Determination of the radiation cross sections of low-energy transitions of isomeric nuclei from observation of laser-induced γ fluorescence

Андреев, А. А.; Van’kov, A. K.; Platonov, K. Yu.; Rozhdestvenskiĭ, Yu. V.; Chizhov, S. P.; Yashin, V. E.

doi:10.1134/1.1484982

Cited by 9 publications

(8 citation statements)

References 4 publications

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“…Such studies have been undertaken for a long time [4,5] but seem to get a renewed interest with the recent advent of high-intensity laser sources [6][7][8][9]. It is now possible to create plasmas with a lifetime as long as a few nanoseconds and temperatures around several keV.…”

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confidence: 99%

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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confidence: 99%

Enhanced nuclear level decay in hot dense plasmas

Gosselin

Morel

2004

Phys. Rev. C

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“…Explicitness of this selection is partially doubted by narrow radiation (G g ¼ 1.3 Â 10 212 eV) and total decay (G T ¼ 1.6 Â 10 210 eV) widths of the 6.2 keV level (Tkalya, 2004) resulting in a rather small resonance photoabsorption cross section s g % 4.0 Â 10 213 barn. The only successful observation of the resonance fluorescence in isomeric targets (Andreev et al, 2002) was reported on 84m Rb; this is the reason why this isomer was included in Table 1. Complicated production via irradiation of bromine targets in a cyclotron and a very short half-life however cast doubt on the practical use of this isomer.…”

Section: Candidates For Excitation Of Low-lying Nuclear Levelsmentioning

confidence: 94%

“…The hitherto experiments have been performed both with stable isotopes and nuclear isomers (Irwin & Kim, 1997;Andreev et al, 2000Andreev et al, , 2002. In particular, the possibility of exciting the nuclear states in longer-living isomers via the action of the laser-produced plasma is extremely attractive.…”

Section: Introductionmentioning

confidence: 99%

Low-energy nuclear transitions in subrelativistic laser-generated plasmas

et al. 2008

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The aim of the reported research is to contribute to investigation of new processes and methods interlinking nuclear and laser-plasma physics. With respect to requirements of nuclear experiments at medium-size high-power lasers, the selection of proper candidates for studying the excitation and decay of low-lying nuclear states is reviewed. An experimental approach to the identification of low-energy nuclear transitions is discussed, simple estimates of the 181 Ta excitation yield in the laser-generated plasma provide a theoretical basis for planning future work. First tests and results of the experiments at the laser facility PALS are presented.

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“…Since the nuclear excitations have quite low cross-sections, as compared to atomic ones, high repetition rate lasers offer really new perspectives in the field of nuclear physics. Experiments have been attempted to observe the excitation of the first excited state of a few nuclei in laser generated plasma [10][11][12], however, they are not conclusive. In fact, the experimental conditions are difficult on account of the flash of particles generated during the laser shot (few fs to ns time scale), furthermore, the searched phenomena have small probabilities.…”

Section: Introductionmentioning

confidence: 98%

Energetic electrons produced in the interaction of a kiloHertz femtosecond laser with tantalum targets

Aléonard

Gobet

Claverie

et al. 2007

Journal of Modern Optics

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The electrons produced in the interaction of a high repetition rate laser with a thick tantalum target generate a continuous distribution of photons via the bremsstrahlung process occurring mainly in the target. The photon energy distributions, between 50 and 500 keV, are unfolded to obtain the true X-ray energy distributions. These distributions are used in a Monte Carlo simulation to infer the initial electron energy distributions. These properties have been studied at laser intensities ranging from 3 Â 10 15 to 6 Â 10 16 W cm À2 . The electron energy distributions are different above ' 2 Â 10 16 W cm À2 as compared to lower intensities. This is evidence for a different laser plasma interaction regime.

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Determination of the radiation cross sections of low-energy transitions of isomeric nuclei from observation of laser-induced γ fluorescence

Cited by 9 publications

References 4 publications

Enhanced nuclear level decay in hot dense plasmas

Enhanced nuclear level decay in hot dense plasmas

Low-energy nuclear transitions in subrelativistic laser-generated plasmas

Energetic electrons produced in the interaction of a kiloHertz femtosecond laser with tantalum targets

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