[en] Octupole deformations are studied for the usually neglected components of the octupole tensor {Y_λ=3,μ≠0} in nuclei around ²¹⁸Ra by using the Strutinsky microscopic-macroscopic method. (author)

[en] The alpha Hindrance Factors (HFs) which is the ratio of experimentally observed partial half-life to the calculated partial half-life is an important parameter which quantifies the overlap of nuclear wave functions of the initial state of parent and final state of daughter nuclei. In this study, we calculates HFs of 182 even-even alpha emitters using ALPHAD program based on Preston's equations and presents the HFs systematics of 1-, 3-, 2+, 4+ and 6+ states with neutron number. In Figure 1, we present the variation of HFs of 1- and 3- states observed in ^218-226Ra isotopes with neutron number. From this figure it is clear that, the HFs of both 1-and 3-states decrease with reduction in neutron number. This decrease of HFs is attributed to onset of intrinsic reflection asymmetry, but there is a trend reversal at N=132 (²¹⁸Ra), which might be a possible indication of departure from static octupole deformation. Similar HFs systematics is studied in Rn, Th, U and Pu isotopes. (author)

[en] Heavy nuclei with Z≥82 are generally less accessible for detailed studies with usual nuclear spectroscopy methods. Therefore the study of half lives via α-decay and/or cluster decay represents one of the main tools for the nuclear structures as well as spectroscopy of ground and excited states of a nuclei in the mass region A=220. Again, the mass region of A ∼ 220 is crucial because there is strong specific evidence that in certain heavy and/or super-heavy regions, octupole-deformed atomic nuclei are distorted into a pear shape. The major purpose of the present study is to examine the α and cluster decay processes in the region of A ∼ 220 of Ra isotopes to predict the existence of spherical shell/sub-shell closures in the daughter lead region within an axially deformed relativistic mean field (RMF) theory with NL3 force parameter set

[en] The states of ground and K^π=0^- bands are obtained though projection from an 'intrinsic' quadrupole and octupole-deformed ground state with non-definite reflection parity. An effective Hamiltonian and E1 transition operator are defined in terms of quadrupole and octupole bosons. Applications to ^218,220,226Ra show a very good agreement with available data. Finally the formalism is extended to another three pairs of positive-negative parity bands: (β, 0^-), (γ, 2^-), (1⁺, 1^-). The members of the last doublet are of magnetic and electric nature, respectively. (author). Letter-to-the-editor

[en] In present work, we have calculated the hindrance factors of 182 even-even alpha emitters using Preston’s formulation of alpha decay probabilities and presented HFs systematics of 1^- and 3^- states in reflection asymmetric even-even quadruple-octupole deformed nuclides (A~216-230). The calculated HFs of both 1^- and 3^- states decrease with reduction in neutron number and this decrease is attributed to onset of intrinsic reflection asymmetry. There is a trend reversal for 1^- states at N=132 (²¹⁸Ra) and N=134 (²²⁰Rn), which might be a possible indication of departure from static octupole deformation. Similarly, HFs systematics is discussed for ^224-230Th and ^232-236U isotopic chains along with 2⁺ states observed in daughter nuclei in N=132-146 isotonic chains. (author)

[en] Analysis of the second differences of the level energies, Δ²E_rot(I), for the negative-parity bands with only odd spins in ^236,238U, ²¹⁸Ra, and ¹⁵⁶Er shows, at least for I> or =7, a ΔI = 4 alternating energy-shift term. Such an unusual signature term is not expected in the framework of the quadrupole deformation model

[en] The interacting multiboson model (IMBM) introduced earlier, in its spdf boson case, is applied to a new experiment on the vibrational nucleus ₈₈²¹⁸Ra₁₃₀. It is shown to describe in a natural way, with the essential participation of pf bosons, both the ground yrast bands with positive and negative parity, and the peculiar side yrare bands with the same space π and opposite spin (-)^I parity. So this experiment together with its boson interpretation can be viewed as evidence for the existence of combined dipole-octupole correlations in nuclei. (author)

[en] The energy spectrum and deexcitation pattern of ²¹⁸Ra cannot be explained within the interacting boson approximation unless g bosons are included. This is done by restricting the basis to fully aligned states. The framework developed is applicable to any situation in which a vibrational pattern prevails

[en] The interacting multi boson model (IMBM) introduced earlier, in its spdf boson case, is applied to a new experiment on the vibrational nucleus ²¹⁸₈₈Ra₁₃₀. It is shown to describe in a ntural way, with the essential participation of pf bosons, both the ground yrast bands with positive and negative parity, and the peculiar side yrare bands with the same space π and opposite spin (-(¹ parity. So this experiment together with its boson interpretation can be viewed as evidence for the existence of combined dipole octupole correlations in nuclei

[en] The high spin states of ²¹⁸Ra exhibit a band of alternating parity states with enhanced E1 decay mode (B(E1) >=10^-2 W.u.). Various theoretical models are discussed, such as the octupole model, f and g boson model, second order E1 operator in IBA1 model, and the cluster model. The enhanced E1 deexcitation favors the cluster model. The low spin negative parity states lie on a J(J+1) trajectory contrary to the assumed vibrational character of the negative parity states in ²¹⁸Ra. A change in the character of states above the 11^- state is observed via a change in the moment of inertia and a decrease in the B(E1)/B(E2) branch ratios. Two quasi-particle 11^- states systematically occurring in the Ra-isotopes may be responsible for this change. The well known effect of loss of collectivity arising from two quasi-particle states, as observed in the hindrance of B(E2), is suggested to more dramatically hinder the B(E1) and lead to a reduction in the branch ratio B(E1)/B(E2). This observation suggests that the E1 enhancement is of collective character