alpha decay

The alpha decay, the cluster radioactivity and the heavy particle emission half-lives of known and some still unknown superheavy nuclei have been investigated within the original Generalized Liquid Drop Model and analytic formulas. The Q value has been calculated mainly from the recent NUBASE2020 tables. The agreement between the experimental data and the theoretical predictions of the alpha decay half-lives of the superheavy nuclei is correct and some predictions are provided for unknown nuclei. For some emissions of heavy particles by superheavy nuclei the half-life is comparable to the alpha decay half-lives or even smaller.

The 2p radioactivity half-lives have been calculated within a tunneling process through the potential barrier determined from the original version of the generalized liquid drop model and quasimolecular shapes. The sparse experimental data on the 2p radioactivity half-lives of the 12 O, 16 Ne, 19 Mg, 45 Fe, 48 Ni, 54 Zn, and 67 Kr nuclei are roughly reproduced when taking into account the Q exp 2p value. An analytic formula is provided to obtain rapidly these different half-lives. Using the Q 2p values extracted from the recent Nubase2020 table, extrapolations to other perhaps possible 2p emitters are proposed. Within the same approach, formulas to determine the 9 Be, 6,7 Li, 3,6 He, and 2,3 H decay half-lives at low excitation energy are also provided.

The potential barriers in the cold fission valley were determined within the original generalized liquid drop model, which takes into account the proximity energy, the charge and mass asymmetries, the microscopic shell and pairing corrections, and quasimolecular one-and two-body shapes. Due to microscopic effects and the proximity energy, double-humped fission barriers appear. The calculations were done within four hypotheses for the heaviest proton magic number: 114, 116, 118, and 120. The calculated partial or total fission half-lives of actinides and superheavy nuclei follow roughly the trend of the experimental data, the agreement being better for Z = 118.

The longitudinal ternary fission is studied using the generalized liquid drop model. The proximity energy and the charge and mass asymmetries are taken into account. Spherical parent and daughter nuclei are considered. The shape sequence selected to simulate the quasimolecular three-body shapes is built from different but connected elliptic half lemniscatoids. The potential barriers are much lower when the central fragment is the smallest one and particularly when it is an α particle. The 2α emission can be described as a particular prolate fission with emission of two particles at the tips of the deformed nucleus. The associated potential barriers are high and thin.

Half lives of alpha decay for odd-even isotopes of Am 231-245 , Es 239-257 and Md 245261 nuclei from ground state to ground and excited states of daughter nuclei have been calculated using CYE model. In this work we take into account of both quadruple (β2) and hexadecapole (β4) deformations, as well as the spinparity of parent and daughter nuclei. The calculated half-lives are compared with available data and are found to be good agreement with each other. The Hindrance factor and branching ratios to the excited states of daughter nucleus also determined. The influence of alpha decay energy and the angular momentum of alpha particle on the half-life time calculation have been studied. The standard deviation value for half-life is computed.

Nuclei in the actinide region are good in exhibiting cluster radioactivity. In the present work, the half-lives of α-decay and heavy cluster emission from certain actinide nuclei have been calculated using cubic plus Yukawa plus exponential model (CYEM). Our model has a cubic potential for the overlapping region which is smoothly connected by a Yukawa plus exponential potential for the region after separation. The computed half-lives are compared with those of other theoretical models and are found to be in good agreement with each other. In this work, we have also studied the deformation effects on half-lives of cluster decay. These deformation effects lower the half-life values and it is also found that the neutron-rich parent nuclei slow down the cluster decay process. Geiger-Nuttal plots for various clusters are found to be linear and most of the emitted clusters are α-like nuclei.

The potential energy governing α emission has been determined within a liquid drop model including proximity effects between the α particle and the daughter nucleus and adjusted to reproduce the experimental Q α. The α emission half-lives have been deduced from the WKB barrier penetration probability as for a spontaneous asymmetric fission. The RMS deviation between the theoretical and experimental values of log 10 [T 1/2 (s)] is only 0.63 for a recent data set of 373 α emitters and 0.35 for the subset of even-even nuclides. Predictions for the heaviest and superheavy elements are presented as well as simple analytical formulae for log 10 [T 1/2 (s)].

