Alpha-particle Decay Research Articles

Critical Examination of Gamow's Theory of Alpha Particle Decay

Gamow’s Theory of Alpha Particle Decay was initially formulated for a limited set of nuclei. In this study, the researchers extend the scope and assessed the applicability of the theory to a broader range of nuclides especially those with different proton and neutron compositions. Three objectives were formulated to undertake the research. The researcher utilized one-dimensional WKB approximation to calculate the probability of tunneling through the potential barrier, which is a simplification compared to other formulas. The Geiger-Nuttall law, which describes a dependence of the disintegration constant on the range of α-particles, was deduced using the Gamow theory describing the passage of the α-particles through the Coulomb barrier by the quantum mechanical tunneling effect. Ground-to-ground state α-transitions for α-active nuclides were analyzed based on their half-lives and their dependence on various factors. The study revealed that all α-active nuclides whose Z ranges between 70 to100 undergoes similar alpha decay processes.

Ra-223 induces clustered DNA damage and inhibits cell survival in several prostate cancer cell lines

The bone-seeking radiopharmaceutical Xofigo (Radium-223 dichloride) has demonstrated both extended survival and palliative effects in treatment of bone metastases in prostate cancer. The alpha-particle emitter Ra-223, targets regions undergoing active bone remodeling and strongly binds to bone hydroxyapatite (HAp). However, the toxicity mechanism and properties of Ra-223 binding to hydroxyapatite are not fully understood. By exposing 2D and 3D (spheroid) prostate cancer cell models to free and HAp-bound Ra-223 we here studied cell toxicity, apoptosis and formation and repair of DNA double-strand breaks (DSBs). The rapid binding with a high affinity of Ra-223 to bone-like HAp structures was evident (KD= 19.2 × 10−18 M) and almost no dissociation was detected within 24 h. Importantly, there was no significant uptake of Ra-223 in cells. The Ra-223 alpha-particle decay produced track-like distributions of the DNA damage response proteins 53BP1 and ɣH2AX induced high amounts of clustered DSBs in prostate cancer cells and activated DSB repair through non-homologous end-joining (NHEJ). Ra-223 inhibited growth of prostate cancer cells, independent of cell type, and induced high levels of apoptosis. In summary, we suggest the high cell killing efficacy of the Ra-223 was attributed to the clustered DNA damaged sites induced by α-particles.

Computer simulation and description of alpha particle decay and isotope separation

The computer simulation features of the alpha particle decay and isotope separationare discussed in presented paper. When positively charged alpha particles hit a thin plate of matter, then at a close distance to the nuclei they are repelled from the nucleus of an atom, deviating from a straight line in motion, and can even change the rectilinear motion, strongly repulsing from the nucleus and moving towards the source of alpha particles. These cases are simulated and graphs of the trajectories of alpha particles are plottedusing modern computer mathematical system Mathcad.It is proposed to compose differential equations describing the trajectory of the alpha particle and solve them by using the Bulstoer function in the Mathcad. The simulations perfectly confirm the predicted behavior of particles some of them deviate from their linear motion in the absence of a nucleus, and some of the particles change direction in the opposite one. Particle sensors installed in different parts of the physical device detect such changes in the trajectory, which is a confirmation of the atomic theory of the structure of matter and materials. An application program for describing the spectroscopic method of isotope separation has been developed and discussed in detail. Of course, the described models cannot be considered absolutely accurate. For example, if the particles are aimed exactly at the nucleus, significant errors can occur. If the particle speed is high, then the particles can overcome the repulsive force of the nucleus, causing the particles to be absorbed by them. Such absorption conditions are not taken into account in the developed models. One of the important tasks of nuclear physics is the separation of isotopes. An application program has been developed to describe the spectroscopic method of isotope separation. This method is based on the characteristics of the trajectory of ions that radiate and oscillate under an impact of a magnetic field. A system of differential equations describing the motion of ions is given. The problem of the motion of electrically charged particles in a uniform magnetic field is solved in the Mathcad.

