Α Decay as a Probe for Phase Transitions in Nuclei (original) (raw)

Alpha decay as a probe for the structure of neutron-deficient nuclei

The advent of radioactive ion beam facilities and new detector technologies have opened up new possibilities to investigate the radioactive decays of highly unstable nuclei, in particular the proton emission, α decay and heavy cluster decays from neutron-deficient (or proton-rich) nuclei around the proton drip line. It turns out that these decay measurements can serve as a unique probe for studying the structure of the nuclei involved. On the theoretical side, the development in nuclear many-body theories and supercomputing facilities have also made it possible to simulate the nuclear clusterization and decays from a microscopic and consistent perspective. In this article we would like to review the current status of these structure and decay studies in heavy nuclei, regarding both experimental and theoretical opportunities. We then discuss in detail the recent progress in our understanding of the nuclear α formation probabilities in heavy nuclei and their indication on the underlying nuclear structure.

Microscopic description of the anisotropy in alpha decay

Physical Review C, 1994

A microscopic description of alpha decay of odd mass nuclei is given for axially deformed nuclei. Realistic mean field+pairing residual interaction in a very large single particle basis is used. Systematics for At and Rn isotopes, as well as for Fr, are given. A pronounced anisotropic emission of alpha particles at low temperatures is predicted as function of deformation for the At and Rn isotopes. This shows that alpha decay is an excellent tool to probe intrinsic deformations in nuclei.

Microscopic description of the α-decay fine structure in spherical nuclei

Physical Review C, 2001

We give a systematic microscopic description of the ␣ decay to excited states in spherical nuclei. Low-lying collective excitations are considered within the quasiparticle random phase approximation. As a residual force we use the surface delta interaction. It turns out that this simple approach is able to reproduce the available experimental hindrance factors for transitions to 2 ϩ states in Po isotopes. We predict a linear dependence between the logarithm of the hindrance factor and the excitation energy of the 2 ϩ state.

Α-Decay Spectroscopy of Deformed Nuclei Reexamined

Physical Review C, 2008

We perform an extensive analysis of α-decays to 2 + and 4 + states in deformed even-even nuclei by using the stationary coupled channels approach. Collective excitations are described within the rigid rotor model. The α-nucleus interaction is given by a double folding procedure with M3Y plus Coulomb nucleon-nucleon forces. We use a repulsive potential with one independent parameter in order to localize the α-particle on the nuclear surface and to fit the experimental Q-value. The decaying state is identified with the first resonance inside the resulting pocket-like potential, as suggested by microscopic calculations. We obtain a good agreement with existing experimental data concerning decay widths to J = 2 + , 4 + states. The total α-decay half-lives agrees very well with experimental values by fitting the spectroscopic factor in terms of charge and neutron numbers separately for Z < 82 and Z > 82. We give predictions for intensities and hindrance factors for 52 even-even α-emitters with β 2 > 0.15 and E 2 + < 200 kev. Comparison between the phenomenological and microscopic spectroscopic factors revealed large α-clustering components for nuclei close and above N = 82, Z = 82, N = 126 magic numbers.

Nuclear field theory approach to alpha-decay

Physics Letters B, 1979

The nuclear field theory is applied to the calculation of relative c~-decay rates in 212 At. All possible configurations are considered. The importance of collective states is discussed.

Alpha decay from deformed nuclei

Nuclear Physics A, 1987

The reaction-theoretical formulation of (Y decay theory is extended to deformed nuclei in a particle-plus-rotor model and adapted for the use of harmonic oscillator functions. For testing purposes the formalism is applied to the decay of nuclides with reasonably well-established ground state shapes (spherical as well as deformed).

The investigation of 0+ ↔ 0− β decay in some spherical nuclei

Pramana, 2010

The 0 + ↔ 0 − first-forbidden β decay transitions have been investigated for some spherical nuclei. The theoretical framework is based on a proton-neutron quasiparticle random phase approximation (pnQRPA). The Woods-Saxon potential basis has been used in our calculations. The transition probabilities have been calculated within the ξ approximation. The relativistic β moment matrix element has been calculated both directly without any assumption and assuming that it is proportional to the non-relativistic one.

