Alpha-particle and triton cluster states in 19F

We calculate the energies and other properties of three- and four-particle cluster states in the nuclei ¹⁹F and ¹⁹Ne, treated as eigenstat es of a local cluster-core potential. The potential we consider is a symmetrized Saxon-Woods well which has the advantage that a single value of the potential depth can generate rotational spectra of levels with different values of orbital angular momentum L; in this respect, it is very similar to the folding potentials which have been used in previous cluster calculations. We discuss the cluster states in the light of recent three- and four-particle heavy ion transfer reactions and studies of the electromagnetic decay properties of bound and continuum states. Most of the states observed to be strongly populated in the transfer experiments can be unambiguously assigned to cluster bands based on ¹⁶O + t and ¹⁵N + α configurations with various angular momenta and node numbers. Some evidence for mixing between triton and alpha configurations exists and is discussed. We also calculate the electromagnetic properties of the cluster states and find that, with few exceptions, they are in good agreement with the experimental data. Some El transitions are predicted to be very large, contrary to existing experiments, and new experiments are proposed to investigate this discrepancy.     

Helium-cluster decay widths of molecular states in beryllium and carbon isotopes

⁴He (i.e., α particle) and ⁶He emissions from possible molecular states in beryllium and carbon isotopes have been investigated using a mean-field-type cluster potential. Calculations can reasonably describe the α-decay widths of studied states in beryllium and carbon isotopes, and also ²⁰Ne, compared with experiments. For the nucleus ¹⁰Be, we discussed α-decay widths with different shapes or different decay modes, in order to understand the very different decay widths of two excited states. The widths of ⁶He decays from ¹²Be and α decays from ^13,14C are predicted, which could be useful for future experiments.     

Alpha-particle states in extended Elliott model

A model of α-particle and quasimolecular states of nuclei based on the microscopic Hamiltonian of broken SU(3) symmetry commutative with the antisymmetrizer is built. The model provides an explanation for all qualitative properties of the spectra and allows one to calculate the spectroscopic factors.     

Alpha-particle unstable states in12C

Alpha particle unstable states in¹²C have been investigated using the three reactions¹⁴N(d, α′)¹²C,¹⁴N(d, α′α)⁸Be and¹²C(α, α′)¹²C. Excitation cross sections and angular distributions have been measured for the reactions¹⁴N(d, α′) at 52 MeV and¹²C(α, α′) at 90 MeV. For a few angle pairs the α-decay of excited states in¹²C have been observed in a¹⁴N(d, α′α) correlation measurement. The reactions selectively excite onlyT=0 states. A previously undetected level with a large α-decay width (Γ=1.2 MeV) has been observed at 15.62 MeV excitation. This level shows up clearly in both reactions and is further distinguished from the nearby 14.08 state in the correlation measurement because of the distinctly different energy distributions of the decay products. On the basis of a particle angular distributions the 15.62 MeV level was assigned spin and parity 4⁺ and the level at 14.08 was assigned 3^?. The latter differs from the value suggest by earlier work. Comparison with DWBA calculations indicates that angular distributions of all other prominent levels are in agreement with their earlier assignments. Two levels at 19.20 and 20.30 MeV (both Γ?0.4 MeV) and three further levels at 21.81, 22.7 and 24.24 MeV also decay predominantly by α-emission.     

Channel-coupling contribution to the widths of decay nuclear states and to their wave functions

By using the formalism of the quantum theory of fission, the amplitudes of partial decay widths and the asymptotic behavior of the wave function for a decaying nucleus are found with allowance for open-decay-channel coupling not only for fission, but also for the binary decays of nuclei through protonic, alphaparticle, cluster, and other channels.     

Charmonium decay widths in magnetized matter

The European Physical Journal A - In this paper, we investigated the spectroscopy of heavy tetraquarks through a relativistic diquark-antidiquark model. To this aim, the two-bosonic Klein-Gordon...     

Mechanisms and widths of two-proton decay

A method for calculating the widths of two-proton decay of nuclei with regard to its deep subbarrier character is proposed. The structure and coupling of the channels of facilitated two-proton decay of spherical nuclei are considered for the diproton and uncorrelated mechanisms of two-proton decay.     

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.

     

Mass spectra and leptonic decay widths of heavy quarkonia

A nonrelativistic Hamiltonian with plausible spin dependent corrections is proposed for the quarkonia below their respective strong decay thresholds. With only six free parameters this model reproduces the nine known masses of the bottomonia within about 1 MeV, the six known masses of the charmonia within a few MeV and the five known leptonic decay widths of the states within about 20%. The model is then used to predict the masses of the remaining 43 qu arkonia (some of them for the first time) and of the leptonic decay widths of the two states. Comparison with some other models is made. Received: 17 June 1997     

Alpha-particle decays from excited states in ~(24)Mg

Using a cluster model based on the Woods-Saxon potential, alpha-particle decays from excited states in 24Mg have been system atically 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 ...     

Axial couplings and strong decay widths of heavy hadrons

We calculate the axial couplings of mesons and baryons containing a heavy quark in the static limit using lattice QCD. These couplings determine the leading interactions in heavy hadron chiral perturbation theory and are central quantities in heavy quark physics, as they control strong decay widths and the light quark mass dependence of heavy hadron observables. Our analysis makes use of lattice data at six different pion masses, 227 MeV相似文献   

First measurement of the partial widths of 209Bi decay to the ground and to the first excited states

209Bi alpha decay to the ground and to the first excited state have been recently observed for the first time with a large BGO scintillating bolometer. The half-life of 209Bi is determined to be τ(1/2)=(2.01±0.08)×10(19) yr while the branching ratio for the ground-state to ground-state transition is (98.8±0.3)%.     

Influence of N cluster states on band dispersion in GaInNAs quantum wells

We use a modified band-anticrossing (BAC) model to investigate the band dispersion in a GaN_xAs_1-x/AlGaAs quantum well (QW) as a function of hydrostatic pressure. The band edge mass increases considerably more quickly with pressure than in the case of a GaAs/AlGaAs QW, and the subband separation also decreases significantly. We predict that the strong anticrossing interaction between the GaAs host conduction band and isolated N levels will inhibit tunnelling through the QW for a range of energy above the isolated N levels. The energy of N resonant states depends strongly on details of the local environment, giving a broader calculated distribution of N states in GaInNAs compared to GaNAs.     

Alpha decay and cluster decay of some neutron-rich actinide nuclei

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.     

Partial decay widths of baryons in the spin-momentum operator expansion method

The cross-sections for photo- and pion-induced production of baryon resonances and their partial decay widths to the two-body and multi-body final states are calculated in the framework of the operator expansion method. The approach is fully relativistic invariant, and it allows us to perform combined analyses of different reactions imposing directly the analyticity and unitarity constraints. All formulae are given explicitly in the form used by the Crystal Barrel Collaboration in the partial-wave analysis.