The 2p radioactivity half-lives have been calculated within a tunneling process through the poten... more The 2p radioactivity half-lives have been calculated within a tunneling process through the potential barrier determined from the original version of the generalized liquid drop model and quasimolecular shapes. The sparse experimental data on the 2p radioactivity half-lives of the 12 O, 16 Ne, 19 Mg, 45 Fe, 48 Ni, 54 Zn, and 67 Kr nuclei are roughly reproduced when taking into account the Q exp 2p value. An analytic formula is provided to obtain rapidly these different half-lives. Using the Q 2p values extracted from the recent Nubase2020 table, extrapolations to other perhaps possible 2p emitters are proposed. Within the same approach, formulas to determine the 9 Be, 6,7 Li, 3,6 He, and 2,3 H decay half-lives at low excitation energy are also provided.
The alpha decay, the cluster radioactivity and the heavy particle emission half-lives of known an... more The alpha decay, the cluster radioactivity and the heavy particle emission half-lives of known and some still unknown superheavy nuclei have been investigated within the original Generalized Liquid Drop Model and analytic formulas. The Q value has been calculated mainly from the recent NUBASE2020 tables. The agreement between the experimental data and the theoretical predictions of the alpha decay half-lives of the superheavy nuclei is correct and some predictions are provided for unknown nuclei. For some emissions of heavy particles by superheavy nuclei the half-life is comparable to the alpha decay half-lives or even smaller.
Different Liquid Drop Model mass formulae have been studied. They include a Coulomb diffuseness c... more Different Liquid Drop Model mass formulae have been studied. They include a Coulomb diffuseness correction Z 2 /A term and pairing and shell energies of the Thomas-Fermi model. The influence of the selected charge radius, the curvature energy and different forms of the Wigner term has been investigated. Their coefficients have been determined by a least square fitting procedure to 2027 experimental atomic masses. The different fits lead to a surface energy coefficient of 17-18 MeV. A large equivalent rms radius (r0 = 1.22 − 1.24 fm) or a shorter central radius may be used. A rms deviation of 0.54 MeV can be reached between the experimental and theoretical masses. The remaining differences come from the determination of the shell and pairing energies. Mass predictions are given for exotic nuclei.
The efficiency of different mass formulas derived from the liquid drop model including or not the... more The efficiency of different mass formulas derived from the liquid drop model including or not the curvature energy, the Wigner term and different powers of the relative neutron excess I has been determined by a least square fitting procedure to the experimental atomic masses assuming a constant R0;charge/A 1= 3 ratio. The Wigner term and the curvature energy can be used independently to improve the accuracy of the mass formula. The different fits lead to a surface energy coefficient of around 17-18 MeV, a r sharp charge radius r0 of 1.22-1.23 fm and a proton form-factor correction to the Coulomb energy of around 0.9 MeV.
Within the preformed cluster model approach, the values of the preformation factors have been ded... more Within the preformed cluster model approach, the values of the preformation factors have been deduced from the experimental cluster decay half-lives assuming that the decay constant of the heavy-ion emission is the product of the assault frequency, the preformation factor and the penetrability. The law according to which the preformation factors follow a simple dependence on the mass of the cluster was confirmed. Then predictions for some most possible cluster decays are provided.
The occurence of "exotic" shapes in light N=Z α-like nuclei is investigated for 24 Mg+ 12 C and 3... more The occurence of "exotic" shapes in light N=Z α-like nuclei is investigated for 24 Mg+ 12 C and 32 S+ 24 Mg. Various approaches of superdeformed and hyperdeformed bands associated with quasimolecular resonant structures with low spin are presented. For both reactions, exclusive data were collected with the Binary Reaction Spectrometer in coincidence with EUROBALL IV installed at the VIVITRON Tandem facility of Strasbourg. Specific structures with large deformation were selectively populated in binary reactions and their associated γ-decays studied. The analysis of the binary and ternary reaction channels is discussed.
Longitudinal ternary and binary fission barriers of 36 Ar, 56 Ni and 252 Cf nuclei have been dete... more Longitudinal ternary and binary fission barriers of 36 Ar, 56 Ni and 252 Cf nuclei have been determined within a rotational liquid drop model taking into account the nuclear proximity energy. For the light nuclei the heights of the ternary fission barriers become competitive with the binary ones at high angular momenta since the maximum lies at an outer position and has a much higher moment of inertia.
The energy of actinide nuclei has been determined within a generalized liquid drop model taking i... more The energy of actinide nuclei has been determined within a generalized liquid drop model taking into account the proximity energy, the mass and charge asymmetry, an accurate nuclear radius in adding the shell and pairing energies. Double and triple-humped potential barriers appear. The second maximum corresponds to the transition from compact and creviced one-body shapes to two touching ellipsoids. A third minimum and third peak appear in special asymmetric exit channels where one fragment is almost a magic nucleus with a quasi-spherical shape while the other one evolves from oblate to prolate shapes. The heights of the double and triple-humped fission barriers agree precisely with the experimental results in all the actinide region. The predicted half-lives follow the experimental data trend.