Electromagnetic-radiation effect on alpha decay

The effect of the electromagnetic radiation on the spontaneous charge emission from heavy atomic nuclei is estimated in a model which may be relevant for proton emission and alphaparticle decay in laser fields. Arguments are given that the electronic cloud in heavy atoms screens appreciably the electric field acting on the nucleus and the nucleus “sees” rather low fields. In these conditions, it is shown that the electromagnetic radiation brings second-order corrections in the electric field to the disintegration rate, with a slight anisotropy. These corrections give a small enhancement of the disintegration rate. The case of a static electric field is also discussed.

Experimental survey of the production of α -decaying heavy elements in U238+Th232 reactions at 7.5–6.1 MeV/nucleon

The production of alpha particle decaying heavy nuclei in reactions of 7.5-6.1 MeV/nucleon $^{238}$U +$^{232}$Th has been explored using an in-beam detection array composed of YAP scintillators and gas ionization chamber-Si telescopes. Comparisons of alpha energies and half-lives for the observed products with those of the previously known isotopes and with theoretically predicted values indicate the observation of a number of previously unreported alpha emitters. Alpha particle decay energies reaching as high as 12 MeV are observed. Many of these are expected to be from decay of previously unseen relatively neutron rich products. While the contributions of isomeric states require further exploration and specific isotope identifications need to be made, the production of heavy isotopes with quite high atomic numbers is suggested by the data.

In-line (α,n) source sampling methodology for monte carlo radiation transport simulations

Abstract A new in-line method for sampling neutrons emitted in (α,n) reactions based on alpha particle source information has been developed for continuous-energy Monte Carlo simulations. The new method uses a continuous-slowing-down model coupled with (α,n) cross section data to precompute the expected neutron yield over the alpha particle lifetime. This eliminates the complexity and computational cost associated with explicit charged particle transport. When combined with an integrated alpha particle decay source sampling capability, the proposed method provides an efficient and accurate method for sampling (α,n) neutrons based solely on nuclide inventories in the problem, with no additional user input required. Results from several example calculations show that the proposed method reproduces the (α,n) neutron yields and energy spectra from reference experiments and calculations.

The Radiochemical and Radiopharmaceutical Applications of Radium

AbstractThis review focuses on the chemistry and application of radium isotopes to environmental monitoring, analytical, and medicinal uses. In recent years, radium has been used primarily as a tracer to study the migration of radioactive substances in environmental systems. Tracing the naturally occurring radium isotopes in mineral and water sources allows for the determination of source location, residence time, and concentrations. An understanding of the concentration of radionuclides in our food and water sources is essential to everyone’s health as alpha particle decay is highly damaging in vivo. Due to this high radiobiological effectiveness, there is increased interest in using alpha-emitting radionuclides to prepare new, therapeutic radiopharmaceutical drugs. Selected studies from the recent literature are provided as examples of these modern applications of radium isotopes.

Measurement of the 226Th and 222Ra half-lives

The half-lives of 226Th and 222Ra were measured by counting alpha-particle emissions from sources as a function of time. The 226Th sources were prepared from an open 230U source, capturing recoil atoms after alpha-particle decay on glass disks or even directly onto a detector. Similarly, the 222Ra sources were obtained by self-transfer of recoil atoms from 226Th sources. The activity measurements were performed in (nearly-)2π geometry with an ion-implanted silicon detector. The decay curves were analysed in different ways, incl. moment analysis, trying to avoid the pitfalls of bias of least-squares fits to Poisson distributed data. The observed half-life values are T1/2(226Th)=30.70 (3) min and T1/2(222Ra)=33.6 (4) s. Literature values show some inconsistency.

Alpha-particle decays from excited states in 24Mg

Using a cluster model based on the Woods-Saxon potential, alpha-particle decays from excited states in 24Mg have been systematically investigated. Calculations can in general reproduce experimental data, noticing the fact that the preformation factor P of alpha particle in alpha-decaying nuclei is of order from 100 to 10−2. This can be the evidence for the α+20Ne structure in 24Mg. Meanwhile, the results also show the existence of other configurations, such as 16O+2α. Since the calculated decay widths are very sensitive to the angular momentum carried by the outgoing cluster (α particle), our results could serve as a guide to experimental spin assignments.

