Enhanced Electron-Capture Decay Rate of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mmultiscripts><mml:mi mathvariant="normal">B</mml:mi><mml:mprescripts /><mml:none /><mml:mn mathvariant="normal">7</mml:mn></mml:mmultiscripts><mml:mi mathvariant="normal">e</mml:mi></mml:math>Encapsulated in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi mathvariant="normal">C</mml:mi><mml:mn mathvariant="normal">60</mml:mn></mml:msub></mml:math>

Ohtsuki, T.; Yuki, Heimei; Muto, M.; Kasagi, J.; Ohno, Kaoru

doi:10.1103/physrevlett.93.112501

Cited by 91 publications

(55 citation statements)

References 31 publications

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“…Apart from variations of the electroweak coupling constants in the high energy range (cf. [2], chapter 27; [3], chapter 17), even in the low energy range changes of the decay rates are possible [1,4].…”

Section: Introductionmentioning

confidence: 99%

Change of Electroweak Nuclear Reaction Rates by CP- and Isospin Symmetry Breaking – A Model Calculation

Stumpf

2006

Zeitschrift Für Naturforschung A

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Based on the assumption that electroweak bosons, leptons and quarks possess a substructure of elementary fermionic constituents, in previous papers the effect of CP-symmetry breaking on the effective dynamics of these particles was calculated. Motivated by the phenomenological procedure in this paper, isospin symmetry breaking will be added and the physical consequences of these calculations will be discussed. The dynamical law of the fermionic constituents is given by a relativistically invariant nonlinear spinor field equation with local interaction, canonical quantization, selfregularization and probability interpretation. The corresponding effective dynamics is derived by algebraic weak mapping theorems. In contrast to the commonly applied modifications of the quark mass matrices, CP-symmetry breaking is introduced into this algebraic formalism by an inequivalent vacuum with respect to the CP-invariant case, represented by a modified spinor field propagator. This leads to an extension of the standard model as effective theory which contains besides the "electric" electroweak bosons additional "magnetic" electroweak bosons and corresponding interactions. If furthermore the isospin invariance of the propagator is broken too, it will be demonstrated in detail that in combination with CP-symmetry breaking this induces a considerable modification of electroweak nuclear reaction rates.

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Section: Introductionmentioning

confidence: 99%

Change of Electroweak Nuclear Reaction Rates by CP- and Isospin Symmetry Breaking – A Model Calculation

Stumpf

2006

Zeitschrift Für Naturforschung A

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“…(It should be noted that we have also measured the half-life of 7 Be in a sample of 7 Be@C60. The results have been presented in another paper 15,16) ). Finally, we obtained the half-life (T 1=2 ) for the sample of Be metal crystal ( 7 Be), which is 53:25 AE 0:04 days.…”

Section: Resultsmentioning

confidence: 82%

Lifetime Measurement of <SUP>7</SUP>Be in Beryllium Metal Crystal

Ohtsuki

Ohno

Morisato³

et al. 2007

Mater. Trans.

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The decay rate of an electron-capture nucleus is proportional to the electron density in the nucleus. In order to see how the decay rate can be changed artificially, we have measured the half-life of 7 Be in a beryllium (Be) metal crystal. We found that it is 53:25 AE 0:04 days, which is slightly longer than that in hosts such as graphite, lithium fluoride, and others that have previously been tested.

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“…Less dramatic is the recently discovered 1% shortening of the ground-state half-life of 7 Be when the atoms are caged within C 60 buckeyballs. 17 The sensitivity of nuclear decay to the atomic environment gives hope that mixed atomic-nuclear effects may eventually provide a way to induce energy release from isomers.…”

Section: Inducing Premature Decaymentioning

confidence: 99%

Ups and Downs of Nuclear Isomers

Walker¹,

Carroll²

2005

Physics Today

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W hat could one do with a clean source of nuclear energy? That tantalizing question reflects a dream that some have hoped to realize by exploiting the energy-storage capabilities of nuclear isomers. But the hope hinges on facets of nuclear behavior that remain unknown despite decades of study. Electromagnetic transitions and b decay, the basic mechanisms that largely determine isomer halflives, are well understood. In many cases, however, it is still not possible to predict half-lives even to within an order of magnitude.Today's isomer research seeks a better understanding of the degrees of freedom that will reveal new aspects of nuclear structure and lead the way to new applications. In this article, we lay out the essential ingredients of nuclear isomerism and take a look at future possibilities. Metastable excited statesThe term "isomer" is borrowed from chemistry, where it refers to molecules that have different geometrical configurations of the same collection of atoms. Isomeric nuclei, as distinguished from isotopes, are different states of the same numbers of protons and neutrons. Whereas chemical isomers have energy states that are similar, sometimes identical, to each other, nuclear isomers always have different energies. Excitation energies can be as high as several MeV.An interesting example of a nuclear isomer is 99m Tc, an excited state of technetium-99. The "m" after the mass number denotes a metastable state-that is, a long-lived isomer. The half-life of 99m Tc is six hours and its excitation energy above the nuclear ground state of 99 Tc is 143 keV. By contrast, typical half-lives of excited nuclear states are about a picosecond. Isomers live at least a thousand times longer. The appellation is usually reserved for excited nuclear states that live longer than a nanosecond. The superscript "m" is even more restrictive; it's reserved for isomers with half-lives of more than a millisecond. If a nuclear species has more than one metastable isomer, an ordinal number after the "m" distinguishes between them in ascending order of excitation energy.Perhaps the most widely known nuclear isomer is the long-lived hafnium excitation 178m2 Hf. With a half-life of 31 years, it sits 2.4 MeV above the stable 178 Hf ground state. The exceptional combination of high excitation energy and conveniently long halflife has led to claims for practical applications that have lent the hafnium isomer unusual visibility (see PHYSICS TODAY, May 2004, page 21).Nature's sole example of an isomer long-lived enough to be called stable is 180m Ta. This tantalum isomer's half-life exceeds 10 15 years. One can only quote a lower lifetime limit, because the isomer's spontaneous decay has never been observed. But the isomer sits 77 keV above a ground state that is itself unstable, with a b-decay halflife of only eight hours.Isomers can lose their excess energy by the usual radioactive decay modes: a, b, or g. The favored mode in any particular case depends on the energies and quantum numbers of the states involved. Decay by neutron o...

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Enhanced Electron-Capture Decay Rate ofB7eEncapsulated inC60

Cited by 91 publications

References 31 publications

Change of Electroweak Nuclear Reaction Rates by CP- and Isospin Symmetry Breaking – A Model Calculation

Change of Electroweak Nuclear Reaction Rates by CP- and Isospin Symmetry Breaking – A Model Calculation

Lifetime Measurement of <SUP>7</SUP>Be in Beryllium Metal Crystal

Ups and Downs of Nuclear Isomers

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