The potential energy governing alpha emission has been determined within a liquid drop model including proximity effects between the alpha particle and the daughter nucleus and adjusted to reproduce the experimental Qalpha. The alpha emission half-lives have been deduced from the WKB barrier penetration probability as for a spontaneous asymmetric fission. The RMS deviation between the theoretical and experimental values of log 10[T1/2(s)] is only 0.63 for a recent data set of 373 alpha emitters and 0.35 for the subset of even-even nuclides. Predictions for the heaviest and superheavy elements are presented as well as simple analytical formulae for log 10[T1/2(s)].

GUINEVERE is a low power accelerator driven system (ADS) consisting of a versatile neutron source, GENEPI-3C, driving the fast sub-critical core, VENUS-F, in SCK•CEN (Belgium). GENEPI-3C is an electrostatic accelerator generating 14 MeV neutrons by bombarding a 250 keV deuteron beam onto a tritium target located within the reactor core. This accelerator produces alternatively continuous beam (up to 1 mA DC), possibly chopped with fast and adjustable interruptions, or short and intense deuteron bunches (~25 mA peak, 1 μs). This paper presents the facility and assesses the 2 years of coupled operation of the accelerator to the reactor.

It is shown that the proton formation probabilities, extracted from experimental decay half-lives, can be well reproduced by a simple multilinear formula with only three parameters. The parameters obtained by considering the standard root mean square deviation and the mini-max criteria are very similar to each other. In addition, we applied Bayesian analysis to study the uncertainties of the parameters and the model predictions. In this way we explain the systematics of proton decay half-lives. The multilinearity of the model also provides a way to classify the relative hindrance of different proton decays. All the recent experimental data agree very well with the model prediction. Our Bayesian analysis suggests that those new data do help constrain the uncertainty of the model parameters.

The resonance shapes were reproduced well with the GDR shape observed in the 4 He͑␥ , n͒ reactions. The averaged value for the ratios of the resonance cross section in A = 6 to that in A = 7 for each element was 1.2± 0.3. The averaged value for the ratios of the resonance cross section to the GDR cross section in the respective target nuclei was 0.44± 0.08, which was consistent with the ratios of the GDR cross section in 4 He to that in 6,7 Li reported in the photonuclear reactions. The excitation energies for the dipole resonances in A = 6 and 7 nuclei relative to the separation energies of an ␣ particle in 6 Li and 7 Li, respectively, agreed well with the excitation energy for the GDR in 4 He ͑ϳ26 MeV͒. We conclude that the resonances observed in 6,7 Li are consistent with the GDR of the ␣ cluster and the resonances in 6,7 He and 6,7 Be are consistent with the analogs of the GDR in the ␣ cluster. The Q value for the excitation of the GDR of the ␣ cluster in A = 7 nuclei is deeper by 1.6± 0.3 MeV on the average than that in A =6.

The decay of the isotopes 255 Rf, 251 No and 247 Fm produced in the reactions 207 Pb( 50 Ti, 2n) 255 Rf α → 251 No α → 247 Fm, and 206 Pb( 48 Ca, 3n) 251 No α → 247 Fm was investigated by means of α-γ spectroscopy. Previously observed γ transitions in coincidence with α decays of 255 Rf were confirmed, their energies and line intensities were measured more precisely, and their multipolarities were determined as E1. In 251 No a new isomeric state at E * > 1700 keV with a half-life of ≈ 2 µs was identified. The decay of 247 Fm was measured more precisely. A partial level scheme of the daughter nucleus 243 Cf could be established.

Self-irradiation can affect durability of glasses used to immobilize high-level nuclear waste (HLW). The stability of glasses can also be indirectly affected by the radiolytic changes in contact water leading to decrease in its pH although this is unlikely to occur for disposal systems where the interaction of groundwater with glass is delayed to times when radiation dose rates are decreased to levels insignificant to cause such effects. Besides, interaction of the water influenced by radiation with other repository protective elements (container and bentonite) will suppress the radiolytic changes. Literature analysis shows practical absence or very weak effect of self-irradiation on structure and characteristics of borosilicate glasses with typical content of nuclear waste. Data for aluminophosphate glass used in Russia have showed that, after γ-irradiation with a dose of 6.2·107 Gy, the leaching rates of elements were decreased approximately twice relatively to pristine samples.