Lightest Isotope of Bh Produced via theBi209(Cr52,n)Bh260Reaction

The lightest isotope of Bh was produced in the new 209Bi(52Cr,n)260Bh reaction at the Lawrence Berkeley National Laboratory's 88-Inch Cyclotron. Positive identification was made by observation of eight correlated alpha particle decay chains in the focal plane detector of the Berkeley Gas-Filled Separator. 260Bh decays with a 35(-9)(+19) ms half-life by alpha particle emission mainly by a group at 10.16 MeV. The measured cross section of 59(-20)(+29) pb is compared to model predictions. The influence of the N=152 and Z=108 shells on alpha decay properties is discussed.

Emergent magnetic moments produced by self-damage in plutonium.

Plutonium possesses the most complicated phase diagram in the periodic table, driven by the complexities of overlapping 5f electron orbitals. Despite the importance of the 5f electrons in defining the structure and physical properties, there is no experimental evidence that these electrons localize to form magnetic moments in pure Pu. Instead, a large temperature-independent Pauli susceptibility indicates that they form narrow conduction bands. Radiation damage from the alpha-particle decay of Pu creates numerous defects in the crystal structure, which produce a significant temperature-dependent magnetic susceptibility, chi(T), in both alpha-Pu and delta-Pu (stabilized by 4.3 atomic percent Ga). This effect can be removed by thermal annealing above room temperature. By contrast, below 35 K the radiation damage is frozen in place, permitting the evolution in chi(T) with increasing damage to be studied systematically. This result leads to a two-component model consisting of a Curie-Weiss term and a short-ranged interaction term consistent with disorder-induced local moment models. Thus, it is shown that self-damage creates localized magnetic moments in previously nonmagnetic plutonium.

A contribution to improvement of the nuclear data concerning alpha decay of 235U

Compared to other alpha-particle emitting nuclides, for those with long half-lives ( T 1 / 2 > 1 0 6 years), there is generally some inconsistency and inaccuracy in the associated nuclear data. However, these radionuclides play a major role in modern society and, for a number of reasons, are the subject of widespread interest. The study of their alpha decay , which is more difficult than in the case of the other nuclides, enables knowledge of their nuclear data to be increased. In the present paper, we accordingly consider one of the most well known ones: 235 U. Using a quasi mono-isotopic deposit of 235 U obtained by electromagnetic separation, we have studied the alpha-particle decay of 235 U using a high-energy resolution spectrometer developed in our laboratory. The stability of the spectrometer made it possible to perform long measurements which is crucial in the case of 235 U. The Colégram program, with a new fit criterion to better take into account peaks of low statistical significance, was used to extract the data (alpha-particle emission probabilities and energies). Monte-Carlo simulations carried out in the context of this work were also used to corroborate the data obtained. Finally, thirteen alpha-particle emissions from 235 U were measured, from which only ten were previously observed and measured. This work has substantially reduced the uncertainty concerning alpha-particle emission probability and energy values and has resolved some of the ambiguities concerning the 235 U disintegration scheme to 231 Th.

A contribution to improvement of the nuclear data concerning alpha decay of 235U

Compared to other alpha-particle emitting nuclides, for those with long half-lives (T1/2>106 years), there is generally some inconsistency and inaccuracy in the associated nuclear data. However, these radionuclides play a major role in modern society and, for a number of reasons, are the subject of widespread interest. The study of their alpha decay, which is more difficult than in the case of the other nuclides, enables knowledge of their nuclear data to be increased. In the present paper, we accordingly consider one of the most well known ones: 235U. Using a quasi mono-isotopic deposit of 235U obtained by electromagnetic separation, we have studied the alpha-particle decay of 235U using a high-energy resolution spectrometer developed in our laboratory. The stability of the spectrometer made it possible to perform long measurements which is crucial in the case of 235U. The Colégram program, with a new fit criterion to better take into account peaks of low statistical significance, was used to extract the data (alpha-particle emission probabilities and energies). Monte-Carlo simulations carried out in the context of this work were also used to corroborate the data obtained. Finally, thirteen alpha-particle emissions from 235U were measured, from which only ten were previously observed and measured. This work has substantially reduced the uncertainty concerning alpha-particle emission probability and energy values and has resolved some of the ambiguities concerning the 235U disintegration scheme to 231Th.

