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arXiv:nucl-th/0405043 · Physical Review C

Hidden evidence of nonexponential nuclear decay

N. G. Kelkar, Marek Nowakowski, Kanchan Khemchandani

Published Aug 17, 2004• 43 citations
arXivHTMLPDF

Abstract

The framework to describe natural phenomena at their basics being quantum mechanics, there exist a large number of common global phenomena occurring in different branches of natural sciences. One such global phenomenon is spontaneous quantum decay. However, its long time behavior is experimentally poorly known. Here we show, that by combining two genuine quantum mechanical results, it is possible to infer on this large time behavior, directly from data. Specifically, we find evidence for nonexponential behavior of alpha decay of $^{8}\mathrm{Be}$ at large times from experiments.

DOI
10.1103/physrevc.70.024601

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The framework to describe natural phenomena at their basics being quantum mechanics, there exist a large number of common global phenomena occurring in different branches of natural sciences. One such global phenomenon is spontaneous quantum decay. However, its long time behavior is experimentally poorly known. Here we show, that by combining two genuine quantum mechanical results, it is possible to infer on this large time behavior, directly from data. Specifically, we find evidence for nonexponential behavior of alpha decay of 8Be^{8}\mathrm{Be}8Be at large times from experiments.
The most important law of radioactivity is that of the exponential decay. In the realm of quantum mechanics, however, this decay law is neither rigorous nor fundamental. The deviations from the exponential decay have been observed experimentally at the early stage of a decay process, but there is little evidence for nonexponential behavior at long times. Yet such long-term nonexponentiality is expected theoretically to probe the nonresonant background components of the initial wave function which preserve the structural interference and the memory of how the state was created. In this paper, we propose new observables that can be used for experimental investigations of the post-exponential decay regime, including the decay of threshold resonances, particle correlations in three-body decays, and interference between near-lying resonances. While the specific examples presented in this work pertain to atomic nuclei, the properties of nonexponential decay are generic, i.e., they apply to other many-body open quantum systems, such as hadrons, atoms, molecules, and nanostructures.
Precision tests of decay law of radioactive nuclei have not so far found any deviation from the exponential decay law at early time, as predicted by quantum mechanics. In this paper, we show that the quantum decoherence time (i.e. the timescale of nonexponential decay) of the quasifission or fission process should be of the order of attosecond considering the atom of the fissioning nucleus as a quantum detector. Hence, the observed decay timescale of the quasifission or fission process of even highly excited (EX greater than 50 MeV) transuranium and uraniumlike complexes should be rather long (of the order of attosecond) in spite of their very fast exponential decay timescale (of the order of zeptosecond) as measured by the nuclear techniques. Recent controversy regarding the observation of very long (of the order of attosecond ) and very short (of the order of zeptosecond ) quasifission or fission timescales for similar systems at similar excitation energies as obtained by direct techniques (crystal blocking, X ray fission fragment) and nuclear techniques could be interpreted as evidence for nonexponential decays in nuclear systems
The self-consistent methods in time analysis of nuclear collisions and decays are based on the properties of time as a quantum observable, canonically conjugate to energy, and the appropriate definition of mean durations of quantum collisions, the variances in their distributions, the decay functions, and the surviving functions of the meta-stable states, including radioactive and compound nuclei. Even a simplified application of these methods for the elementary study of the α-decay in the exponential-law-decay approximation resulted in the simple phenomenological method of the determination of the α-particle one-step virtual and real sojourn time inside the parent α-radioactive nucleus between the α-particle successive incoherent multiple internal reflections during the α-decay. And also the direct temporal study of the quasi-monochromatic proton scattering by 12 C and 14 N nuclei at the range of isolated resonances distorted by the nonresonant background, accompanied by the bremsstrahlung, brings to the simple revealing of the possible existence of the delay–advance phenomenon in the proton emission during scattering (in the center-of-mass system). The utilization of the self-consistent methods of time analysis to the study of high-energy nuclear reactions (near and above 0.1 GeV per nucleon in the final compound–fragment formations) resulted in the discovery of the phenomenon of time resonances (or explosions) for such formations. Some perspectives of the further study of the evident temporal phenomena in nuclear processes are also indicated.
This project presents a conceptual and mathematical hypothesis concerning the apparent randomness of radioactive decay. While current nuclear physics models describe decay as a fundamentally stochastic and random process with a constant decay rate, this work explores the possibility that the randomness may come from rapidly fluctuating internal nuclear states that are not directly obsercable by measurement. The central idea is that the effective decay constant measured experimentally represents a time-averaged quantity over a distribution of internal configurations, associated with slightly different decay probabilities. In this framework, radioactive decay remains statistically exponential at observable timescales, while allowing for hidden internal dynamics consistent with established quantum mechanical principles. My work does not claim experimental verification. Instead, it aims to outline a phenomenological structure compatible with known decay laws and to identify conditions under which small, systematic deviations might arise under perturbations.
Abstract Several experimental groups reported the evidence of periodic modulations of nuclear decay constants which amplitudes are of the order 10−3{{10}^{{ - 3}}}10−3 and periods of one year, 24 h or about one month. We argue that such deviations from radioactive decay law can be described in nonlinear quantum mechanics framework, in which decay process obeys to nonlinear Shrödinger equation with Doebner–Goldin terms. Possible corrections to Hamiltonian of quantum system interaction with gravitation field considered, it’s shown that they correspond to some emergent gravity theories, in particular, bilocal field model. It’s shown that proposed model describes decay parameter variations which agree with experimental results for Po-214 α\alpha α -decay life-time oscillations.
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