We have studied 12 C in full kinematics via the 10 B( 3 He,pααα) reaction at 2.45 MeV. In our data we have identified states in 12 C from the ground state up to about 18 MeV, with spins ranging from 0 to 4. Due to the very good resolution, we are able to determine properties of these 12 C resonances, such as their energy, width, and spin. In this contribution preliminary results from the ongoing analysis is presented.

We have used the 10 B( 3 He, pααα) reaction at 4.9 MeV and the 11 B( 3 He, dααα) reaction at 8.5 MeV to determine the energy, width, and decay mechanism of resonances in 12 C above the triple-α threshold up to 21 MeV in excitation energy. Comparison with various models has allowed us to estimate the degree of clustering of the states studied.

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. Recent experiments have triggered a great interest in the phenomena of bremsstrahlung during tunneling processes which was discussed from different theoretical viewpoints in . This can shed light on basic and still controversial quantum-mechanical problems of tunneling times [5], especially in a complex and nonstationary environment. It seems that α-decay offers a unique possibility to study these fundamental questions. In ref. [1] it was claimed that the bremsstrahlung spectrum in alpha-decay of 210 Po could provide information about the tunneling time. Their claim is based on the comparison of the experimental spectra with a semiclassical calculation of Dyakonov and Gornyi , which shows an interference pattern arising from the contributions to bremsstrahlung from the inner, under the barrier, and outer parts of the wave function. Papenbrock and Bertsch [3] performed a quantum-mechanical calculation for the bremsstrahlung in α-decay in perturbation theory. They have shown that the contribution from the tunneling wave function under the barrier is small, as well as the appearance of interference effects in the spectrum. The greater effect, as expected, arises from the Coulomb acceleration of the α-particle outside the nuclear well. Later, Takigawa et al. [4] compared the quantum-mechanical calculations with classical and semiclassical results. They conclude that subtle interferences of contributions from different parts of the wave function do indeed arise. However, in both cases, the authors infer that the experimental data are not conclusive. More exclusive experiments, with better statistics, are needed to give a clearer understanding of the phenomena. The theoretical approaches of refs. assume a standard stationary description of quantum tunneling which is very successful for α-decay lifetime and probabilities. However, a time dependent picture of a decay process may be essential in understanding physics of the bremsstrahlung and similar processes, in particular in obtaining the appropriate bremsstrahlung spectrum. This can be shown, for example, by looking into a case where there is no Coulomb acceleration after the tunneling. In this letter we model the time evolution of the wave function during the tunneling using again α-decay as an example. We do not attempt to compare our results with the experimental data. The reason is simple: the α-decay time, e.g., the lifetime of 210 Po, is many orders of magnitude larger than typical times for an α-particle to traverse across the nucleus. This implies that a stable numerical solution of the Schrödinger equation, keeping track simultaneously of fast oscillations in the well ("escape attempts") and extremely slow tunneling, is virtually impossible: for 210 Po it would require about 10 30 time steps in the iteration process. Instead, we study the bremsstrahlung in high energy α-decays, for which the decay time is treatable numerically. This allows us to pay attention to qualitatively new aspects of the bremsstrahlung in decay processes, and compare with traditional aproaches. For an α-particle being accelerated from the turning point to infinity, the classical bremsstrahlung can be calculated analytically. Using the well known equations, see for example , and integrating along the outward branch of the Rutherford trajectory in a head-on collision we get for the energy emitted by bremsstrahlung per frequency interval dω, in the long-wavelength approximation,

We re-examined Shlyakhter's analysis of the Sm data in Oklo. With a special care of minimizing contamination due to the inflow of the isotope after the end of the reactor activity, we confirmed that his result on the time-variability of the fine-structure constant, la/al;S1O-17 y-1, was basically correct. In addition to this upper bound, however, we obtained another result that indicates a different value of a 2 billion years ago. We add comments on the recent result from QSO's.

Short-lived α-decaying nuclei 'North-East' of 208 Pb in the chart of nuclides were studied using the reaction 48 Ca + 243 Am with the decay station TASISpec at TASCA, GSI Darmstadt. Decay energies and times from pile-up events were extracted with a tailor-made pulse shape analysis routine and specific α-decay chains were identified in a correlation analysis. Decay chains starting with the even-even 220 Ra and its odd-A neighbors, 219 Fr, and 221,219 Ra, with a focus on the 219 Ra→ 215 Rn decay, were studied by means of α-γ spectroscopy. A revised α-decay scheme of 219 Ra is proposed, including a new decay branch from a previously not considered isomeric state at 17 keV excitation energy. Conclusions on nuclear structure are drawn from the experimental data, aided by Geant4 simulations and a discussion on theoretical calculations.