Etching of recoil tracks in solids

Low-energy (keV/atomic mass) ions in solids displace atoms, producing damage sites that are often described as tracks. Common natural sources of such tracks are recoiling residual nuclei from natural alpha-particle decay. Different models of such tracks are noted and compared with existing experimental results. First, the drastically lower rates of etching along such tracks in muscovite mica, compared to those for continuous ionization-produced tracks (such as result from fission), imply that recoil tracks are discontinuous, with clumped damage that is interrupted by gaps that either are undamaged, or lightly damaged. Second, based on the size of recoil-tracks and the numbers that bring about total disorder in crystals such as zircon, the tracks are diffuse regions–containing only about 2% of misplaced atoms. A simple model describes the profound effect of the gaps in recoil tracks on etching efficiency, removal of recoil nuclei by leaching, track revelation, and their vastly different etching behavior from that of high-energy tracks.

First observation of gamma-rays from the proton emitter 171Au

Gamma-rays from the alpha- and proton-unstable nuclide 171Au have been observed for the first time. The gamma-rays were correlated with both a proton- and an alpha-particle decay branch, confirming that the nucleus decays by alpha and proton emission from a single (11/2-) state. The measurement confirms the previously determined half-lives for these particle decays but the present values are of higher precision. In addition, a longer half-life than determined in previous work was measured for the proton-unstable tentative ground state. The results are discussed in relation to structures in neighbouring nuclei and compared with a Strutinsky-type TRS calculation.

Depleted uranium-catalyzed oxidative DNA damage: absence of significant alpha particle decay

Depleted uranium (DU) is a dense heavy metal used primarily in military applications. Published data from our laboratory have demonstrated that DU exposure in vitro to immortalized human osteoblast cells (HOS) is both neoplastically transforming and genotoxic. DU possesses both a radiological (alpha particle) and a chemical (metal) component. Since DU has a low-specific activity in comparison to natural uranium, it is not considered to be a significant radiological hazard. In the current study we demonstrate that DU can generate oxidative DNA damage and can also catalyze reactions that induce hydroxyl radicals in the absence of significant alpha particle decay. Experiments were conducted under conditions in which chemical generation of hydroxyl radicals was calculated to exceed the radiolytic generation by 106-fold. The data showed that markers of oxidative DNA base damage, thymine glycol and 8-deoxyguanosine could be induced from DU-catalyzed reactions of hydrogen peroxide and ascorbate similarly to those occurring in the presence of iron catalysts. DU was 6-fold more efficient than iron at catalyzing the oxidation of ascorbate at pH 7. These data not only demonstrate that DU at pH 7 can induced oxidative DNA damage in the absence of significant alpha particle decay, but also suggest that DU can induce carcinogenic lesions, e.g. oxidative DNA lesions, through interaction with a cellular oxygen species.

Theory of nuclear reactions and decays with allowance for antisymmetrization effects

