Temporary anions - calculation of energy and lifetime by absorbing potentials: the resonance

Sommerfeld, Thomas; Riss, Uwe V.; Meyer, Hans‐Dieter; Cederbaum, Lorenz S.; Engels, Bernd; Suter, H. U.

doi:10.1088/0953-4075/31/18/009

Cited by 123 publications

(136 citation statements)

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“…, 9, and for the laserphoton basis, we included the simultaneous emission and absorption of up to 20 photons. The non-Hermitian Hamiltonian matrix (dimension 41000) was diagonalized using a Lanczos algorithm for complex-symmetric matrices [14]. All results are converged with respect to the electronic and photonic basis sets and the number of Lanczos iterations.…”

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confidence: 99%

Electromagnetically Induced Transparency for X Rays

2007

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Electromagnetically induced transparency (EIT) is predicted for x rays in laser-dressed neon gas. The x-ray photoabsorption cross section and polarizability near the Ne K edge are calculated using an ab initio theory suitable for optical strong-field problems. The laser wavelength is tuned close to the transition between 1s −1 3s and 1s −1 3p (∼ 800 nm). The minimum laser intensity required to observe EIT is of the order of 10 12 W/cm 2 . The ab initio results are discussed in terms of an exactly solvable three-level model. This work opens new opportunities for research with ultrafast x-ray sources.PACS numbers: 32.30. Rj, 32.80.Fb, 32.80.Rm, 42.50.Hz In a Λ-type medium characterized by atomic levels a, b, and c with energies E a > E b > E c , resonant absorption on the c → a transition can be strongly suppressed by simultaneously irradiating the medium with an intense laser that couples the levels a and b. This phenomenon is known as electromagnetically induced transparency (EIT) [1,2,3]. EIT enables one to control the absorption and dispersion of a gaseous medium. It has become a versatile tool for creating media with exceptional optical properties [4,5,6,7]. EIT forms the basis of a recent proposal for a high-accuracy optical clock [8].In this Letter, we study EIT for x rays. Specifically, we consider the near-K-edge structure of neon gas in the presence of a linearly polarized 800-nm laser with an intensity of 10 13 W/cm 2 . The decay widths of excited states involved in EIT in the optical regime typically do not exceed ∼ 10 −4 eV (see, e.g., Ref.[2]) and are often much smaller. In contrast, the decay width of core-excited neon, Γ 1s = 0.27 eV [9], is larger by a factor of ∼ 2000. Therefore, as we will show below, the intensity of the coupling laser must be extraordinarily high. This represents the first case of EIT where the laser causes strong-field ionization of the two upper levels.Because of their high binding energy, the core and valence electrons of Ne remain essentially unperturbed at 10 13 W/cm 2 . (Multiphoton ionization of Ne in its ground state is negligible.) However, laser dressing of the core-excited states introduces strong-field physics: For the laser parameters employed here, the ponderomotive potential [10] is U p = 0.60 eV, and the energy needed to ionize, for instance, the 3p electron in the 1s −1 3p state is I 1s −1 3p = 2.85 eV (1s −1 3p denotes the state produced by exciting a 1s electron to the 3p Rydberg orbital). Hence, the Keldysh parameter [11] is γ = I 1s −1 3p /(2 U p ) = 1.5. For γ ≪ 1, the atom-field interaction can be described in the adiabatic tunneling picture; the perturbative multiphoton regime is indicated by γ ≫ 1. In our case, where γ ≈ 1, the nonadiabatic strong-field regime persists; neither perturbation theory nor a tunneling description is adequate. It should also be noted that the transition energy between, e.g., the states 1s −1 3s and 1s −1 3p is 1.69 eV, which is, within the decay width of the core-excited states, in one-photon resonance with the 1.55-eV la...

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confidence: 99%

Electromagnetically Induced Transparency for X Rays

2007

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“…Santra and Cederbaum [7] not only showed that such a process is energetically possible but also proved that it is very efficient. Utilizing the CAP-CI (configuration interaction with complex absorbing potential) technique [11] they calculated a decay lifetime of about 80 fs for the one-site inner-valence excited states of the (Ne 2 ) 2+ dication. As in the case of singly ionized clusters other related processes such as ETMD can occur as well.…”

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confidence: 99%

Ab initio calculation of interatomic decay rates of excited doubly ionized states in clusters

Kolorenč

Averbukh

Gokhberg

et al. 2008

The Journal of Chemical Physics

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Recently, a computational technique for ab initio calculation of the inter-atomic and intermolecular non-radiative decay processes has been developed [1]. It combines the Fano formalism with the Green's function method known as the algebraic diagrammatic construction. The problem of normalization of continuum wave functions stemming from the use of the Gaussian basis sets is solved by using the Stieltjes imaging technique. In the present paper, the methodology is extended in order to describe the inter-atomic decay of excited doubly ionized states of clusters. The new computational scheme is applied to compute the inter-atomic decay rates of doubly ionized states formed by Auger relaxation of core vacancies in NeAr and MgNe van der Waals clusters.

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“…Recent years have witnessed advances in ab initio quantum chemical techniques using the analytical continuation methods for probing the electronic resonances in atoms and molecules [1][2][3][4][5][6][7][8][9][10]. The advantage of analytical continuation of the Hamiltonian in the complex plane giving the direct access to the resonances parameters is that they can be represented by using L 2 wavefunction [1].…”

Section: Introductionmentioning

confidence: 99%

“…The electron correlation and relaxation effects are clearly crucial factors in the formation and decay of the metastable states [6,15]. The accuracy of the effective oneparticle based approximations in the case of an electron scattering resonance depends on the extent to which the electron correlation is important in the description of particular states.…”

Section: Introductionmentioning

confidence: 99%

“…The accuracy of the effective oneparticle based approximations in the case of an electron scattering resonance depends on the extent to which the electron correlation is important in the description of particular states. CAP potentials have been applied to the molecular resonances in the context of configuration interaction [CI] [6] and electron propagator theories [3,4] and coupled-cluster based methods [7][8][9]. In these calculations, the resonance energies and width are calculated from the difference between the ground state total energies of the [N ± 1] and the neutral target.…”

Section: Introductionmentioning

confidence: 99%

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