Products of the fusion-evaporation reaction 48 Ca + 243 Am were studied with the TASISpec set-up at the gas-filled separator TASCA at the GSI Helmholtzzentrum für Schwerionenforschung. Amongst the detected thirty correlated α-decay chains associated with the production of element Z = 115, two recoil-α-fission and five recoil-α-α-fission events were observed. The latter are similar to four such events reported from experiments performed at the Dubna gas-filled separator. Contrary to their interpretation, we propose an alternative view, namely to assign eight of these eleven decay chains of recoil-α(-α)-fission type to start from the 3n-evaporation channel 288 115. The other three decay chains remain viable candidates for the 2n-evaporation channel 289 115.

The structure of the 18 O nucleus at excitation energies above the α decay threshold was studied using 14 C + α resonance elastic scattering. A number of states with large α reduced widths have been observed, indicating that the α-cluster degree of freedom plays an important role in this N = Z nucleus. A 0 + state with an α reduced width exceeding the single-particle limit was identified at an excitation energy of 9.9 ± 0.3 MeV. We discuss evidence that states of this kind are common in light nuclei and give possible explanations of this feature.

The actinide-containing mineral monazite–(Ce) is a common accessory rock component that bears petrogenetic information, is widely used in geochronology and thermochronology, and is considered as potential host material for immobilisation of radioactive waste. Natural samples of this mineral show merely moderate degrees of radiation damage, despite having sustained high self-irradiation induced by the decay of Th and U (for the sample studied herein 8.9 ± 0.3 × 1019 α/g). This is assigned to low damage-annealing temperature of monazite–(Ce) and “alpha-particle-assisted reconstitution”. Here we show that the response of monazite–(Ce) to alpha radiation changes dramatically, depending on the damage state. Only in radiation-damaged monazite–(Ce), 4He ions cause gradual structural restoration. In contrast, its high-temperature annealed (i.e. well crystalline) analogue and synthetic CePO4 experience He-irradiation damage. Alpha-assisted annealing contributes to preventing irradiation-indu...

This paper brings together the most important aspects of nuclear structure and reaction dynamics that may have an influence on stability of superheavy nuclei. These aspects form the basis of current experimental research on heaviest elements to investigate their basic properties. The shell model is used to estimate microscopically the alpha formation amplitude from single quasiparticle states under the influence of the pairing interaction. Half-life calculations for fission are performed in a dynamical approach defined by the shape and the high of fission barrier, the fissility and nuclear deformations. Reaction energies Q S F are estimated within the liquid drop model. We predicted with the most probable total half-lives for many unknown nuclides at which there are no experimental data. The rms values for experimental and theoretical half-lives are evaluated and discussed. The comparison of theoretical calculations with experimental data allows us to draw conclusions on the role of the nuclear structure and shell effects in low-energy decay processes.

The barriers standing against the formation of superheavy elements and their consecutive α decay have been determined in the quasimolecular shape path within a Generalized Liquid Drop Model including the proximity effects between nucleons in a neck, the mass and charge asymmetry, a precise nuclear radius and the shell effects given by the Droplet Model. For moderately asymmetric reactions doublehump potential barriers stand and fast fission of compact shapes in the outer well is possible. Very asymmetric reactions lead to one hump barriers which can be passed only with a high energy relatively to the superheavy element energy. Then, only the emission of several neutrons or an α particle can allow to reach an eventual ground state. For almost symmetric heavy-ion reactions, there is no more external well and the inner barrier is higher than the outer one. Predictions for partial α decay half-lives are given.

