Quantum-fluid-dynamics approach for strong-field processes: Application to the study of multiphoton ionization and high-order harmonic generation of He and Ne atoms in intense laser fields

Abstract

We explore the feasibility of extending the quantum-fluid dynamics ͑QFD͒ approach for quantitative investigation of nonlinear optical processes of many-electron quantum systems in intense laser fields. Through the amalgamation of the QFD and density-functional theory ͑DFT͒, a single time-dependent hydrodynamical equation of motion can be derived. This equation has the form of a generalized nonlinear Schrödinger equation ͑GNLSE͒ but includes the many-body effects through a local time-dependent exchange-correlation potential. The time-dependent generalized pseudospectral method is extended to the solution of the GNLSE in spherical coordinates, allowing nonuniform spatial discretization and efficient, accurate solution of the hydrodynamical density and wave function in space and time. The procedure is applied to the study of multiphoton ionization ͑MPI͒ and high-order harmonic generation ͑HHG͒ of He and Ne atoms in intense laser fields. Excellent agreement with other recent self-interaction-free time-dependent DFT calculations is obtained for He, while for Ne, good agreement is achieved. Four different exchange-correlation energy functionals are used in the study with an aim to explore the roles of exchange and correlation on MPI/HHG processes in details. The method offers a conceptually appealing and computationally practical approach for nonperturbative treatment of strong-field processes of many-electron systems beyond the time-dependent Hartree-Fock level.

A method for studying electron-density-based dynamics of many-electron systems in scaled cylindrical coordinates

“…It has also been observed that the algorithm is [39]. The values at the boundaries required for the solution are obtained through equation (17).…”

“…The QFD-DFT approach had been subsequently used to obtain the ground-state densities in spherical coordinates [10][11][12] as well as to study dynamical properties of two-electron systems [13][14][15][16]. There has also been an abiding interest in studying the static and dynamic properties of noble gas atoms and clusters, especially the phenomenon of above-threshold ionization (ATI), high-order harmonic generation (HHG), unusual stabilization, etc, in intense laser fields [17][18][19][20][21]. The QFD-DFT approach has been tested on such systems to study their ground-state properties by Roy and Chu [12] using a time-dependent generalized pseudospectral technique.…”

“…The QFD-DFT approach has been tested on such systems to study their ground-state properties by Roy and Chu [12] using a time-dependent generalized pseudospectral technique. They have also applied this technique to study multiphoton ionization (MPI) and HHG of He and Ne atoms in intense laser fields [17]. While such calculations in one dimension have yielded considerable insights into ultrafast processes, they might obscure some of the actual physics of these phenomena, particularly in the attosecond domain [21].…”

Information analysis in free and confined harmonic oscillator

“…By means of an optimal, non-uniform spatial grid, it leads to a symmetric eigenvalue problem, which can be easily solved by standard diagonalization routines available. It has been applied to a series of model and real systems, in both free and confined cases, viz., spiked harmonic oscillators [61,70], powerlaw and logarithmic [62], Húlthen and Yukawa [64], Hellmann [68], rational [69], exponential-screened Coulomb [71], Morse [72], hyperbolic [73], Deng-Fan [74], Manning-Rosen [75], Tietz-Hua [76], other singular [65] potentials, as well as many-electron systems within the broad domain of DFT [95,96,88,63,66,67]. Of late this has also produced excellent quality results in various radial confinement [46,47,77,78] studies in several Coulombic systems, as well as in 3DCHO.…”

Exact Quantum Solutions for Time-Dependent Charged Oscillator

“…8,9) The GPS method is capable of providing high-precision wave functions through a nonuniform spatial-grid discretization procedure. 9) As a result, Roy obtained the energy eigenvalues for systems with a wide range of coupling parameter.…”