Search for the spectrally narrow radiative decay of 2p34So3/2in He-

Trabert, E; Heckmann, P. H.; Doerfert, J; Granzow, J

doi:10.1088/0953-4075/25/15/002

Cited by 29 publications

(21 citation statements)

References 21 publications

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“…However, to provide an example, the author chose here the He Ϫ 1s2p 2 4 P state, which is a core-excited shape resonance with a lifetime of 1 ϫ 10 Ϫ13 s, lying about 11meV above the He 1s2p 3 P 0 threshold [11][12][13]. There are at least three processes for the formation of this state: (1) laser-induced photoexcitation of the metastable 1s2s2p 4 P 0 state [12,13], (2) radiative decay of the He Ϫ 2p 3 4 S 0 excited bound state [13,14], and (3) electron scattering eϪ ϩ He 1s2p 3 P 0 (not done yet).…”

Section: Introductionmentioning

confidence: 99%

Time asymmetry, nonexponential decay, and complex eigenvalues in the theory and computation of resonance states

Nicolaides

2002

Int J of Quantum Chemistry

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Stationary-state quantum mechanics presents no difficulties in defining and computing discrete excited states because they obey the rules established in the properties of Hilbert space. However, when this idealization has to be abandoned to formulate a theory of excited states dissipating into a continuous spectrum, the problem acquires additional interest in many fields of physics. In this article, the theory of resonances in the continuous spectrum is formulated as a problem of decaying states, whose treatment can entail time-dependent as well as energy-dependent theories. The author focuses on certain formal and computational issues and discusses their application to polyelectronic atomic states. It is argued that crucial to the theory is the understanding and computation of a multiparticle localized wavepacket, ⌿ 0 , at t ϭ 0, having a real energy E 0 . Assuming this as the origin, without memory of the excitation process, the author discusses aspects of time-dependent dynamics, for t Ϸ 0 as well as for t 3 ϱ, and the possible significance of nonexponential decay in the understanding of time asymmetry. Also discussed is the origin of the complex eigenvalue Schrödinger equation (CESE) satisfied by resonance states and the state-specific methodology for its solution. The complex eigenvalue drives the decay exponentially, with a rate ⌫, to a good approximation. It is connected to E 0 via analytic continuation of the complex selfenergy function, A(z), (z is complex), into the second Riemann sheet, or, via the imposition of outgoing wave boundary conditions on the stationary state Schrödinger equation satisfied by the Fano standing wave superposition in the vicinity of E 0 . If the nondecay amplitude, G(t), is evaluated by inserting the unit operator I ϭ ͐dE|EϾϽE| G(t) ϭ Ͻ ⌿ 0 |e ϪiHt |⌿ 0 Ͼ, then the resulting spectral function is real, g(E) ϭ|Ͻ⌿ 0 |EϾ| 2 , and does not differentiate between positive and negative times. The introduction of time asymmetry, which is associated with irreversibility, is achieved by starting from Ͻ ⌿ 0 |(t)e ϪiHt |⌿ 0 Ͼ, where (t) is the step function at the discontinuity point t ϭ 0. In this case, the spectral function is complex. Within the range of validity of exponential decay, the complex spectral function is the same as the coefficient of ⌿ 0 in the theory of the CESE. A calculation of G(t) using the simple pole approximation and the constraints that t Ͼ 0 and E Ͼ 0 results in a nonexponential decay (NED) correction for t ӷ 1/⌫ that is different than when a real g(E) is used, representing the contribution of both "in" and "out" states. Earlier formal and computational work has shown that resonance states close to threshold are good candidates for NED to acquire nonnegligible magnitude. In this context, a pump-probe laser experiment in atomic physics is proposed, using as a paradigm the He Ϫ 1s2p

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Section: Introductionmentioning

confidence: 99%

Time asymmetry, nonexponential decay, and complex eigenvalues in the theory and computation of resonance states

Nicolaides

2002

Int J of Quantum Chemistry

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“…The 1s2p2p' P' shape resonance has been measured in such a way by Peterson, Coggiola, and Bae [5]. Very recently Trabert et al [16] have observed this resonance in emission from the 2p S' metastable state. The latter work was preceded by theoretical prediction of Nicolaides and Komninos [6] and Nicolaides [17], and is the first experimental confirmation of the 2p S' state as first predicted by Beck and Nicolaides [18].…”