Charged particle spectroscopy can provide insight into the nuclear structure of exotic nuclei. Far away from the valley of stability nuclei become difficult to produce and observe. Short lifetimes and low count rates make experiments very challenging. One way to do these experiments is by implanting a nucleus into a silicon detector and observing its alpha or proton decay. At

The neutron capture cross section of 206 Pb has been measured at the CERN n TOF spectrometer using a setup of two C 6 D 6 detectors. In the energy interval from 1 eV to 600 keV the cross section is dominated by resonances, which were analyzed via the R-matrix analysis code SAMMY. In the relevant energy ranges for stellar nucleosynthesis, i.e., at thermal energies of kT = 8 keV and kT = 23 keV, the present Maxwellian average cross section differs by 20% and 9% from the recommended values of Bao et al respectively. From the new cross section the s-abundance of 206 Pb could be reliably determined as 70(4)%. This result is of importance in order to test and constrain r-process abundance calculations in the actinide region, because the r-process portion of 206 Pb is dominated by α-back decays of short-lived transbismuth isotopes.

A detailed study of α-clusters decay is exhibited by incorporating crucial microscopic nuclear structure information into the estimations of half-life and preformation factor. For the first time, using the k-cross validation approach, two semi-empirical formulas for (i) α-decay half-life and (ii) α-particle preformation factor, are picked out and subsequently modified by including shell, odd-nucleon blocking, and asymmetry effects along with the usual dependence on α-decay energy (Q α) and angular momentum of α-particle. Both the formulas are fitted for the two different regions separated by neutron number N=126, as from the experimental systematics the role of N=126 shell closure is found decisive in determining the trends of Q α , α-decay half-life, and α-particle preformation factor. It is found that the inclusion of the above-mentioned degrees of freedom significantly reduces the errors in the estimations when compared with several other similar modified/refitted semi-empirical relations indicating the robustness of the proposed formulas. The predictions of α-decay half-life throughout the periodic chart have been made including the unknown territory, future probable decay chain of self-conjugate nucleus 112 Ba terminated on 100 Sn, decay chain of 208 Pa through new isotope 204 Ac as well as decay chains of awaiting superheavy nuclei 298 Og and 299 120. This article is expected to provide a systematic approach to selecting the formula by which reliable predictions can be made.

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 alpha-particle 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.

Artificial neural networks are trained by a standard backpropagation learning algorithm with regularization to model and predict the systematics of -decay of heavy and superheavy nuclei. This approach to regression is implemented in two alternative modes: (i) construction of a statistical global model based solely on available experimental data for alpha-decay half-lives, and (ii) modeling of the {\it residuals} between the predictions of state-of-the-art phenomenological model (specifically, the effective liquid-drop model (ELDM)) and experiment. Analysis of the results provide insights on the strengths and limitations of this application of machine learning (ML) to exploration of the nuclear landscape in regions beyond the valley of stability.

The decay dynamical path is determined within the macroscopic-microscopic model for the emission of 24Ne from 232U. The nuclear shape parametrization is characterized five degrees of freedom. The single particle energies and the nucleon wave functions are obtained within the superasymmetric Woods-Saxon two center shell model. It turns out that the cluster decay follows a potential magic valley, starting from the ground state of the parent and reaching a configuration of two touching nuclei at scission. A small pocket in the potential barrier is evidenced, as a result of large shell effects in the nascent fragments. The half-life is computed by using several approaches for the effective mass. It is shown that the inertia within by the gaussian overlap approach gives the closest values to the experimental ones. Half-lives for different cluster decays are predicted. The theoretical values are compared to various phenomenological estimates.

Detailed α-decay studies of 179 Tl g and its daughter products 175 Au g and 171 Ir g were carried out in two complementary experiments at the mass separator ISOLDE (CERN) and velocity filter SHIP (GSI). First unambiguous determination of the α-decay properties of 175 Au g was performed as follows: E α = 6433(4) keV, T 1/2 = 207(7) ms, and α-decay branching ratio 90(7)%. First determination of the α-decay branching ratios for 179 Tl g and 171 Ir g was also made: b α (179 Tl g) = 60(2)% and b α (171 Ir g) = 15(2)%. The spins of the ground states in 175 Au and 171 Ir are established as 1/2 + .

Making use of effective liquid drop model (ELDM)[1], the feasibility of proton and alpha decays and various cluster decays is analysed theoretically. For different neutron-rich and neutron-deficient isotopes of Rhenium in the mass range 150 < A < 200, the half lives of proton and alpha decays and probable cluster decays are calculated considering the barrier potential as the effective liquid drop one which is the sum of Coulomb, surface and centrifugal potentials. The calculated half lives for proton decay from various Rhenium isotopes are then compared with the universal decay law (UDL) model[2] to assess the efficiency of the present formalism. Geiger-Nuttal plots of the probable decays are analysed and their respective slopes and intercepts are evaluated.

