Reemission spectra and inelastic processes at interaction of attosecond and shorter duration electromagnetic pulses with atoms

Abstract

Abstract. Inelastic processes and the reemission of attosecond and shorter electromagnetic pulses by atoms have been considered within the analytical solution of the Schrödinger equation in the sudden perturbation approximation. A method of calculations with the exact inclusion of spatial inhomogeneity of the field of an ultrashort pulse and the momenta of photons in the reemission processes has been developed. The probabilities of inelastic processes and spectra of reemission of ultrashort electromagnetic pulses by one-and many-electron atoms have been calculated. The results have been presented in the form of analytical formulas.Progress currently achieved in the methods of generation of short and ultrashort electromagnetic pulses has allowed overcoming the "femtosecond limit" and obtaining pulses with a duration of several tens of attoseconds. As a result, attosecond physics appeared (see, e.g., reviews [1][2][3][4][5]) and it became possible to observe atomic phenomena on a real time scale. The processes accompanying the interaction of ultrashort pulses with atoms are usually described within the following approaches. For pulses shorter than the characteristic atomic time, but longer than attosecond pulses, it is appropriate to use approaches based on the Magnus expansion for the evolution operator. Only the first several terms in the expansion of the evolution operator [6] are currently used in calculations. In these calculations, the field of the pulse is assumed to be spatially uniform at the dimensions of a target [7,8]. The sudden perturbation approximation is appropriate for attosecond and shorter pulses. The possibilities of generation of pulses much shorter than attosecond ones are actively discussed (see, e.g., [9,10]). The exact solution of the Schrödinger equation in the sudden perturbation approximation for the interaction of attosecond and shorter electromagnetic pulses with multielectron atoms has been obtained in [11]. It is usually accepted [12] that the integral of the electric field strength of a laser source in vacuum with respect to time is zero. The description of the interaction of an atomic electron in the sudden perturbation approximation implies that the electron is free during the action of the field of the pulse; consequently, the absorption of laser radiation in vacuum is significantly nonlinear with respect to the field. The exact solution obtained in [11] makes it possible to calculate such effects.