Beta Decay of Exotic Nuclei

Lecture Notes in Physics, 2000

In this chapter β-decay is discussed as a tool for studying the structure of atomic nuclei. An attempt is made to give a simple account of the topic so that the student can understand what they find in the literature about β-decay. The quantities of spectroscopic interest are defined and the student is shown how they can be derived from experiments. In the study of exotic nuclei often the first thing we learn about a nucleus is how it β-decays. A series of examples of β-decay studies of exotic nuclei is presented with the aim of both illustrating the most up-to-date techniques and showing the student the breadth of physics that can be addressed

Single universal curve for α decay derived from semi-microscopic calculations

A universal curve is one of the simple ways to get preliminary information about the α-decay half-life times of heavy nuclei. We try to find parametrization for the universal curve of α decay based on semi-microscopic calculations starting from the realistic Michigan-three-Yukawa Reid nucleon-nucleon interaction. Within the deformed density-dependent cluster model, the penetration probability and the assault frequency are calculated using the Wentzel-Kramers-Brillouin approximation. The deformations of daughter nuclei and the ground-state spin and parity of the involved nuclei are considered. For all studied decays, we found that it is accurate enough to express the assault frequency either as a function of the mass number of the parent nuclei or as a constant average value. The average preformation probability of the α cluster inside four groups of 166 even-(Z)-even (N), 117 odd-even, 141 even-odd, and 72 odd-odd α emitters is obtained, individually. The effects of participating unpaired nucleons in the involved nuclei as well as the influence of any differences in their ground-state spin and/or parity appear in the obtained average values of the preformation probability. We suggested a single universal curve for α decay with only one parameter. This parameter varies according to the classified four groups. It includes the preformation probability and the average assault frequency in addition to the pairing contribution.

Beta-decay studies for applied and basic nuclear physics

The European Physical Journal A

In this review we will present the results of recent \beta β−decaystudiesusingthetotalabsorptiontechniquethatcovertopicsofinterestforapplications,nuclearstructureandastrophysics.Thedecaysstudiedwereselectedprimarilybecausetheyhavealargeimpactonthepredictionof(a)thedecayheatinreactors,importantforthesafetyofpresentandfuturereactorsand(b)thereactorelectronanti−neutrinospectrum,ofinterestforparticle/nuclearphysicsandreactormonitoring.Forthesestudiesthetotalabsorptiontechniquewaschosen,sinceitistheonlymethodthatallowsonetoobtainβ -decay studies using the total absorption technique that cover topics of interest for applications, nuclear structure and astrophysics. The decays studied were selected primarily because they have a large impact on the prediction of (a) the decay heat in reactors, important for the safety of present and future reactors and (b) the reactor electron anti-neutrino spectrum, of interest for particle/nuclear physics and reactor monitoring. For these studies the total absorption technique was chosen, since it is the only method that allows one to obtainβdecaystudiesusingthetotalabsorptiontechniquethatcovertopicsofinterestforapplications,nuclearstructureandastrophysics.Thedecaysstudiedwereselectedprimarilybecausetheyhavealargeimpactonthepredictionof(a)thedecayheatinreactors,importantforthesafetyofpresentandfuturereactorsand(b)thereactorelectronantineutrinospectrum,ofinterestforparticle/nuclearphysicsandreactormonitoring.Forthesestudiesthetotalabsorptiontechniquewaschosen,sinceitistheonlymethodthatallowsonetoobtain\beta β−decayprobabilitiesfreefromasystematicerrorcalledthePandemoniumeffect.Thetotalabsorptiontechniqueisbasedonthedetectionoftheβ -decay probabilities free from a systematic error called the Pandemonium effect. The total absorption technique is based on the detection of theβdecayprobabilitiesfreefromasystematicerrorcalledthePandemoniumeffect.Thetotalabsorptiontechniqueisbasedonthedetectionofthe\gamma γcascadesthatfollowtheinitialγ cascades that follow the initialγcascadesthatfollowtheinitial\beta βdecay.Forthisreasonthetechniquerequirestheuseofcalorimeterswithveryhighβ decay. For this reason the technique requires the use of calorimeters with very highβdecay.Forthisreasonthetechniquerequirestheuseofcalorimeterswithveryhigh\gamma γ detection efficiency. The measurements presented and discuss...