States Of Daughter Nuclei Research Articles

Study of α-Decay Energy by an Artificial Neural Network Considering Pairing and Shell Effects

We build and train an artificial neural network (ANN) model based on experimental α-decay energy (Qα) data. In addition to decays between the ground states of parent and daughter nuclei, decays from the ground states of parent nuclei to the excited states of daughter nuclei are also included. In this way, the number of samples is increased dramatically. The α particle is assumed to have a spherical symmetric shape. The root-mean-square deviation between the calculated results obtained from the ANN model and the experimental data is 0.105 MeV. It shows a good predictive power for α-decay energy with the ANN model. The influence of different inputs is investigated. It is found that both the shell effect and the pairing effect result in an obvious improvement of the predictive power of the ANN model, and the shell effect plays a more important role. The optimal result can be obtained when both the shell and pairing effects are considered simultaneously. The application of the ANN model in predicting α-decay energy indicates a neutron magic number at N=184 in the superheavy nuclei mass region.

Search for evidence of rotational cluster bands in O18

Clustering in $^{18}\mathrm{O}$ is of great interest to the nuclear physics community, due to theoretical predictions of $\mathrm{core}+\ensuremath{\alpha}$ and nuclear molecular structures. An experiment was performed in order to measure branching ratios for states in $^{18}\mathrm{O}$, determining the tendency towards clustering based on the value of ${\mathrm{\ensuremath{\Gamma}}}_{\ensuremath{\alpha}}/{\mathrm{\ensuremath{\Gamma}}}_{\text{tot}}$ for each state, and the reduced widths compared to the Wigner limit. An experimental method that enables the measurement of branching ratios for almost all available decay modes, including $\ensuremath{\gamma}$ decay, $\ensuremath{\alpha}$ decay, and $n$ decay, was employed. The method is also sensitive to the population of excited states in daughter nuclei, allowing for more accurate determination of the ${\ensuremath{\alpha}}_{0}$ branch. The measurements represent, for several states, either the first branching ratio measurement or the first determination of ${\mathrm{\ensuremath{\Gamma}}}_{\ensuremath{\alpha}}/{\mathrm{\ensuremath{\Gamma}}}_{\text{tot}}$. Based on these measurements, no evidence of consistent cluster structure is seen across any of the bands previously proposed, casting doubt on their existence. Despite this, some states displaying cluster structure are observed.

Two-phonon structure of the neutron-rich nuclei

Starting from the Skyrme energy-density functional, the microscopic model of the spin-isospin excitations is developed for the β-delayed γ-spectroscopy. We take into account the coupling between one- and two-phonon terms in the wave functions of 1+ states of daughter nuclei. An extension of the two-phonon space allowing for the additional charge-exchange phonons substantially enriches the 1+ spectrum. As an example, the β-decay rates of neutron-rich nuclei 126,128Cd are discussed.

Effects of nuclear collective vibrations on the α -decay fine structure of vibrational nuclei with A≈220

The multichannel cluster model (MCCM) is generalized to investigate the effect of nuclear collective vibrations on the $\ensuremath{\alpha}$-decay fine structure. Vibrational excitations up to two-phonon states are taken into account and coupled-channels calculations are performed for vibrational Rn, Ra, Th, and U isotopes. Without introducing any additional adjustable parameter, the calculated $\ensuremath{\alpha}$-decay branching ratios to various vibrational states show good agreement with the experimental data. In particular, it is shown that the $\ensuremath{\alpha}$-decay fine structure is strongly correlated with vibrational excitations, offering an alternative tool to explore the phonon states in daughter nuclei. Despite the $N=126$ shell closure, the calculated $\ensuremath{\alpha}$-decay half-lives are also found to be in good agreement with the experimental data. A unified description of the $\ensuremath{\alpha}$-decay fine structure has been achieved by the MCCM for both rotational and vibrational nuclei.

Energy rates due to weak decay rates of vanadium isotopes in stellar environment

The neutrino cooling and gamma heating rates are considered as an important input needed to study the final phases of the evolution of high-mass stars. The weak-interaction mediated processes, namely the $\beta $-decay and electron capture, significantly change the lepton to baryon ratio and accelerate the contraction of the core. The emission of resulting neutrinos/antineutrinos tend to cool the stellar core. On the other hand gamma rays are produced because of electron capture and $\beta $-decay to excited states in daughter nuclei. These gamma rays heat the core and contribute to increase of entropy which may cause convection to occur. In the present work, the weak-interaction heating and cooling rates on a chain of twenty two isotopes of vanadium having mass in the range 43–64 have been estimated using the proton-neutron quasiparticle random phase approximation theory. The rates have been computed for the temperature ranging from ($10^{7}\mbox{--}3\times 10^{10}$) K and for the density range $(10\mbox{--}10^{11})~\mbox{g/cm}^{3}$. Our calculated neutrino energy loss rates have also been compared with the previously reported rates calculated using other theoretical models. At high stellar temperatures, our rates are larger by 1–2 orders of magnitude as compared to previous results.

Registration of Low-Intensity Alpha–Gamma Transitions in the Chain of 226Ra Decay

The results are presented from an experiment to measure the probabilities of γ-quanta emission from the first excited states of daughter nuclei formed in α-decay chain of the 226Ra nucleus. The use of fast temporal digitizers of the shape of the signal from a semiconductor α-detector and a germanium γ-detector of large volume allows the probabilities of the decay of the first excited states to be estimated at the level of 10–5 from the main mode of decay.

