Multiphoton processes in an intense laser field. V. The high-frequency regime

Dörr, Martin; Potvliege, R. M.; Proulx, Daniel; Shakeshaft, Robin

doi:10.1103/physreva.43.3729

Cited by 122 publications

(68 citation statements)

References 30 publications

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“…This allows the electron dynamics to be described by an effective potential that, on average, localizes the electron away from the vicinity of the nucleus. Subsequent ab initio Floquet calculations confirmed that ionization rates decrease with increasing intensity in a high-frequency field [3]. By directly integrating the time-dependent Schrödinger equation numerically, simulations in one [4] and three dimensions [5] demonstrated reductions in the ionization probability with increasing laser intensity when an atom interacts with realistic laser pulses having a finite duration.…”

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confidence: 84%

Breakdown of Stabilization of Atoms Interacting with Intense, High-Frequency Laser Pulses

et al. 2000

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An analysis of the influence of the magnetic field of an intense, high-frequency laser pulse on the stabilization of an atomic system is presented. We demonstrate that at relatively modest intensities the magnetic field can significantly alter the dynamics of the system. In particular, a breakdown of stabilization occurs, thereby restricting the intensity regime in which the atom is relatively stable against ionization. Counterpropagating pulses do not negate the detrimental effects of the magnetic field. We compare our quantum mechanical results with classical Monte Carlo simulations. PACS numbers: 32.80.Fb, 32.80.Rm, 42.50.Hz Theoretical studies of atoms interacting with highfrequency intense laser pulses have predicted a significant decrease in the ionization probability with increasing laser intensity. This phenomenon is referred to as atomic stabilization, and has been extensively studied over the past decade [1]. Many aspects of this phenomenon can be understood by performing a Kramers-Henneberger (KH) transformation to the rest frame of a classical electron in the laser field. In particular, by developing a highfrequency Floquet theory in the KH frame [2], stabilization can be seen to have its origin in the rapid quiver motion of the atomic electron in the laser field. This allows the electron dynamics to be described by an effective potential that, on average, localizes the electron away from the vicinity of the nucleus. Subsequent ab initio Floquet calculations confirmed that ionization rates decrease with increasing intensity in a high-frequency field [3]. By directly integrating the time-dependent Schrödinger equation numerically, simulations in one [4] and three dimensions [5] demonstrated reductions in the ionization probability with increasing laser intensity when an atom interacts with realistic laser pulses having a finite duration. Further work has been carried out in order to elucidate the effects of the pulse shape and duration [6,7]. We also note that evidence of atomic stabilization of Rydberg states has been observed experimentally [8].In the above-mentioned theoretical studies, the magnetic component of the laser pulse was neglected. However, as the laser intensity increases, relativistic effects that alter the stabilization dynamics become important. Classical Monte Carlo simulations have indicated that the magnetic field pushes the electron in the laser pulse propagation direction, reducing the degree of stabilization [9]. Relativistic wave equations have also been considered within the context of reduced dimensional models [10,11]. However, it is also of interest to study the effects that are neglected in the dipole approximation by using the fully space-and time-dependent vector potential in the nonrelativistic Schrödinger equation [12]. For atomic hydrogen, this results in the cylindrical symmetry of the system being broken, thereby requiring a fully three-dimensional calculation to be carried out for extremely high laser intensities. This is a computationally demanding task. Howev...

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Breakdown of Stabilization of Atoms Interacting with Intense, High-Frequency Laser Pulses

et al. 2000

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“…and ε 0 > 8 a.u. This is the well-known strong-field atomic stabilization phenomenon [66][67][68][69][70][71][72]. This phenomenon can occur at any frequency and can be enhanced by relativistic effects [70].…”

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confidence: 99%

Precision calculation of above-threshold multiphoton ionization in intense short-wavelength laser fields: The momentum-space approach and time-dependent generalized pseudospectral method

Zhou

Chu

2011

Phys. Rev. A

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We present an approach in momentum (P) space for the accurate study of multiphoton and above-threshold ionization (ATI) dynamics of atomic systems driven by intense laser fields. In this approach, the electron wave function is calculated by solving the P-space time-dependent Schrödinger equation (TDSE) in a finite P-space volume under a simple zero asymptotic boundary condition. The P-space TDSE is propagated accurately and efficiently by means of the time-dependent generalized pseudospectral method with optimal momentum grid discretization and a split-operator time propagator in the energy representation. The differential ionization probabilities are calculated directly from the continuum-state wave function obtained by projecting the total electron wave function onto the continuum-state subspace using the projection operator constructed by the continuum eigenfunctions of the unperturbed Hamiltonian. As a case study, we apply this approach to the nonperturbative study of the multiphoton and ATI dynamics of a hydrogen atom exposed to intense shortwavelength laser fields. High-resolution photoelectron energy-angular distribution and ATI spectra have been obtained. We find that with the increase of the laser intensity, the photoelectron energy-angular distribution changes from circular to dumbbell shaped and is squeezed along the laser field direction. We also explore the change of the maximum photoelectron energy with laser intensity and strong-field atomic stabilization phenomenon in detail.

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“…(5). Here a uniform discrete grid point (with spacing bk) in k space, evenly distributed about k=0, will be used.…”

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Complex-scaling Fourier-grid Hamiltonian method. III. Oscillatory behavior of complex quasienergies and the stability of negative ions in very intense laser fields

Yao

Chu

1992

Phys. Rev. A

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A complex-scaling Fourier-grid Hamiltonian (CSFGH) method in momentum representation along with Floquet formalism is presented and applied to the nonperturbative treatment of the complex quasienergies of a one-dimensional-model negative chlorine ion in an ArF excimer-laser field. The CSFGH method leads to a simple and highly eScient variational procedure for accurate determination of resonance states, without the need of using an L -basis-function expansion. A variety of laser intensities are considered covering those from perturbative to very intense laser fields, and the stability of the ion is investigated under realistic experimental conditions. Oscillatory structures of the photodetachment rate as a function of field strength are found in our study, revealing that the decreasing of the detachment rate (or the so-called "stabilization" or "suppression-of-ionization" phenomenon) may not necessarily be a monotonic behavior. Physical insight into this interesting feature is explored in the Kramers-Henneberger frame, and the feasibility for the experimental observation of the oscillatory behavior of the negative ions is also discussed. PACS number(s): 32.80. Rm, 32.80.Wr, 31.15.+ q, 32.70.Jz

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Multiphoton processes in an intense laser field. V. The high-frequency regime

Cited by 122 publications

References 30 publications

Breakdown of Stabilization of Atoms Interacting with Intense, High-Frequency Laser Pulses

Breakdown of Stabilization of Atoms Interacting with Intense, High-Frequency Laser Pulses

Precision calculation of above-threshold multiphoton ionization in intense short-wavelength laser fields: The momentum-space approach and time-dependent generalized pseudospectral method

Complex-scaling Fourier-grid Hamiltonian method. III. Oscillatory behavior of complex quasienergies and the stability of negative ions in very intense laser fields

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