Alpha and cluster decay half-lives for Tungsten (W) isotopes in the range between 2p drip line and beta stability line are studied. The sensitivity of different Skyrme parametrizations in predicting the alpha-decay and probable cluster decay modes from W isotopes have been analysed. The half-lives are calculated using UDL. Predicted half-lives are compared with ELDM and also with available experimental values. The use of HO and THO basis do not produce much differences in the results. The study also revealed the role of neutron shell closure in cluster decay process.

Cluster radioactivity is a rare cold nuclear process which is intermediate between alpha decay and spontaneous fission. The present work is a theoretical investigation of the feasibility of alpha decay and cluster radioactivity from proton rich Osmium (Os) isotopes with mass number ranging from 162–190. Osmium forms a part of the transition region between highly deformed and spherical nuclei. Calculations have been done using unified fission model and Hartree–Fock–Bogoliubov (HFB) theory. We have chosen only those decays with half-lives falling in measurable range. Geiger–Nuttall plot has been successfully reproduced. The isotope which is most favorable to each decay mode has a magic daughter nucleus.

Based on the concept of cold valley in cold fission and fusion, we have investigated the cluster decay process in 248−254 Cf isotopes. In addition to alpha particle minima, other deep minima occur for S, Ar and Ca clusters. It is found that inclusion of proximity potential does not change the position of minima but minima become deeper. Taking Coulomb and proximity potential as interacting barrier for post-scission region, we computed half-lives and other characteristics for various clusters from these parents. Our study reveals that these parents are stable against light clusters and unstable against heavy clusters. Computed half-lives for alpha decay agree with experimental values within two orders of magnitude. The most probable clusters from these parents are predicted to be 46 Ar, 48,50 Ca which indicate the role of doubly or near doubly magic clusters in cluster radioactivity. Odd A clusters are found to be favorable for emission from odd A parents. Cluster decay model is extended to symmetric region and it is found that symmetric fission is also probable which stresses the role of doubly or near doubly magic 132 Sn nuclei. Geiger-Nuttal plots were studied for various clusters and are found to be linear with varying slopes and intercepts.

Because logic excludes that protons and neutrons have an outer layer to hold
quarks together, there must by definition be a structural relationship between the
quarks themselves to avoid jeopardizing the stability of the nucleus. To
substantiate this, it is necessary to move away from the beaten track in an attempt
to better understand the functioning of the nucleus and the atom as a whole.
The structure of the nucleus of the atom has been re-mapped and spatially
rearranged and, in its simplicity, explains completely the inner workings of that
atomic nucleus. It became immediately clear that it was only a small glimpse into
a whole new world that has remained hidden so far and undoubtedly will open
new fields of research in both physics and chemistry.

We present the first spectroscopic measurements of the [O iii] 5007 Å line in two z ∼ 3.1 Lymanalpha emitting galaxies (LAEs) using the new near-infrared instrument LUCIFER1 on the 8.4m Large Binocular Telescope (LBT). We also describe the optical imaging and spectroscopic observations used to identify these Ly-α emitting galaxies. Using the [O iii] line we have measured accurate systemic redshifts for these two galaxies, and discovered a velocity offset between the [O iii] and Ly-α lines in both, with the Ly-α line peaking 342 and 125 km s -1 redward of the systemic velocity. These velocity offsets imply that there are powerful outflows in high-redshift LAEs. They also ease the transmission of Ly-α photons through the interstellar medium and intergalactic medium around the galaxies. By measuring these offsets directly, we can refine both Ly-α-based tests for reionization, and Ly-α luminosity function measurements where the Ly-α forest affects the blue wing of the line. Our work also provides the first direct constraints on the strength of the [O iii] line in high-redshift LAEs. We find [O iii] fluxes of 7 and 36 ×10 -17 erg s -1 cm -2 in two z ∼ 3.1 LAEs. These lines are strong enough to dominate broad-band flux measurements that include the line (in this case, K s band photometry). Spectral energy distribution fits that do not account for the lines would therefore overestimate the 4000 Å (and/or Balmer) break strength in such galaxies, and hence also the ages and stellar masses of such high-z galaxies.

