Polarization bremsstrahlung in α decay

A mechanism of formation of electromagnetic radiation that accompanies α decay and is associated with the emission of photons by electrons of atomic shells due to the scattering of α particles by these atoms (polarization bremsstrahlung) is proposed. It is shown that, when the photon energy is no higher than the energy of K electrons of an atom, polarization bremsstrahlung makes a significant contribution to the bremsstrahlung in α decay.     

EC and α decays of 235Am

EC and decays of ²³⁵Am have been studied using a gas-jet coupled on-line isotope separator. Excited states in ²³⁵Pu have been established for the first time by means of -ray spectroscopy following the EC decay of ²³⁵Am. The deduced log ft value suggests that the ground state of ²³⁵Am should have the 5/2^-[523] configuration. The - coincidence result has revealed that the 5/2^-[523] state in ²³¹Np populated by the favored transition of ²³⁵Am is located at < 15 keV, which allows us to precisely determine the Q value of ²³⁵Am.     

Bremsstrahlung spectrum for α decay and quantum tunneling

Spectra of the electromagnetic radiation arising during α decay of atomic nuclei as a consequence of the motion of the α particle through a Coulomb potential barrier and in the Coulomb field of the daughter nucleus are calculated via a quantum-mechanical approach. The contributions of the E1 and E2 multipoles are calculated. Model problems of emission during motion of a charged particle through a spherically symmetric, rectangular potential barrier and a “cut-off” Coulomb barrier are treated. Numerical calculations are performed for ^210,214Po and ²²⁶Ra nuclei. Emission spectra are derived for an α particle propagating along classical trajectories in these potentials. Zh. éksp. Teor. Fiz. 116, 390–409 (August 1999)     

THE INDENPENDENT α PARTICLE MODEL OF LIGHT NUCLEI

An α particle model of light nuclei is proposed. The physical picture of the model is clear, its wave functions are simpler and convenient for some applications. When it is used in the problems of multiple scattering, each term in the series of the multiple scattering expansion can be integrated out analytically. The experiments of elastic electron scattering can be well fited by using the model wave functions. The investigations of the model indicate that the usual rigid a particle model is the classical homologue of our model.     

Improved empirical formula for α particle preformation factor

In this contribution,the α preformation factors of 606 nuclei are extracted within the framework of the generalized liquid drop model(GLDM).Through the systematic analysis of the α preformation factors of even-even Po-U isotopes,we found that there is a significant weakening of influence of N=126 shell closure in uranium,which is consistent with the results of a recent experiment [J.Khuyagbaatar et al.,Phys.Rev.Lett.115,242502(2015)],implying that N=126 may not be the magic number for U isotopes.Furthermore,we propose an improved formula with only 7 parameters to calculate α preformation factors suitable for all types of α-decay;it has fewer parameters than the original formula proposed by Zhang et al.[H.F.Zhang et al.,Phys.Rev.C 80,057301(2009)]with higher precision.The standard deviation of the α preformation factors calculated by our formula with extracted values for all 606 nuclei is 0.365 with a factor of 2.3,indicating that our improved formula can accurately reproduce the α preformation factors.Encouraged by this,the α-decay half-lives of actinide elements are predicted,which could be useful in future experiments.Notably,the predicted α-decay half-lives of two new isotopes 220 Np [Z.Y.Zhang,et al.,Phys.Rev.Lett.122,192503(2019)] and 219 Np [H.B.Yang et al.,Phys.Lett.B 777,212(2018)] are in good agreement with the experimental α-decay half-lives.     

Effects of shell correction on α decay properties

The shell correction effects on the α decay properties of heavy and superheavy nuclei have been studied in a macroscopic-microscopic manner. The macroscopic part is constructed from the generalized liquid drop model(GLDM), whereas the microscopic part, namely, the shell correction energy, brings about certain effects on the potential barriers and half-lives under a WKB approximation, which is emphasized in this work. The results show that the shell effects play a significant role in the estimation of the α decay half-lives within the actinide region.Predictions of the α decay half-lives are then generated for superheavy nuclei, which will provide useful information for future experiments.     

Darboux Transformations Between Δα=sinh α and Δα=sin α and the Application to Pseudo-Spherical Congruences in R2,1

In this Letter, it is proved that by using Darboux transformation, from a known solution of the sinh-Laplace equation (resp. sine-Laplace equation), new solutions of sine-Laplace equation (resp. sinh-Laplace equation) are obtained explicitly. The corresponding geometrical configuration is the space-like pseudo-spherical line congruence with two focal surfaces of negative constant curvature being space-like and time-like, respectively.     

Improvement of a Fission-Like Model for Nuclear α Decay

Theα decay constant is the product of the penetrability P and assault frequency vo in the fission-like model. An effective assault frequency Pv replacing the previous assault frequency uo is introduced for improvement of a fission-like model named the generalized liquid drop model （GLDM） to describe the nuclear α decay process more accurately. Two analytical formulae are proposed for the effective assault frequency due to experimental data within the GLDM. The improved model can be used to give accurate calculations for α decay half-lives.     

Nuclear Energy Density Functional and the Nuclear α Decay

We study the nuclear α decay of heavy nuclei using nuclear energy density functionals. This allows us to write the structure of the nuclear α potential inside the parent nucleus in terms of the proton and neutron density profile of the daughter nucleus with ad hoc parameters which control the strength of the potential. We adopt the Skyrme force model, Gogny force model, and relativistic mean field model to get the nucleon density profiles inside heavy nuclei. This approach is then applied to get predictions for unknown decay halflives of heavy nuclei and our results are compared with other model predictions.     