Using fast digital converters to detect bremsstrahlung radiation during the alpha decay of heavy nuclei

A large-volume germanium detector coupled with fast signal digitizers is proposed for use in experiments to study interference effects in yields of the bremsstrahlung radiation that accompanies alpha decays of heavy nuclei. When wavelet processing is applied to the signals from detectors, the time resolution can be as fine as ~30 ns for a detector with a volume of ≥100 cm3. This method is used to measure experimentally the probability of the emission of γ-quanta from excited states of daughter nuclei produced in the α-decay chain of 226Ra.

A highly efficient HPGE gamma-ray spectrometer for investigating ββ decay to excited states

A new low-background spectrometer based on a HPGe detector with a sensitive volume of 600 cm3 is developed to investigate rare nuclear processes such as resonance neutrinoless double electron capture and two-neutrino double beta decay to excited states of daughter nuclei. The spectrometer is installed at the Modane underground laboratory (France) at a depth of 4800 m w.e. The spectrometer background is measured and the spectrometer sensitivity is determined for measuring sources of double beta decay.

α-Decay half-lives, α-capture cross sections, and α-nucleous interaction

The expression for the α-nuclear potential was found. This potential describes the α-decay half-lives for the ground states of nuclei and the α-particle capture cross sections for 40Ca, 44Ca, 59Co, 208Pb, and 209Bi nuclei well. The potential was used to calculate the probabilities of α-transitions from the ground states of parent nuclei to different excited states of daughter nuclei. Simple analytical relations for calculating α-decay half-lives for transitions between the ground states of nuclei are determined.

New results for double-beta decay of 100Mo to excited final states of 100Ru using the TUNL-ITEP apparatus

The coincidence detection efficiency of the TUNL-ITEP apparatus designed for measuring half-life times of two-neutrino double-beta ( 2 ν β β ) decay transitions to excited final states in daughter nuclei has been measured with a factor of 2.4 improved accuracy. In addition, the previous measuring time of 455 days for the study of the 100Mo 2 ν β β decay to the first excited 0 1 + state in 100Ru has been increased by 450 days, and a new result (combined with the previous measurement obtained with the same apparatus) for this transition is presented: T 1 / 2 = [ 5.5 − 0.8 + 1.2 ( stat ) ± 0.3 ( syst ) ] × 10 20 yr . Measured 2 ν β β decay half-life times to excited states can be used to test the reliability of nuclear matrix element calculations needed for determining the effective neutrino mass from zero-neutrino double-beta decay data. We also present new limits for transitions to higher excited states in 100Ru which, if improved, may be of interest for more exotic conjectures, like a bosonic component to neutrino statistics.

Double-beta decay to the excited states (Experiment)

The brief review on the ββ decay to excited states of daughter nuclei is performed. New positive result of experiments with 100Mo for transition to 0+ excited state in 100Ru are presented.

Isospin Mixing in the Isobaric Analog State Derived from the (p,nIASp̃) Reaction on140Ce,172,174,176Yb, and208Pb

An exclusive coincidence experiment using the $({p,n}_{\mathrm{IAS}}\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{p})$ reaction on ${}^{140}\mathrm{Ce}$, ${}^{172,174,176}\mathrm{Yb}$, and ${}^{208}\mathrm{Pb}$ was carried out for the first time by measuring decay protons from the isobaric analog states (IAS). Spreading widths of the IAS are deduced from the escape and total widths. The results show a strong isospin dependence which can be explained by the isospin mixing effect due to the coupling to the ${T}_{0}$ component among three multiplets ${T\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}T}_{0}\ensuremath{-}1$, ${T}_{0}$, and ${T}_{0}+1$ of isovector monopole states in daughter nuclei. Empirical isospin mixing probabilities are found to be consistent with microscopic sum rule predictions.

QECMeasurement of124,125,127-130La

For neutron-deficient 124,125,127-130 La, Q EC measurement has been performed by determining β + -ray maximum energies. The radioactive sources were prepared by on-line mass-separation following the fusion-evaporation reactions 92, nat Mo( 36 Ar, 3 p x n ). The β + -rays were measured with an HPGe detector in β-γ coincidence mode in which γ-rays were detected with another HPGe detector for specifying an excited state in daughter nucleus. By unfolding the β + -ray spectra using experimental response functions, the Q EC -values of 124, 125, 127, 130 La were newly obtained, and those of 128, 129 La were improved in their accuracy. The Q EC -values obtained and the resulting atomic masses are compared with theoretical predictions. The results of half-life calculation and two-neutron separation energies using the experimental Q EC -values are also discussed.

Search for inclusive double beta decay of 150Nd to excited states of 150Sm at Laboratori Nazionali del Gran Sasso

Double beta decay to excited states of daughter nuclei is poorely studied (even if evidence for the decay has been recently reported). Measurements were performed at Laboratori Nazionali del Gran Sasso with a germanium detector, by searching for the de-excitation gamma rays of the daughter nuclides. New lower limits on the half-lives for double beta decay of 150 Nd to excited states of 150 Sm have been obtained. They range between 6×10 19 and 10×10 19 years (90% C.L.). A further measurement on 6 kg of natural Nd is in progress, preliminary results and a detailed study of intrinsic radioactivity of the sample are presented.