First-principles calculation of the cross sections for nuclear excitation by electron capture of channeled nuclei

Yuan, Zhu-Shu; Kimball, J. C.

doi:10.1103/physrevc.47.323

Cited by 21 publications

(16 citation statements)

References 19 publications

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“…Simplified theoretical models [13][14][15] have been developed around those experiments, but they may not be extrapolated to plasmas. A more sophisticated theoretical model [16], while it may more easily be extrapolated to plasmas, shows several orders of magnitude discrepancies with the other models. In any case, definitive experimental evidence of NEEC existence remains to be observed.…”

Section: Nuclear Excitation By Electron Capture and Internal Convementioning

confidence: 91%

Enhanced nuclear level decay in hot dense plasmas

Gosselin

Morel

2004

Phys. Rev. C

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A model of nuclear level decay in a plasma environment is described. Nuclear excitation and decay by photon processes, nuclear excitation by electron capture, and decay by internal conversion are taken into account. The electrons in the plasma are described by a relativistic average atom model for the bound electrons and by a relativistic Thomas-Fermi-Dirac model for the free electrons. Nuclear decay of isomeric level may be enhanced through an intermediate level lying above the isomer. An enhanced nuclear decay rate may occur for temperatures far below the excitation energy of the transition to the intermediate level. In most cases, the enhancement factor may reach several decades. PACS number(s): 23.20.NxIn a hot dense plasma, either laser heated or of astrophysical interest [1-3], nuclei in an isomeric state may have a decay rate different from the laboratory value. The large number of photons and free electrons modifies the environment in which the nucleus naturally decays under laboratory conditions through spontaneous emission and internal conversion (IC). In the plasma, the IC decay rate can be modified by the lower number of available electrons in the partially ionized atom. Moreover, new decay modes also appear such as induced photon emission, free electron scattering, or bound internal conversion.Furthermore, indirect decay channels may be opened, if there exists a nuclear level lying above the isomeric level that may be excited from the isomeric state, and then decay down to the ground state. At first glance, one may expect that this indirect decay mode may become significant when the temperature is around the energy difference between the isomeric level and the upper level. However, if the multipolarities of the excitation transition of the intermediate level and of its decay are more favorable than that of the isomeric transition, one may expect that the indirect decay mode becomes predominant at a lower temperature.This indirect process would be a valuable tool for investigating nuclear excitation in plasmas. In a laser heated plasma, it could provide experimental conditions allowing tests of the nuclear transition rate model as well as the ability to reach significantly populated higher energy nuclear levels. These studies are critical for nuclear energy storage on an isomeric level and its release mechanism.If these hot plasmas are maintained for a long enough duration at the thermodynamic equilibrium at a temperature T, the different nuclear level populations reach an equilibrium given by the Boltzmann law where the ratio between any two populations N i and N f is easily calculated:where k B is the Boltzmann constant, E i and E f the excitation energies, and J i and J f the spins of lower initial state i and the upper final state f.One remarkable feature of the thermodynamic equilibrium is that the populations can be calculated without any explicit knowledge of the detailed excitation and decay processes. However, in the case of plasmas where only the nuclear populations are not at equilibrium, i...

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Section: Nuclear Excitation By Electron Capture and Internal Convementioning

confidence: 91%

Enhanced nuclear level decay in hot dense plasmas

Gosselin

Morel

2004

Phys. Rev. C

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“…Several theoretical studies have been made concerning NEEC in plasmas [23,29] or in solid targets [30,31,32].…”

Section: Introductionmentioning

confidence: 99%

Nuclear-resonant electron scattering

Pálffy

Harman

2008

Phys. Rev. A

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We investigate nuclear-resonant electron scattering as occurring in the two-step process of nuclear excitation by electron capture (NEEC) followed by internal conversion. The nuclear excitation and decay are treated by a phenomenological collective model in which nuclear states and transition probabilities are described by experimental parameters. We present capture rates and resonant strengths for a number of heavy ion collision systems considering various scenarios for the resonant electron scattering process. The results show that for certain cases resonant electron scattering can have significantly larger resonance strengths than NEEC followed by the radiative decay of the nucleus. We discuss the impact of our findings on the possible experimental observation of NEEC.

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“…Several theoretical studies have been made concerning NEEC in plasmas [7,10] or in solid targets [11,12,13]. In [14] we presented relativistically correct theoretical cross sections for NEEC followed by the radiative decay of the nuclear excited states for highly charged heavy ions.…”

Section: Introductionmentioning

confidence: 99%

Quantum interference between nuclear excitation by electron capture and radiative recombination

2007

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We investigate the quantum interference between the resonant process of nuclear excitation by electron capture ͑NEEC͒ followed by the radiative decay of the excited nucleus, and radiative recombination ͑RR͒. In order to derive the interference cross section, a Feshbach projection operator formalism is used. The electromagnetic field is considered by means of multipole fields. The nucleus is described by a phenomenological collective model and by making use of experimental data. The Fano profile parameters as well as the interference cross section for electric and magnetic multipole transitions in various heavy ions are presented. We discuss the experimental possibility of discerning NEEC from the RR background.In this section we derive the total cross section of the recombination process involving NEEC followed by the radiative decay of the nucleus and RR by means of a Feshbach projection operator formalism. We consider that the electron is captured into the bound state of a bare ion or an ion with a closed-shell configuration. We calculate the interference term between NEEC followed by the radiative decay of the excited nucleus and RR in the total cross section for electric and magnetic multipole transitions of the nucleus. A. The interference between RR and NEEC in the total cross sectionThe initial state ͉⌿ i ͘ of the system describing the nucleus in its ground state, the free electron, and the vacuum state of *Electronic address:Adriana-Claudia.Gagyi-Palffy@unigiessen.de † Electronic address: Harman@mpi-hd.mpg.de PHYSICAL REVIEW A 75, 012709 ͑2007͒

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First-principles calculation of the cross sections for nuclear excitation by electron capture of channeled nuclei

Cited by 21 publications

References 19 publications

Enhanced nuclear level decay in hot dense plasmas

Enhanced nuclear level decay in hot dense plasmas

Nuclear-resonant electron scattering

Quantum interference between nuclear excitation by electron capture and radiative recombination

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