Two-frequency multiphoton ionization of hydrogen atoms

Leone, Cláudio; Bivona, S.; Burlon, R.; Ferrante, G.

doi:10.1103/physreva.38.5642

Cited by 46 publications

(20 citation statements)

References 14 publications

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“…As discussed in ref. [9], ansatz (10) is a satisfactory approximation to the exact solution when energetic photoelectrons are concerned, the discrete part of the atomic spectrum does not play any role and relatively intense laser fields are considered.…”

Section: (R T) = Lim Exp [-Iet/h] ~E (R Tl T2) Tl---) T Ts---~tmentioning

confidence: 99%

“…[9] and specialized to the case when one of the fields was of low intensity and relatively high frequency, and the other was of low frequency and high intensity. The model was based on the following physical picture: the bound electron, after absorbing simultaneously one photon of high frequency and exchanging n photons of low frequency, decays into a continuum through a singlestep process, regardless of the nature of the atomic spectrum; in the final state, the electron moves under the action of the potential field of the residual ion and the radiation field of high intensity.…”

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confidence: 99%

“…Multiphoton ionization and detachment by two radiation fields have been recently studied both experimentally [i-7] and theoretically [8][9][10][11][12][13][14]. In particular, the experimental work on the multiphoton ionization process reported in ref.…”

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confidence: 99%

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Simultaneous multiphoton ionization by two radiation fields. Effects of the statistical properties of the radiation

1991

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Summary.--We report on calculations of differential and total ionization crosssections of hydrogen atoms irradiated by two radiation fields with different properties. One of the fields is of low intensity and relatively high frequency, the other is of low frequency and high intensity. In particular, we show that the inclusion of the multimode structure of the low-frequency laser field modifies considerably the shape of the angular distribution of the photoelectrons and the rates of ionization into the different channels characterized by the number of low-frequency photons exchanged. Further, we find that the average energy exchanged between the photoelectrons and the low-frequency radiation field is independent of the statistical properties of the low-frequency laser field.PACS 32.80 -Photon interactions with atoms.

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Section: (R T) = Lim Exp [-Iet/h] ~E (R Tl T2) Tl---) T Ts---~tmentioning

confidence: 99%

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confidence: 99%

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Simultaneous multiphoton ionization by two radiation fields. Effects of the statistical properties of the radiation

1991

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“…(3) (q, I g(a))=&e ' IF~rliip(r)) (4) FI q sino, FLcosu Aq =, ICL(a) = COL COL (5) q=qp+qT is the average momentum of the ejected electron moving under the action of the LF field, qz is its component along the direction of the fields, and FH and HF field amplitude. To arrive at Eq.…”

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confidence: 99%

“…[2,5,6]). Therefore, here we quote the basic formulas giving the transition rate of the process in which the electron is detached in a single step after absorbing one HF photon and exchanging n LF photons (hereafter atomic units will be used):…”

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Electron energy distribution in the photodetachment ofH−by two radiation fields

1993

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We report on the energy distribution of the electrons emitted in two-color photodetachment of H in a highly nonlinear regime, and compare these results with the ones found by averaging the cross section obtained in the presence of a static field over the values taken by the low-frequency field in a cycle. Similarities and differences are discussed. PACS number{s): 32.80.RmOver the last few years, multiphoton detachment of negative ions has become a topic of both theoretical and experimenta. investigation. The main reason for carryi'ng out experiments with these systems arises from the short-range nature of the interaction between the atomic core and the outer electron that allows a clearer determination of the continuum threshold as compared to the one measured in analogous experiments where use is made of neutral atoms. This circumstance has stimulated experiments aimed at measuring the detachment threshold shift due to the presence of a strong radiation field. For this purpose experiments of detachment of negative chlorine ions by a weak field of frequency coH in the presence of a strong microwave or infrared field of frequency co'I have been carried out [1]. In these experiments the role of the intense low-frequency field (LF) of amplitude I'L was to provide the ponderomotive shift b =FL l4mcol (with m the electron mass), while the intensity of the higher-frequency field (HF) was so weak that only one HF photon was absorbed in the photodetachment process. Experimental results were obtained in two different physical regimes characterized by the ratio 6/coL, for co~in the region of uv frequencies and col in the range of infrared or microwave frequencies. In the regime characterized by 6/cuL ))1 it was not possible to make any connection between the threshold shift and the measured cross section [1,2]. The ripples found in the curve showing the cross section as a function of AH were interpreted [1 -3] in terms of interference of the direct photoelectron wave and the wave that rejects from the repulsive barrier formed by the LF field whose characteristic height was evaluated [3] to be 2b" in analogy with the explanation given in Ref. [4], where the photodetachment in the presence of a static electric field was studied. Moreover, the poor sensitivity of the photodetachment event to the variation of coL was considered as a manifestation of the quasistaticity of the process. The cross sections were in fact proved to have a behavior quite similar to the ones obtained by averaging the cross sections of photodetachment in a static electric field over the values taken by the LF field in a period [2]. The present paper is aimed at further comparing the photodetachment process of H occurring in the presence of a static field with the one in an oscillating intense field, taking the latter as linearly polarized along the direction of the HF field and where T"(q,XI )= f da f"(a)M(q, KI (a)), (2) f"(a) = exp in a+i A+i sin, a 2~L (3) (q, I g(a))=&e ' IF~rliip(r)) (4) FI q sino, FLcosu Aq =, ICL(a) = COL COL (5)q=qp+qT is the a...

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Influence of a plasma medium on laser assisted radiative recombination

et al. 2004

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The problem of laser assisted radiation recombination, taking into account the influence of the plasma in which the elementary process takes place, is investigated theoretically. Among the reported results, remarkable broadening and enhancement of the X-ray photon emission spectrum is found, provided some conditions are met. First, a sufficiently intense laser field must assist the process. For enhancement, the intensity must be such that the amplitude of the quiver electron velocity be comparable or slightly larger than the electron thermal velocity. For broadening it is important that at the level of the elementary act of recombination several multiphoton channels be open. A judicious compromise between the plasma temperature and the field intensity is necessary to have many effective slow electrons able to absorb large numbers of photons from the assisting laser field to be converted into X-ray photons. Emitted power spectra per steradian and frequency unit of the emitted photon J(ω x ) in a.u. as a function ω x for a Maxwellian EDF, ion charge Z=3, ω L =0.057 a.u., laser intensity I L = 6×10 15 W/cm 2 , different values of plasma temperature: dotted line T =1a.u. and R=7.3; thick line T=1,5 a.u. and R=5.9; thin line T= 2 a.u. and R=5.1

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Two-frequency multiphoton ionization of hydrogen atoms

Cited by 46 publications

References 14 publications

Simultaneous multiphoton ionization by two radiation fields. Effects of the statistical properties of the radiation

Simultaneous multiphoton ionization by two radiation fields. Effects of the statistical properties of the radiation

Electron energy distribution in the photodetachment ofH−by two radiation fields

Influence of a plasma medium on laser assisted radiative recombination

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