Fine structure of α decay in odd nuclei (original) (raw)
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Systematics of the α-decay to rotational states
Physical Review C, 2006
We analyze α decays to rotational states in even-even nuclei by using the stationary coupled channels approach. Collective excitations are described by the rigid rotator model. The α-nucleus interaction is given by a double folding procedure using M3Y plus Coulomb nucleon-nucleon forces. We use a harmonic oscillator repulsive potential with one independent parameter, to simulate the Pauli principle. The decaying state is identified with the first resonance inside the resulting pocketlike potential. The energy of the resonant state is adjusted to the experimental Q value by using the depth of the repulsion. We obtained a good agreement with existing experimental data concerning total half-lives and decay widths to J = 2 + states by changing the factor multiplying the nucleon-nucleon interaction according to the rule v a = 0.668 − 0.004 (A − 208). Concerning the decay widths to J = 4 + states we obtained a good agreement for Z = 90 neutron chain and a satisfactory description for Z = 92, 96, and 98, chains. It is possible to improve the agreement concerning transitions to J = 4 + states by considering a constant quenching strength v a = 0.6 and by changing the width of the Gaussian describing the α-cluster density according to the rule b = 1.744 − 0.032 (A − 208). We found out that the computed widths to excited states are correlated with the corresponding deformation parameters. We conclude that the α-decay fine structure is a sensitive tool to probe fundamental aspects of the effective nuclear interaction and its dependence on the α clustering.
Folding description of the fine structure of α decay to2+vibrational and transitional states
Physical Review C, 2007
We analyze α-decays to ground and 2 + vibrational states in even-even nuclei by using a coupled channels formalism. The α-nucleus interaction is simulated by a double folding procedure using M3Y plus Coulomb two-body forces. Collective excitations are described by vibrations of the nuclear surface. We use a repulsive potential, with one independent parameter, in order to simulate Pauli principle and to adjust the energy of the resonant state to the experimental Q-value. The decaying state is identified with the zero nodes resonance inside the resulting pocket-like potential. We have found that the fine structure is very sensitive to the strength of the repulsive core and the vibrational parameter of the α-nucleus potential. A satisfactory agreement with existing experimental data was obtained by using the vibrational strength as a free parameter. It turns out that the inverse of this parameter is proportional to the logarithm of the hindrance factor squared. Based on this fact we have made predictions for 15 vibrational α-emitters.
Systematics of the α decay to vibrational2+states
Physical Review C, 2005
We give a systematic analysis of α decays to low-lying 2 + states in even-even nuclei. Collective excitations are considered within the spherical quasiparticle random-phase approximation. We use realistic G-matrix elements of the Bonn interaction as a residual two-body force. The only free parameters are the ratio between the isovector and isoscalar strengths and proton-neutron asymmetry. The formalism can reproduce the main experimental trends versus the excitation energy for both the B(E2) values and the α-decay hindrance factors. We reproduced most of the available data by using one common parametrization. It turns out that the fine structure of the α decay is more sensitive than electromagnetic transitions as a tool for investigating nuclear interaction. With the adopted parametrization, we predict B(E2) values and α-decay hindrance factors in even-even nuclei.
Systematization of α -decaying nuclei based on shell structures: The case of odd - Even and odd - Odd nuclei, 2017
In previous studies, we provided a novel systematization of α-decaying even-even and even-odd nuclei starting with the classically adopted mechanism [T. Yarman et al., Eur. Phys. J. A 52 (2016) 140; Eur. Phys. J. A 53 (2017) 4]. Knowing beforehand the measured decay half-life, we had taken as a parameter the probability of the α-particle as being first born in a unit period of time, within the parent nucleus before it is emitted out. We thence developed a scaffold based on shell properties of families composed of "alike nuclei". Along the same line, we now present a systematization of odd-even (OE) as well as odd-odd (OO) nuclei. We apply our approach further to the investigation of the effect of pairing (e.g., the effect when the number of nucleons is increased by one neutron), and that of unpairing (e.g., the effect when the number of nucleons is decreased by one neutron); thus it becomes an even number for the case of odd-even nuclei (Case OE), and an odd number in the case of odd-odd nuclei (Case OO). For the first case (OE), we pick the exemplar set 161Re, 217Fr, 243Bk, 263Db; where we delineate by, respectively, Re, Fr, Bk, and Db all of the odd-even or odd-odd isotopes that neighbor the four mentioned odd-even isotopes on the proposed scaffold. We proceed in the same way for the second case (OO). Thus, we choose the exemplar set of odd-odd nuclei 172Ir, 218Ac, 244Es. We then gather all of the Ir, Ac, and Es odd-odd and odd-even isotopes that neighbor the three mentioned odd-odd isotopes on the proposed scaffold. We show that, in the former case, pairing, as expected, generally increases stability of the given nucleus; and in the latter case, unpairing works in just the opposite direction - i.e., it generally increases instability. We disclose "stability peaks" versus Z for both sets of nuclei, we tackle here. Furthermore, we present a study to highlight an outlook of "odd-A nuclei" at hand. Contrary to the general expectation, we unveil no systematic on that.
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.
Fine structure of alpha decay for odd-oven isotopes of Am, Es, and Md nuclei
2016
Half lives of alpha decay for odd-even isotopes of Am 231-245 , Es 239-257 and Md 245261 nuclei from ground state to ground and excited states of daughter nuclei have been calculated using CYE model. In this work we take into account of both quadruple (β2) and hexadecapole (β4) deformations, as well as the spinparity of parent and daughter nuclei. The calculated half-lives are compared with available data and are found to be good agreement with each other. The Hindrance factor and branching ratios to the excited states of daughter nucleus also determined. The influence of alpha decay energy and the angular momentum of alpha particle on the half-life time calculation have been studied. The standard deviation value for half-life is computed.
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.
Anisotropy in alpha decay of odd-mass deformed nuclei
Physical Review C, 1992
Angular distributions and the corresponding absolute a decay widths are calculated microscopically in odd axially deformed nuclei. It is found that the angular distributions are mainly determined by the deformation. The available experimental data are well reproduced.
Systematization of α-decaying nuclei based on shell structures: The case of even-odd nuclei Systematization of α-decaying nuclei based on shell structures: The case of even-odd nuclei, 2017
Previously, we provided a novel systematization of α-decaying even-even nuclei starting with the classically adopted mechanism (Yarman et al., Eur. Phys. J. A52, 140 (2016)). The decay half-life of an α-decaying nucleus was framed so that i) the α-particle is taken at the outset to be born inside the parent nucleus with a given probability, ii) where it then keeps on bouncing off of the barrier of the parent nucleus till iii) it finally tunnels through the barrier. Knowing beforehand the measured decay half-life, we have taken into consideration, as a parameter, the probability of the α-particle being first born within the parent before it is emitted. We thence developed a scaffold based on shell properties of families composed of alike even-even nuclei. Nevertheless, our model allows us to incorporate any α-decaying nuclei, and along this line, we present a follow-up systematization of even-odd nuclei, with cases of odd-even and odd-odd α-decaying nuclei pending to be considered in a separate contribution. Notwithstanding, we make an effort herein to expand our approach to investigate the effect of "pairing" (e.g., when a number of nucleons in the given nucleus becomes an even number, instead of the initial odd number, due to the addition of at least one neutron). Our results show that "pairing", as expected, definitely increases the stability of the given nucleus.
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.