Comment on ‘‘Multiphoton-ionization transition amplitudes and the Keldysh approximation’’

Neto, H. S. Antunes; Milonni, Peter W.

doi:10.1103/physreva.41.4095

Cited by 6 publications

(5 citation statements)

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“…If, for example, we now consider multiphoton ionization, Volkov state, which is the zeroth order of approximation of (2.9b), then we recover the Keldysh amplitude [7], whereas, if we moreover drop the gauge factor U~ of (2.3a) we obtain the Faisal-Reiss amplitude [8,9]. The usefulness of the Keldysh amplitude has been questioned by several people [41][42][43]. On the other hand, it has been successfully applied to the description of multiphoton ionization of atoms, which are modeled by a short-range potential [9,44,45].…”

Section: U~e(t) U*~(t)[v(r) + K(r T)]u~(t)ufree(t)[z(t) ) = Ih~t Iz(mentioning

confidence: 98%

A new integral equation for treating high-intensity multiphoton processes

Varró

Ehlotzky

1993

Nouv Cim D

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Summary. --In the present paper we derive a new integral equation for the non-perturbative evaluation of transition matrix elements for high-intensity multiphoton processes. Our method will be partly based on the Kramers-Henneberger transformation. In the course of the development of our theory we shall relate our approach to previous investigations along similar lines. As a specific example we shall apply our integral equation to the problem of light scattering and present a multiphoton generalization of the Kramers-Heisenberg dispersion formula. We shall then apply this general formula to the study of higher-harmonic generation from a short-range potential with a single bound state, and evaluate the rates R, of the n-th-order harmonic for a set of specifically chosen parameters. PACS 32.80.Rm -Multiphoton ionization and excitation to highly excited states (e.g., Rydberg states).

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Section: U~e(t) U*~(t)[v(r) + K(r T)]u~(t)ufree(t)[z(t) ) = Ih~t Iz(mentioning

confidence: 98%

A new integral equation for treating high-intensity multiphoton processes

Varró

Ehlotzky

1993

Nouv Cim D

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“…first learned the Keldysh theory from a preprint from ICTP Trieste by L. Davidovich et al. In fact, Davidovich later published several interesting papers on Keldysh theory [45][46][47]. In the beginning of the 1980s several non-perturbative, quantum-optics-inspired models of "continuum-continuum transitions" and ATI were introduced by Z. Białynicka-Birula [48], J.H.…”

Section: B History Of Sfamentioning

confidence: 99%

“…In fact, L. Davidovich later published several interesting papers on Keldysh theory [48][49][50]. In the beginning of the 1980s several non-perturbative, quantum-optics-inspired models of 'continuum-continuum transitions' and ATI were introduced by Białynicka-Birula [51], Eberly [52],…”

Section: History Of the Sfamentioning

confidence: 99%

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Symphony on strong field approximation

et al. 2019

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In the last three decades, we have witnessed incredible advances in laser technology and in the understanding of nonlinear laser-matter interactions, crowned recently by the award of the Nobel prize to Gérard Mourou and Donna Strickland [1,2]. It is now routinely possible to produce few-cycle femtosecond (1 fs = 10 −15 s) laser pulses in the visible and mid-infrared regimes [3,4]. By focusing such ultrashort laser pulses on gas or solid targets, possibly in a presence of nano-structures [5], the targets are subjected to an ultra-intense electric field, with peak field strengths approaching the binding field inside the atoms themselves. Such fields permit the exploration of the interaction between strong electromagnetic coherent radiation and an atomic or molecular system with unprecedented spatial and temporal resolution [6]. On one hand, HHG nowadays can be used to generate attosecond pulses in the extreme ultraviolet [7,8], or even in the soft X-ray regime [9]. Such pulses themselves may be used for dynamical spectroscopy of matter; despite carrying modest pulse energies, they exhibit excellent coherence properties [10,11]. Combined with femtosecond pulses they can also be used to extract information about the laser pulse electric field itself [12]. HHG sources therefore offer an important alternative to other sources of XUV and X-ray radiation: synchrotrons, free electron lasers, X-ray lasers, and laser plasma sources. Moreover, HHG pulses can provide information about the structure of the target atom, molecule or solid [13][14][15]. Of course, to decode such information from a highly nonlinear HHG signal is a challenge, and that is why a possibly perfect, and possibly "as analytical as possible" theoretical understanding of these processes is in high demand. Here is the first instance where SFA offers its basic services.Since electronic motion is governed by the waveform of the laser electric field, an important quantity to describe the electric field shape is the so-called absolute phase or carrier-envelope phase (CEP). Control over the CEP is paramount for extracting information about electron dynamics, and to retrieve structural information from atoms and molecules [13,16,17]. For instance, in HHG an electron is liberated from an atom or molecule through ionization, which occurs close to the maximum of the electric field. Within the oscillating field, the electron can thus accelerate along oscillating trajectories, which may result in recollision with the parent ion, roughly when the laser field approaches a zero value. Control over the CEP is particularly important for HHG, when targets are driven by laser pulses comprising only one or two optical cycles. In that situation the CEP determines the relevant electron trajectories, i.e. the CEP determines whether emission results in a single or in multiple attosecond bursts of radiation [16,18].The influence of the CEP on electron emission is also extremely important. It was demonstrated for instance in an anti-correlation experiment, in which the number of AT...

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“…The KFR-like element of our approach consists of neglecting the influence of the binding potential on the continuum electron essential states and on the electron evolution in the continuum. The physical justification and validity of such an approximation, in particular, in the context of its being a step in some systematic expansion, still remains the subject of discussions in the literature (see, e.g., Milonni and Ackerhalt 1989, Trombetta et al 1989, Antunes Neto et al 1990, Reiss 1990a, Unnikrishnan 1991, Becker et al 1994a. An intuitive argument usually used in this context is that after the electron has been transferred to the continuum, its evolution is determined mainly by the strong laser field, with the binding potential being of little importance.…”

Section: Introductionmentioning

confidence: 99%

An investigation of model above-threshold photodetachment spectra

Raczyński¹,

Zaremba²

1996

J. Phys. B: At. Mol. Opt. Phys.

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A model photodetachment is considered in a non-perturbative approach which takes into account an infinite number of virtual photon and electron states. Closed analytical formulae for the photoelectron spectrum are obtained which result from some properties of particular infinite band matrices. The formulae give account of the most characteristic features of the above-threshold detachment. A numerical example is given.

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Comment on ‘‘Multiphoton-ionization transition amplitudes and the Keldysh approximation’’

Cited by 6 publications

References 6 publications

A new integral equation for treating high-intensity multiphoton processes

A new integral equation for treating high-intensity multiphoton processes

Symphony on strong field approximation

An investigation of model above-threshold photodetachment spectra

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