Section: B Generalized Saddle-point Methodsmentioning

confidence: 99%

Doubly excitedPeandDo

Bylicki

1993

Phys. Rev. A

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The Feshbach projection method and the generalized saddle-point technique have been used to obtain energies of ' P' and ' D' Feshbach resonances in He, Li, and Be+. The results from both methods confirm each other. Positions and Auger energies of 31 resonances (3 in He, 14 in Li, and 14 in Be ) lying between the 2 'P' and 3 P' thresholds are given. These data can serve as a basis for identification of those resonances in future experiments. Some suggestions for such experiments are made. PACS number(s): 31.50.+w, 32.80.Dz

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“…Its energy is known from theory as being around 59.33 eV above the ground state [3,4] and, in fact, it was recently identified experimentally [5] from the predicted characteristic property of its radiative decay to the He 1s 2p P '+ e continuum [3,4].…”

Section: Known N =2 Triply Excited States Of Hementioning

confidence: 99%

“…For @McHF(1), the energy shift is small and positive whereas for @McHF (1) it is large and negative. As regards the results on the widths from expressions (5) and (6), the following facts should be noted. The final state did not include core correlation.…”

Section: Localization Interpretation Of the Mchf Solutions And mentioning

confidence: 99%

Theory and computation of triply excited resonances: Application to states ofHe−

1993

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Autoionizing multiply excited states offer unusual challenges to the theory of electronic structure and spectra because of the presence of strong electron correlations, of their occasional weak binding, of their proximity to more than one threshold, and of their degeneracy with many continua. Here we discuss a theory that addresses these difFiculties in conjunction with the computation of their wave functions and intrinsic properties. Emphasis is given on the justification of the possible presence of self-consistently obtained open-channel-like (OCL) correlating configurations in the square-integrable representation of such states and on their effect on the energy E and the width I . Application of the theory has allowed the prediction of two hitherto unknown He triply excited resonances, the 2s2p P (E=59.71 eV, above the He ground state, I =79 meV) and the 2p D' (E=59.46 eV, I =282 meV) (1 a.u. =27.2116 eV).These resonances are above the singly excited states of He and are embedded in its doubly excited spectrum. The relatively broad 2p D' state interacts strongly with the He 2s2p P' ed continuum. The effect of this interaction has been studied in terms of the coupling with fixed core scattering states as well as with a self-consistently computed OCL bound configuration. The position of the He 2p' D' resonance is below that of the He 2p 'D autoionizing state at 59.91 eV and of the He 2p P bound state at 59.68 eV. The partial decay widths to the three important open channels are y(2s2p P')=252 meV, y(1s2p 'P')=21 meV, y(1s2p 'P')=9 meV. The final core states are also represented by correlated (multiconfigurational Hartree-Fock) functions. The 2s2p P state couples to four neighboring He thresholds, the 2s2p P', 2p P, 'D, and 2s2p 'P'. It is above the He 2s2p P' threshold at 58.31 eV, with respect to which it is a valence shape resonance, and below the He 2p 'D and 2s2p 'P' autoionizing states. In the limit of an exact energy calculation, we suggest that its position would also come below that of the 2p P state, which it overlaps. Its partial widths are y(2s2p P') =60 meV, y(1s2p P') =9 meV, y(1s2p 'P') =10 meV. The present results, considered together with published ones on other n=2 intrashell states, show that the recently measured [R. N. Gosselin and P. Marmet, Phys. Rev. A 41, 1335] closely lying structures at 58.415 and 58.48 eV cannot correspond to the He 2p S' and D' states, as these authors proposed.PACS number(s): 31.50.+w, 31.20.Tz, 32.80.Dz, 34.80.Dp

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Search for the spectrally narrow radiative decay of 2p³⁴S^o_3/2in He^-

Cited by 29 publications

References 21 publications

Time asymmetry, nonexponential decay, and complex eigenvalues in the theory and computation of resonance states

Time asymmetry, nonexponential decay, and complex eigenvalues in the theory and computation of resonance states

Doubly excitedPeandDo

Theory and computation of triply excited resonances: Application to states ofHe−

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