Intensity, pulse width, and polarization dependence of above-threshold-ionization electron spectra

Petite, G.; Agostini, Pierre; Yergeau, F.

doi:10.1364/josab.4.000765

Cited by 58 publications

(18 citation statements)

References 19 publications

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“…Several theories [2][3][4] address the tunneling ionization of atoms in an oscillatory electric field with amplitude F. Tunneling interpretations have been applied to some intense-laser multiphoton ionization (LMPI) experiments [5][6][7][8], often with noble gas atoms or their positive ions. However, given that tunneling rates increase exponentially with F and that absolute determination of relevant peak intensities & 10' W/cm in focused laser beam pulses is said [8,9] to be diNcult even to a factor of 2, LMPI experiments have not provided sensitive tests of' dynamic tunneling theory. Indeed, the term tunneling ionization was even ascribed to LMPI experiments that were analyzed with a model based on classical, over-the-barrier escape [6(a)].…”

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confidence: 99%

Dynamic tunneling ionization of excited hydrogen atoms: A precise experiment versus theories

et al. 1992

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New data for no=24, . . . , 32 H atoms ionized b' a linearly polarized, 9.908-6Hz electric field are compared with calculations.Being more precise than laser multiphoton ionization experiments with tightly bound atoms, our experiments distinguish between tunneling through and classical escape o[.er a slowly oscillating barrier and between oneand many-state dynamical processes. Formulas used to interpret low-frequency laser multiphoton ionization data poorly describe our results. Our data delineate ranges of validity of other partly successful models and are best reproduced by a new 30 semiclassical model. PACS numbers: 32.80.Rm, 03.65.Sq, 73.40.Gk While the realization that a "particle" could traverse a classically impenetrable, static potential barrier arose early in the development of quantum mechanics, there has been continuing interest in (and some controversy [I] over) quantum-mechanical tunneling. Questions being raised [I] include the definition of tunneling time(s) and how a nonstationary barrier is traversed. Several theories [2-4] address the tunneling ionization of atoms in an oscillatory electric field with amplitude F. Tunneling interpretations have been applied to some intense-laser multiphoton ionization (LMPI) experiments [5-8], often with noble gas atoms or their positive ions. However, given that tunneling rates increase exponentially with F and that absolute determination of relevant peak intensities & 10' W/cm in focused laser beam pulses is said [8,9] to be diNcult even to a factor of 2, LMPI experiments have not provided sensitive tests of' dynamic tunneling theory. Indeed, the term tunneling ionization was even ascribed to LMPI experiments that were analyzed with a model based on classical, over-the-barrier escape [6(a)].In this Letter we use tunneling to refer specifically to a transition through a barrier, where the transition connects two states having the same total energy; we also contrast this with mechanisms, such as MPI, involving transitions to states with other energies.Our dat I come from micro~ave ionization of excited H atoms. Micro~ave technology facilitates precise determinations [10] of the field amplitude and pulse shape, a major advantage over LMPI experiments. Moreover, the simplicity of the hydrogen atom allows us to model details of the ionization process and make a direct comparison between experiment and theories. We find that a theory [4] often used [6-8] to model laser tunneling ion-Ization experiments fails to describe the present data. lt is convenient to use classically scaled variables [11] (r)t, .FO) for the f'requency to and amplitude F (atomic units are used throughout) of the applied field, where t&o=njj'to and Fo=noF The classical dyn. amics [11,12] depends on only these and not separately on m, F, and the principal classical action 10, here set equal (in a.u. ) to no Using results from Ref. [13] for each parabolic substate n =(no, n~,~m~), the highest [lowest] critical field F, '. ("(n) for classical escape is F0=0.38 [Fo=0.13] for the extremal upward-g...

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Dynamic tunneling ionization of excited hydrogen atoms: A precise experiment versus theories

et al. 1992

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“…II ionization of a low-lying Rydberg state by an elliptically polarized microwave field, such one as of the form given in Eq. (5), should provide interesting and counterintuitive results. We begin by considering the case of equal amplitudes in both fields and /=90, in circular polarization.…”

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confidence: 99%

“…On the other hand, the energy resides in the oscillation of the electron, and it is converted to translational energy when the electron leaves the laser focus, so the ponderomotive energy shift is not apparent in electrons detected outside the focus [4]. Although we do not consider the case here, it is interesting to note that with short-pulse lasers the electrons do not leave the laser focus during the pulse and thus do not regain the ponderomotive energy [5]. Third, the angular distribution of the ejected electrons is strongly influenced by the ponderomotive eFects [6].…”

Section: Introductionmentioning

confidence: 99%

Angular distribution of electrons from low-frequency above-threshold ionization

Baruch

Gallagher

1991

Phys. Rev. A

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We have measured the angular distribution of electrons produced by microwave ionization of Na in a 9.4-GHz field. Microwave fields of up to 10.5 kV/cm with linear, circular, and elliptical polarizations were generated in a rotatable Fabry-Perot cavity. The electron angular distributions obtained are consistent with the predictions of a classical theory of above-threshold ionization in the low-frequency limit.PACS number(s): 32.80.Rm

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“…If the electron does not move far enough to experience the gradient in the irradiance, the pondermotive energy returns to the laser beam by stimulated scattering. Thus for short laser pulses the detected electron energy and trajectory are the actual electron energy and trajectory at the time of ionization [90,91].…”

Section: Wavelength Comparisonmentioning

confidence: 99%

Optical field ionization of atoms and ions using ultrashort laser pulses

Fittinghoff¹

1993

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Intensity, pulse width, and polarization dependence of above-threshold-ionization electron spectra

Cited by 58 publications

References 19 publications

Dynamic tunneling ionization of excited hydrogen atoms: A precise experiment versus theories

Dynamic tunneling ionization of excited hydrogen atoms: A precise experiment versus theories

Angular distribution of electrons from low-frequency above-threshold ionization

Optical field ionization of atoms and ions using ultrashort laser pulses

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