonance condition is investigated both semiclassically and...