On the basis of an explicit implementation of the projection-operator method and with due regard to antisymmetrization effects, formulas are constructed for the amplitudes of elastic and inelastic nuclear reactions induced by nucleons and composite particles and for the widths with respect to the nucleonic, alpha-particle, and cluster decays of nuclei. It is shown that equations governing the behavior of elastic-scattering form factors represent generalizations of the equations of the resonating-group model and coincide, provided that ground-state correlations are taken into account, with the analogous equations in the theory of open Fermi systems. It is demonstrated that the nonretarded part of the effective potential of nucleus-nucleus interaction coincides with the Hartree-Fock potential, which has a deep attractive character in accordance with the Levinson theorem, and that the retarded part of the effective potential is determined by the fragmentation of the initial states of colliding nuclei into compound states. It is revealed that the use of different elastic-form-factor representations associated with taking into account antisymmetrization effects leads to the same results for the amplitudes of elastic and inelastic nuclear reactions. The formulas obtained here for the amplitudes of direct inelastic nuclear reactions are found to differ significantly from the corresponding formulas of the distorted-wave method in the Born approximation. Problems that are concerned with the emergence of potential optical resonances for elastic form factors and with their relation to the shell-model wave functions for a compound system are investigated. A new regime of interpolation for the amplitudes of cluster form factors from the shell to the asymptotic region of a decaying nucleus is found. Implications of this interpolation for the calculated alpha-particle and cluster widths and for understanding the nature of superfluid correlations in nuclei are analyzed.

Nuclear Data Sheets for A = 267–293

These data are mainly from cold fusion experiments performed at GSI/Ship, Dubna, and Berkeley. The experiments generally involve mass separation of heavy elements followed by implantation into a position–sensitive alpha–particle detector. The position, energy, and time with respect to implantation are recorded. Successive decays at a given position are correlated into a decay chain linking the heaviest cold fusion product to lighter nuclei which also may be previously unknown. In some cases the decay chain ends in spontaneous fission, and some alpha particles escape the detector leaving only partial energy signals. When multiple alpha decay chains are observed for a given parent, the evaluators have made subjective assignments to isomer and ground states based on comparable alpha particle energies and decay times.

Personal monitoring of 218Po and 214Po radionuclide deposition onto individuals under normal environmental exposure conditions

Personal dosemeters have been utilized to monitor the deposition of the radon decay products 218Po and 214Po onto individuals under normal environmental exposure conditions. Each detector consists of TASTRAK alpha-sensitive plastic incorporated into an ordinary working wristwatch. Subsequent analysis provides energy discrimination of the detected alpha-particle decays, and allows events from the individual radon decay products 218Po and 214Po, attached to the detector surface, to be uniquely identified. Assuming similar deposition onto skin and detector surfaces, the activity per unit area of deposited radionuclides can be determined for exposed skin. Forty-one personal dosemeters were issued to volunteers selected through the hospital medical physics departments at Reading, Northampton, Exeter and Plymouth. Each volunteer was also issued with a personal radon dosemeter to determine their individual radon exposure. The volunteers wore the two dosemeters simultaneously and continuously for a period of around one month. Correlations were observed between the radon exposure of the individual and the activity per unit area of 218Po and 214Po on the detector surface. From these correlations it can be estimated that at the UK average radon exposure of 20 Bq m-3, the number of decays/cm2/year on continuously exposed skin surface is between 3500 and 28 000 for 218Po, and between 7000 and 21 000 for 214Po. These results can be combined with theoretical modelling of the dose distribution in the skin to yield the alpha-particle radiation dose to any identified target cells.

Radiotoxicity of plutonium in NTA-degrading Chelatobacter heintzii cell suspensions.

The radiotoxicity of plutonium in NTA-degrading Chelatobacter heintzii cell suspensions was investigated as part of a more general study to establish the key interactions between actinide-organic complexes and microorganisms in the subsurface. The radiation tolerance of C. heintzii, based on 60Co gamma irradiation experiments, was 165 +/- 30 Gy. No bacteria survived irradiation doses greater than 500 Gy. In the presence of plutonium, where alpha particle decay was the primary source of ionizing radiation, the observed toxicity was predominantly radiolytic rather than chemical. This was evident by the greater effect of activity, rather than concentration, on the toxicity noted. Bioassociation of plutonium with C. heintzii was postulated to be an important and necessary step in the observed loss of cell viability since this was the best way to account for the observed death rate. The radiotoxicity of plutonium towards bacteria is a potentially important consideration in the bioremediation of sites contaminated with radionuclide-organic mixtures and the bioprocessing of nuclear waste.