Fine structure in the α decay of202Rn

The α decay of mass-separated²⁰²Rn is studied at the ISOLDE separator. Time sequential α-singles spectra together with α-X-t and α-e-t coincidence events are collected. Fine structure in the α decay is observed and feeding of a low-lying 0 ₂ ⁺ state at 816 keV in¹⁹⁸Po is evidenced. This 0⁺ state can be interpreted as the bandhead of an intruder-state based deformed band, coexisting with the spherical groundstate band. Mixing between normal and intruder states is discussed. A preliminary α-decay study of²⁰⁰Rn did not yet reveal any fine structure.     

Particularization of α contamination using CR-39 track detectors

Solid-state nuclear track detectors (SSNTDs) have found wide use in various domains of science and technology, e.g. in environmental experiments. Measurement of α activity on sources in an environment, such as air, is not easy because of the short penetration range of the α particles. Furthermore, the measurement of α activity by most gas ionization detectors suffers from the high background induced by the accompanying gamma radiation. SSNTDs have been used successfully as detecting devices as passive system to detect the α contamination of different surfaces. This work presents the response of CR-39 (for two types) to α particles from two sources, ²³⁸Pu with energy 5 MeV and ²⁴¹Am with energy 5.4 MeV. The methods of etching and counting are investigated, along with the achievable linearity, efficiency and reproducibility. The sensitivity to low activity and energy resolution are studied.     

The α stable distribution model in ocean ambient noise

In view of the non-Gaussian ocean ambient noise,the a stable distribution is applied to the statistical modeling.Firstly,the correspondence between the model characteristic exponent and the sample kurtosis is established based on the similarity in physical meaning of the two.And the kurtosis of the sum of two independent random variables is deduced,and this can be used to explain the kurtosis characteristic of interfered background noise.Secondly,some numerical simulations are made to model samples with higher and lower kurtosis than three,the results show good adaptability in leptokurtic distribution.Finally,three typical samples are taken under quiet environment,air gun interference and ship interference environment.Their Gaussianities are judged by the quantile-quantile plot.And then the four parameters of the model are estimated by the quantile based method and characteristic function based method jointly of the three categories.The statistical law of the characteristic exponent is emphatically analyzed:in the quiet environment,the characteristic exponent is close to 2.0,which is the value of Gaussian model;but for the air gun data,it is between 1.2 and 1.7,which means leptokurtic;and under the interference of the sailing ship,the value of a is related to the ship speed and the distance from the ship source to the receiving location,the more significant the ship impact is,the smaller the characteristic exponent is,which is consistent with the variation of kurtosis of disturbing noise in physical meaning.The results of the model verification show that the a stable distribution behaves well under the above three kinds of trial conditions,especially for the air gun environment which is far superior to the normal distribution.     

Transition of β to α phase in isotactic polypropylene

In samples of isotactic polypropylene, the influence of the nucleation agent chinacridine permanent red E3B on the crystallization rate and content of α and β modifications and on the rate and mechanism of the β → α transition was investigated using x-ray diffraction, DSC microcalorimetry, and electron microscopy. It was found that, though E3B increases the content of the β phase, it is also a very efficient nucleation agent for the α-phase crystallization. The β → α transition occurring above 140°C could be characterized by a gradual melting and annealing of the β phase, accompanied by a surface crystallization of the α phase on lateral faces of β lamellae by a mechanism similar to cross-branching of α lamellae.     

Decay of 12C* into Three α Particles

Complete-kinematics data from a measurement of the decay of ¹²C^* into three α particles are analyzed. Owing to the symmetries of the three-α final state, the Dalitz plot exhibits nodes (regions of vanishing intensity) characteristic of the spin and parity of the system. Exploiting this property, we argue that a broad unidentified structure in the excitation spectrum around 12.4 MeV is likely to have unnatural spin–parity and J ≥ 4.     

Comparative studies for different proximity potentials applied to α decay

The European Physical Journal A - The energy-weighted integrated cross-section for photon absorption --known as sum rule $ \sigma_{-1}$ -- is under certain conditions proportional to the mean...     

Measurement scheme to detect α relaxation time of glass-forming liquid

A measurement scheme for detecting the α relaxation time(τ) of glass-forming liquid is proposed, which is based on the measured ionic conductivity of the liquid doped with probing ions by low-and middle-frequency dielectric spectroscopy and according to the Nernst–Einstein, Stokes–Einstein, and Maxwell equations. The obtained τ values of glycerol and propylene carbonate by the scheme are consistent with those obtained by traditional dielectric spectroscopy, which confirms its reliability and accuracy. Moreover, the τ of 1,2-propanediol in a larger temperature range is compared with existing data.     

Stochastic resonance of a tri-stable system with α stable noise

A tri-stable system excited by weak periodic signal is taken as a model and the stochastic resonance phenomenon is investigated by additive α stable noise in this paper. The laws for the resonance system parameters q, p, skewness parameter r and intensity amplification factor Q of α stable noise to act on the resonant output are explored under different stability indicies α and asymmetric skewness β of α stable noise. The results indicate that a weak signal can be realized by tuning the system parameters q, p and r under the joint action of additive α stable noise, and the interval of q and p which can induce stochastic resonance does not change with α or β. Moreover, a certain rule is found in which adjusting the intensity amplification factor Q of α stable noise can also realize a synergistic effect when studying the noise-induced stochastic resonance, and the interval of Q does not change with α or β; the best value of the characteristic index is $\alpha =1$ under any system parameter, and the best value of the symmetry parameter is $\beta =1$ under any system parameter. So, the system performance is best when $\alpha =1$ and $\beta =1$. The results will contribute to a reasonable selection of parameter-induced stochastic resonance system parameters and noise intensity of noise-induced stochastic resonance under α stable noise.