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Full-Text Articles in Physics

Attosecond Pulse Carrier-Envelope Phase Effects On Ionized Electron Momentum And Energy Distributions, Liang-You Peng, Anthony F. Starace Oct 2007

Attosecond Pulse Carrier-Envelope Phase Effects On Ionized Electron Momentum And Energy Distributions, Liang-You Peng, Anthony F. Starace

Anthony F. Starace Publications

We analyze carrier-envelope phase (CEP) effects on electron wave-packet momentum and energy spectra produced by one or two few-cycle attosecond xuv pulses. The few-cycle attosecond pulses are assumed to have arbitrary phases. We predict CEP effects on ionized electron wave-packet momentum distributions produced by attosecond pulses having durations comparable to those obtained by Sansone et al. [Science 314, 443 (2006)]. The onset of significant CEP effects is predicted to occur for attosecond pulse field strengths close to those possible with current experimental capabilities. Our results are based on single-active-electron solutions of the three-dimensional, time-dependent Schrödinger equation including atomic potentials appropriate ...


Polarization Control Of Direct (Non-Sequential) Two-Photon Double Ionization Of He, Evgeny A. Pronin, N. L. Manakov, S. I. Marmo, Anthony F. Starace Jul 2007

Polarization Control Of Direct (Non-Sequential) Two-Photon Double Ionization Of He, Evgeny A. Pronin, N. L. Manakov, S. I. Marmo, Anthony F. Starace

Anthony F. Starace Publications

An ab initio parametrization of the doubly-differential cross section (DDCS) for two-photon double ionization (TPDI) from an s2 subshell of an atom in a 1S0-state is presented. Analysis of the elliptic dichroism (ED) effect in the DDCS for TPDI of He and its comparison with the same effect in the concurrent process of sequential double ionization shows their qualitative and quantitative differences, thus providing a means to control and to distinguish sequential and non-sequential processes by measuring the relative ED parameter.


Thermal Entanglement Of Two Interacting Qubits In A Static Magnetic Field, G. Lagmago Kamta, Andrei Y. Istomin, Anthony F. Starace Jun 2007

Thermal Entanglement Of Two Interacting Qubits In A Static Magnetic Field, G. Lagmago Kamta, Andrei Y. Istomin, Anthony F. Starace

Anthony F. Starace Publications

We study systematically the entanglement of a two-qubit Heisenberg XY model in thermal equilibrium in the presence of an external arbitrarily-directed static magnetic field, thereby generalizing our prior work [G. Lagmago Kamta, A.F. Starace, Phys. Rev. Lett. 88, 107901 (2002)]. We show that a magnetic field having a component in the xy-plane containing the spin-spin interaction components produces different entanglement for ferromagnetic (FM) and antiferromagnetic (AFM) couplings. In particular, quantum phase transitions induced by the magnetic field-driven level crossings always occur for the AFM-coupled qubits, but only occur in FM-coupled qubits when the coupling is of Ising type or ...


Description Of Harmonic Generation In Terms Of The Complex Quasienergy. Ii. Application To Time-Dependent Effective Range Theory, M.V. Frolov, A.V. Flegel, N. L. Manakov, Anthony F. Starace Jun 2007

Description Of Harmonic Generation In Terms Of The Complex Quasienergy. Ii. Application To Time-Dependent Effective Range Theory, M.V. Frolov, A.V. Flegel, N. L. Manakov, Anthony F. Starace

Anthony F. Starace Publications

A formulation for the high-order harmonic generation (HHG) amplitude [M. V. Frolov et al., Phys. Rev. A 75, 063407 (2007), preceding paper] is employed to provide analytical results for HHG rates within our recently developed time-dependent effective range (TDER) theory (for time-dependent problems involving weakly bound electron systems). Exact and approximate (including quasiclassical) TDER HHG rates are employed to analyze the accuracy of common approximate methods for HHG calculations. For various specific negative ions with s and p outer electrons, numerical results for HHG spectra are presented over a wide interval of laser frequencies(extending from the tunneling to the ...


Description Of Harmonic Generation In Terms Of The Complex Quasienergy. I. General Formulation, M.V. Frolov, A.V. Flegel, N. L. Manakov, Anthony F. Starace Jun 2007

Description Of Harmonic Generation In Terms Of The Complex Quasienergy. I. General Formulation, M.V. Frolov, A.V. Flegel, N. L. Manakov, Anthony F. Starace

Anthony F. Starace Publications

Using the Hellmann-Feynman theorem for quasistationary quasienergy states of a quantum system in an intense laser field, we present the high-order harmonic generation (HHG) amplitude in terms of the complex quasienergy of a bound electron, thereby avoiding the necessity for an explicit form for the electron wave function in HHG calculations. This formulation for the HHG amplitude confirms use of the dual dipole moment (instead of the dipole moment expectation value) in wave-function-based HHG calculations in order to properly account for both the ionization and the Stark shift of the initial bound state in a strong laser field.


Threshold-Related Effects On The High Energy Plateau In Above-Threshold Detachment, Katarzyna Krajewska, Ilya I. Fabrikant, Anthony F. Starace Mar 2007

Threshold-Related Effects On The High Energy Plateau In Above-Threshold Detachment, Katarzyna Krajewska, Ilya I. Fabrikant, Anthony F. Starace

Anthony F. Starace Publications

We present results of a nonperturbative Floquet study of above-threshold detachment (ATD) of the H and F negative ions. Pronounced enhancements of ATD rates in the high-energy plateau region are found as the laser field intensity passes across ponderomotively shifted multiphoton thresholds. Depending on the symmetry of the initial state (s or p symmetry), the enhancement is found to be most pronounced for even- or odd-channel closures, which is consistent with threshold laws applicable at the closing of particular multiphoton channels. Variations of ATD photoelectron angular distributions as functions of laser intensity near multiphoton thresholds are also investigated.