Recent developments in radioactive charged-particle emissions and related phenomena

Abstract

The advent and intensive use of new detector technologies as well as radioactive ion beam facilities have opened up possibilities to investigate alpha, proton and cluster decays of highly unstable nuclei. This article provides a review of the current status of our understanding of clustering and the corresponding radioactive particle decay process in atomic nuclei. We put alpha decay in the context of charged-particle emissions which also include one-and two-proton emissions as well as heavy cluster decay. The experimental as well as the theoretical advances achieved recently in these fields are presented. Emphasis is given to the recent discoveries of charged-particle decays from proton-rich nuclei around the proton drip line. Those decay measurements have shown to provide an important probe for studying the structure of the nuclei involved. Developments on the theoretical side in nuclear many-body theories and supercomputing facilities have also made substantial progress, enabling one to study the nuclear clusterization and decays within a microscopic and consistent framework. We report on properties induced by the nuclear interaction acting in the nuclear medium, like the pairing interaction, which have been uncovered by studying the microscopic structure of clusters. The competition between cluster formations as compared to the corresponding alpha-particle formation are included. In the review we also describe the search for super-heavy nuclei connected by chains of alpha and other radioactive particle decays.

Enhancement of α -particle formation near Sn100

“…There have been many subsequent efforts towards developing a quantitative description of α decay involving calculations of both the α-particle formation probability and the barrier penetrability (see, for example, Refs. [15][16][17] and references therein). There have even been recent attempts to calculate and compare the structure and α-particle formation of 212 Po and 104 Te using fully microscopic methods [18,19].…”

α-clustering in Heavy Nuclei 112–124Sn Probed with \((p,p\alpha )\) Reaction

“…Alpha decay has been known since the very early years of nuclear physics. It is generally described as the quantum tunneling of preformed α particles through the Coulomb barrier, which helps to understand the systematics of alpha decay half lives of heavy nuclei [1,2]. But such a naive picture of "preformed α particles" in the inner region of heavy nuclei is surely inconsistent with our knowledge of nuclear structure with nucleons moving in the nuclear mean field.…”

“…But such a naive picture of "preformed α particles" in the inner region of heavy nuclei is surely inconsistent with our knowledge of nuclear structure with nucleons moving in the nuclear mean field. In recent decades, it has been recognized that the dynamical α cluster can actually be accommodated in the low-density nuclear environment, which may potentially explain the origin of the α particles in the α decay process [2][3][4][5][6]. Although significant progress has been achieved in the cluster structure in light nuclei (e.g., [7][8][9][10][11][12][13][14]), there is so far no unambiguous experimental evidence reported for the existence of α clusters in heavy nuclei [2,15].…”

α-clustering at the Surface of Tin Isotopes 112−124Sn Studied with (p, pα) Reaction

“…Many novel cluster structures have been reported recently in light nuclei such as the molecular cluster structures in beryllium isotopes and the 3-α-linear-chain cluster states in carbon isotopes (e.g., [4][5][6][7][8][9][10][11]). On the other hand, there is so far no unambiguous experimental evidence reported for the existence of α clusters in heavy nuclei [12,13], despite its essential role in understanding the alpha decay process, which is generally described as the quantum tunneling of preformed alpha particles, a semi-classical picture initiated by George Gamow in 1920s [14]. Recent generalized relativistic density functional (gRDF) calculations, with cluster formation taken into account on the same footing as the nucleonic degree of freedom, suggest that α-clustering occurs at the low-density nuclear environment such as the surface of heavy nuclei, which could explain the origin of α particles in the α decay process [15,16].…”