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[en] The two very neutron-deficient isotopes of lead A=190, 192 have been produced and studied through the reaction ¹⁵⁶Gd-¹⁵⁴Gd(⁴⁰Ar,4nγ)¹⁹²Pb-¹⁹⁰Pb. The identification of those nuclei was also studied by means of the two additional reactions: ¹⁸²W(¹⁶O,6nγ)¹⁹²Pb and ¹⁵⁶Gd(⁴⁰Ar,6nγ)¹⁹⁰Pb. The pulsed ⁴⁰Ar beam available at ALICE (Orsay) enabled to record single γ spectra as well as four dimensional (energy-time) spectra corresponding to the correlation of two Ge(Li) detectors for different time windows. Tentative level-schemes are proposed. No significant deviation from the behavior previously reported for the heavier isotopes (ref.1) is pointed out. The data are consistently reproduced within a 2 q.p formalism using an S.D.I. residual interaction. However a slow decrease of the 2₁⁺ level energy is observed which could be an indication of a weakly increasing collective trend when the number of neutron holes increases. Those experimental conclusions fairly agree with the theoretical predictions by F.Dickman and K.Dietrich (ref.2). As a matter of fact, the authors predict a spherical shape for the ground states and find a secondary prolate minimum of the deformation potential at low energy. But the latter is not well developped for A>184 suggesting a spherical behavior for the heavier isotopes

[en] In reply to the preceding Comment, we wish to stress that lack of consistency between experiments of similar quality justifies our claim that further searches for a superdeformed band in ¹⁹²Pb with more powerful instruments are called for. We believe that the main results presented in the Comment support this conclusion

[en] This Comment examines the claim of a lack of evidence for a superdeformed band in ¹⁹²Pb. We reaffirm the existence in our data of the superdeformed band in ¹⁹²Pb

[en] The evolution of the dynamic moment of inertia as a function of rotational frequency for superdeformed (SD) bands in the mass 150 region is characterized by pronounced isotopic and isotonic variations. The ground-state band structure in even-even nuclei developed many phenomenological and theoretical approaches to understand the structure of nucleus and yrast excitation energies. The present work provides a new insight to understand the nuclear structure of the SD-1 and SD-2 band of ¹⁹⁴Hg and ¹⁹²Pb, ¹⁹⁴Pb nuclei

[en] The absolute α-decay width of light lead isotopes is calculated within a spherical BCS formalism. Clustering features induced by the nuclear interaction appear by considering a large configuration space. Good agreement with experimental data is obtained

[en] The α-decay rates of ¹⁸⁶,¹⁸⁸,¹⁹⁰,¹⁹²Pb have been reported to have an anomalous dependence on neutron number. Theoretical calculations do not reproduce this unusual behavior. To obtain more precise α-decay branching ratios, we reinvestigated the decay properties of ¹⁸⁸,¹⁹⁰,¹⁹²Pb. Our data result in α-decay reduced widths whose dependence on N is similar to that observed for other elements. (orig.)

[en] Alpha decay is a type of radioactive decay in which an unstable nucleus decays through the emission of an alpha particle. The phenomenon was discovered by Rutherford in 1899 and in 1928, on the basis of quantum tunneling George Gamow gave a theoretical explanation to alpha decay process. In the case of heavy and superheavy nuclei, alpha decay is identified as the most important decay mode as it can give information regarding the nuclear structure. In the present paper we have studied the behavior of the isotopes of Pb against alpha decay and have thus verified the role of neutron shell closure in these decays. Within the Coulomb and Proximity Potential Model (CPPM) proposed by Santhosh et al., we have calculated alpha decay half lives of Pb (Z = 82) isotopes in the region 178 ≤ A ≤ 220 for all the transitions with minimum angular momentum transfer

[en] Alpha-decay transitions between ground states of doubly-even nuclei are taken to represent unhindered decays. Reduced widths for these s-wave transitions behave in a regular fashion as a function of both neutron and atomic number. They are largest for nuclei two or four particles beyond a closed shell (with sharp minima at the shell) and they then decrease as the next closure is approached. The s-wave widths for ^186188190192Pb, however, have been reported to behave anomalously, i.e., they purportedly increase by a factor of 30 between ¹⁸⁶Pb (N = 104) and ¹⁹²Ob (N = 110) instead of decreasing as one nears N = 126. Theoretical calculations have not reproduced this unusual behavior. The [electron-capture (EC) + β⁺] strengths were deduced from K x-ray intensities. A number of corrections are involved in such determinations. We undertook the investigation of the (EC + β⁺) decay schemes of these neutron-deficient lead isotopes, in conjunction with studies of their α-decay properties, to obtain more reliable α-branching ratios. Herein we present new information on ¹⁸⁶Pb and discuss the partial α half-lives for ¹⁹²Pb, ¹⁹⁰Pb, ¹⁸⁸Pb, and ¹⁸⁶Pb together with α-decay rates for even-even nuclei with Z greater than or equal to 78

[en] Full text: A recently developed two-level mixing model of the transition from superdeformed to normal-deformed nuclear shape is applied to evaluate the tunnelling width of the decay-out process in ¹⁹²Pb, ¹⁹⁴Pb and ¹⁹⁶Pb. We estimate the level densities and gamma-decay widths for the normally-deformed states at the excitation energy of the decay, and use observed properties of the superdeformed states as input for the model. The relationship between the extracted widths and the potential barrier between the shapes is discussed. Copyright (2005) Australian Institute of Physics