Using the CLEO II detector at the Cornell Electron Storage Ring we have measured the Ξ 0 c decay asymmetry parameter in the decay Ξ 0 c → Ξ − π +. We find α Ξ 0 c α Ξ = 0.26 ± 0.18(stat) +0.05 −0.04 (syst), using the world average value of α Ξ = −0.456 ± 0.014 we obtain α Ξ 0 c = −0.56 ± 0.39(stat) +0.10 −0.09 (syst). The physically allowed range of a decay asymmetry parameter is −1 < α < +1. Our result prefers a negative value: α Ξ 0 c is < 0.1 at the 90% CL. The central value occupies the middle of the theoretically expected range but is not yet precise enough to choose between models.

Self-irradiation can affect durability of glasses used to immobilize high-level nuclear waste (HLW). e stability of glasses can also be indirectly affected by the radiolytic changes in contact water leading to decrease in its pH although this is unlikely to occur for disposal systems where the interaction of groundwater with glass is delayed to times when radiation dose rates are decreased to levels insignificant to cause such effects. Besides, interaction of the water influenced by radiation with other repository protective elements (container and bentonite) will suppress the radiolytic changes. Literature analysis shows practical absence or very weak effect of self-irradiation on structure and characteristics of borosilicate glasses with typical content of nuclear waste. Data for aluminophosphate glass used in Russia have showed that, after c-irradiation with a dose of 6.2•10 7 Gy, the leaching rates of elements were decreased approximately twice relatively to pristine samples.

Alpha and cluster decay half-lives for Tungsten (W) isotopes in the range between 2p drip line and beta stability line are studied. The sensitivity of different Skyrme parametrizations in predicting the alpha-decay and probable cluster decay modes from W isotopes have been analysed. The half-lives are calculated using UDL. Predicted half-lives are compared with ELDM and also with available experimental values. The use of HO and THO basis do not produce much differences in the results. The study also revealed the role of neutron shell closure in cluster decay process.

Alpha and cluster decay half-lives for Tungsten (W) isotopes in the range between 2p drip line and beta stability line are studied. The sensitivity of different Skyrme parametrizations in predicting the alpha-decay and probable cluster decay modes from W isotopes have been analysed. The half-lives are calculated using UDL. Predicted half-lives are compared with ELDM and also with available experimental values. The use of HO and THO basis do not produce much differences in the results. The study also revealed the role of neutron shell closure in cluster decay process.

Cluster radioactivity is a rare cold nuclear process which is intermediate between alpha decay and spontaneous fission. The present work is a theoretical investigation of the feasibility of alpha decay and cluster radioactivity from proton rich Osmium (Os) isotopes with mass number ranging from 162–190. Osmium forms a part of the transition region between highly deformed and spherical nuclei. Calculations have been done using unified fission model and Hartree–Fock–Bogoliubov (HFB) theory. We have chosen only those decays with half-lives falling in measurable range. Geiger–Nuttall plot has been successfully reproduced. The isotope which is most favorable to each decay mode has a magic daughter nucleus.

The influence of the electron cloud on the α decay constant is estimated by using relativistic electron binding energies to be a few per mil with an uncertainty of about one per mil. A few nuclides are suggested for measuring this influence in a storage ring.

LBL-3409 The one-level R-matrix alpha decay rate theory has been extended to the : , ~ alpha decay of odd-odd nuclei by carrying out the more involved recoupling ,¥hd fractional parentage expansion. Graphical representations are employed to carry out the expansion which greatly simplifies the calculations. Relative alpha decay rates of ZlOAt were calculated asstuning shell-model wave functions

The unstable heavier nuclei release energy spontaneously by emitting radiations and particles, the process called radioactivity, namely, alpha, beta and gamma radioactive decays. In addition to these three types of decays, there exists fourth type of radioactivity known as cluster radioactivity (CR), defined as the spontaneous emission of fragments or clusters (A ≥ 4) heavier than alpha particle but less than a fission fragment. The decays of number of radioactive nuclei in trans-lead region, which lead to doubly magic Pb (Z=82, N=126) or neighboring daughter nuclei through emission of various clusters have been explored in many experimental as well as theoretical studies during last 3-4 decades. The shell closure in the atomic nucleus has now been established as the prominent cause of the process of CR.