330 research outputs found
Angular analysis of bremsstrahlung in alpha decay
A new quantum electrodynamical method of calculations of bremsstrahlung
spectra in the -decay of heavy nuclei taking into account the angle
between the directions of -particle motion (or its tunneling) and
photon emission is presented. The angular bremsstrahlung spectra for
have been obtained for the first time. According to calculations,
the bremsstrahlung in the -decay of this nucleus depends extremely
weakly on the angle. Taking into account nuclear forces, such dependence is not
changed visibly. An analytical formula of the angular dependence of the
bremsstrahlung spectra is proposed and gives its harmonic behavior. The
extremal values of the angle, at which the bremsstrahlung has maximal and
minimal values, has been found.Comment: 15 pages, 1 file of figure in EPS format, LaTeX v.2e with EPJ style.
In the new variant of the paper: 1) more attention is given to a convergence
problem of computer calculations of the bremsstrahlung spectra; 2) a new
section with inclusion of Woods-Saxon component in construction of the total
realistic -nucleus potential into our model (with our first
brermsstrahlung spectra for at such potential) is included into
the paper; 3) possible ways of further improvement of the quantum-mechanical
models are pointed ou
Bremsstrahlung in Alpha-Decay
We present the first fully quantum mechanical calculation of photon radiation
accompanying charged particle decay from a barrier resonance. The soft-photon
limit agrees with the classical results, but differences appear at
next-to-leading-order. Under the conditions of alpha-decay of heavy nuclei, the
main contribution to the photon emission stems from Coulomb acceleration and
may be computed analytically. We find only a small contribution from the
tunneling wave function under the barrier.Comment: 12 pages, 2 Postscript figure
Bremsstrahlung radiation by a tunneling particle
We study the bremsstrahlung radiation of a tunneling charged particle in a
time-dependent picture. In particular, we treat the case of bremsstrahlung
during alpha-decay, which has been suggested as a promissing tool to
investigate the problem of tunneling times. We show deviations of the numerical
results from the semiclassical estimates. A standard assumption of a preformed
particle inside the well leads to sharp high-frequency lines in the
bremsstrahlung emission. These lines correspond to "quantum beats" of the
internal part of the wavefunction during tunneling arising from the
interference of the neighboring resonances in the well.Comment: 4 pages, 4 figure
Ionizing radiation exposure and the development of soft-tissue sarcomas in atomic-bomb survivors
BACKGROUND: Very high levels of ionizing radiation exposure have been associated with the development of soft-tissue sarcoma. The effects of lower levels of ionizing radiation on sarcoma development are unknown. This study addressed the role of low to moderately high levels of ionizing radiation exposure in the development of soft-tissue sarcoma. METHODS: Based on the Life Span Study cohort of Japanese atomic-bomb survivors, 80,180 individuals were prospectively assessed for the development of primary soft-tissue sarcoma. Colon dose in gray (Gy), the excess relative risk, and the excess absolute rate per Gy absorbed ionizing radiation dose were assessed. Subject demographic, age-specific, and survival parameters were evaluated. RESULTS: One hundred and four soft-tissue sarcomas were identified (mean colon dose = 0.18 Gy), associated with a 39% five-year survival rate. Mean ages at the time of the bombings and sarcoma diagnosis were 26.8 and 63.6 years, respectively. A linear dose-response model with an excess relative risk of 1.01 per Gy (95% confidence interval [CI]: 0.13 to 2.46; p = 0.019) and an excess absolute risk per Gy of 4.3 per 100,000 persons per year (95% CI: 1.1 to 8.9; p = 0.001) were noted in the development of soft-tissue sarcoma. CONCLUSIONS: This is one of the largest and longest studies (fifty-six years from the time of exposure to the time of follow-up) to assess ionizing radiation effects on the development of soft-tissue sarcoma. This is the first study to suggest that lower levels of ionizing radiation may be associated with the development of soft-tissue sarcoma, with exposure of 1 Gy doubling the risk of soft-tissue sarcoma development (linear dose-response). The five-year survival rate of patients with soft-tissue sarcoma in this population was much lower than that reported elsewhere.published_or_final_versio
Deep Hole States in Medium Mass Nuclei
Supported by the National Science Foundation and Indiana Universit
Radiation correction to astrophysical fusion reactions and the electron screening problem
We discuss the effect of electromagnetic environment on laboratory
measurements of the nuclear fusion reactions of astrophysical interest. The
radiation field is eliminated using the path integral formalism in order to
obtain the influence functional, which we evaluate in the semi-classical
approximation. We show that enhancement of the tunneling probability due to the
radiation correction is extremely small and does not resolve the longstanding
problem that the observed electron screening effect is significantly larger
than theoretical predictions.Comment: 9 pages, 1 eps figure
Multipolar model of bremsstrahlung accompanying proton-decay of nuclei
Emission of bremsstrahlung photons accompanying proton decay of nuclei is
studied. The new improved multipolar model describing such a process is
presented. The angular formalism of calculations of the matrix elements is
stated in details. The bremsstrahlung probabilities for the ,
, and nuclei decaying from
the state, the and nuclei decaying from the state, the and nuclei decaying from the
state are predicted. Such spectra have orders of values similar to the
experimental data for the bremsstrahlung photons emitted during the
-decay. This indicates on real possibility to study bremsstrahlung
photons during proton decay experimentally and perform further measurements.Comment: 14 pages, 6 figure
Quantum mechanical ab-initio simulation of the electron screening effect in metal deuteride crystals
In antecedent experiments the electron screening energies of the d+d
reactions in metallic environments have been determined to be enhanced by an
order of magnitude in comparison to the case of gaseous deuterium targets. The
analytical models describing averaged material properties have not been able to
explain the experimental results so far. Therefore, a first effort has been
undertaken to simulate the dynamics of reacting deuterons in a metallic lattice
by means of an ab-initio Hartree-Fock calculation of the total electrostatic
force between the lattice and the successively approaching deuterons via path
integration. The calculations have been performed for Li and Ta, clearly
showing a migration of electrons from host metallic to the deuterium atoms.
However, in order to avoid more of the necessary simplifications in the model
the utilization of a massive parallel supercomputer would be required.Comment: 11 pages, 12 figures, svjour class. To be published in Eur. Phys. J.
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