From an adjustment on a recent selected data set of partial α-decay half-lives of 344 ground stat... more From an adjustment on a recent selected data set of partial α-decay half-lives of 344 ground state to ground state transitions, analytical formulas are proposed for log 10 T 1/2 (s) depending or not on the angular momentum of the α particle. In particular, an expression allows to reproduce precisely the partial α-decay half-lives of even-even heavy nuclei and, then, to predict accurately the partial α-decay half-lives of other very heavy elements from the experimental or predicted Q α. Comparisons have been done with other empirical approaches. Moreover, the potential barrier against α-decay or α-capture has been determined within a liquid drop model including a proximity energy term. Simple expressions are provided to calculate the potential barrier radius and height.
We report on a comprehensive systematics of fusion-evaporation and/or fusionfission cross section... more We report on a comprehensive systematics of fusion-evaporation and/or fusionfission cross sections for a very large variety of systems over an energy range 4A-155A MeV. Scaled by the reaction cross sections, fusion cross sections do not show a universal behavior valid for all systems although a high degree of correlation is present when data are ordered by the system mass asymmetry. For the rather light and close to mass-symmetric systems the main characteristics of the complete and incomplete fusion excitation functions can be precisely determined. Despite an evident lack of data above 15A MeV for all heavy systems the available data suggests that geometrical effects could explain the persistence of incomplete fusion at incident energies as high as 155A MeV.
EPJ manuscript No. (will be inserted by the editor) On the liquid drop model mass formulae and ch... more EPJ manuscript No. (will be inserted by the editor) On the liquid drop model mass formulae and charge radii
A meticulous study of nearly 300 fusion-evaporation cross section data reveals that, when properl... more A meticulous study of nearly 300 fusion-evaporation cross section data reveals that, when properly scaled, fusion excitation function complies with a universal homographic law which is, within experimental errors, reaction system independent. From a such complete and summed complete and incomplete fusion excitation functions extracted are the limiting energy for the complete fusion and the main characteristics (onset, maximum and vanishing) of the incomplete fusion. The DYWAN microscopic transport model correctly predicts the incomplete fusion cross section for incident energies 15A MeV and suggests that the nuclear transparency is at the origin of fusion disappearance. Introduction. – Since mid-seventies of the last century it is consensual that heavy-ion fusion reaction as a function of the center-of-mass energy passes through three distinct regions, that of rising (I), stagnating (II), and falling (III) cross sections, respectively. At low energies, the regions I and II have been...
A meticulous study of nearly 300 fusion-evaporation cross section data reveals that, when properl... more A meticulous study of nearly 300 fusion-evaporation cross section data reveals that, when properly scaled, fusion excitation function complies with a universal homographic law which is, within experimental errors, reaction system independent. From a such complete and summed complete and incomplete fusion excitation functions extracted are the limiting energy for the complete fusion and the main characteristics (onset, maximum and vanishing) of the incomplete fusion. The DYWAN microscopic transport model correctly predicts the incomplete fusion cross section for incident energies 15A MeV and suggests that the nuclear transparency is at the origin of fusion disappearance.
Presented is a universal description of the generalized fusion excitation function which indicate... more Presented is a universal description of the generalized fusion excitation function which indicates that the fusion reaction mechanism should vanish at center-of-mass energy per nucleon of about 13 MeV/nucleon independently of the specific heavy-ion reaction system. Placing reliance on this result and comforted by semiclassical transport model simulations we suggest that the proposed persistence of the incomplete fusion cross sections in the measurement of the 14 N induced reactions on heavy targets at beam energies between 100A and 155A MeV should be attributed to a geometrical participant-spectator-like reaction mechanism.
We report on the comprehensive systematics of nearly 400 fusion-evaporation and/or fusion-fission... more We report on the comprehensive systematics of nearly 400 fusion-evaporation and/or fusion-fission crosssectional data for a very large variety of systems over an energy range ∼3A to 155A MeV. Scaled by the reaction cross section and expressed as a function of the center-of-mass energy per nucleon, the fusion cross section displays a universal behavior. Within experimental errors, this behavior does not depend on system mass, mass asymmetry, or system isospin. The deduced homographic functional dependence for complete and summed complete and incomplete fusion excitation functions is derived from basic strong absorption model formulas for reaction cross sections and allows us to draw the main properties of these functions. The limiting energy for the complete fusion and the main characteristics (onset, maximum, and extinction) of the incomplete fusion excitation functions are determined. The complete fusion reaction process disappears around 6.5 MeV/nucleon and the incomplete one disappears at about 13 MeV/nucleon in the center-of-mass frame. The regularity in fusion data is particularly obvious for the evaporation-residue subset of the data ensemble. Adding the fusion-fission data component does not alter the general data trend but somewhat obscures it owing to the larger uncertainty and/or possible normalization problems.
The linear momentum transfer occurring in central heavy ion collisions is studied within the Land... more The linear momentum transfer occurring in central heavy ion collisions is studied within the Landau Vlasov model. A sensitivity to the equation of state is found for this observable. Assuming the free nucleon-nucleon cross section, a soft compressibility modulus ͑around 210 MeV͒ is required to reproduce the large amount of data available for linear momentum transfer. This result stands for local and nonlocal effective potentials.
The 2p radioactivity half-lives have been calculated within a tunneling process through the poten... more The 2p radioactivity half-lives have been calculated within a tunneling process through the potential barrier determined from the original version of the generalized liquid drop model and quasimolecular shapes. The sparse experimental data on the 2p radioactivity half-lives of the 12 O, 16 Ne, 19 Mg, 45 Fe, 48 Ni, 54 Zn, and 67 Kr nuclei are roughly reproduced when taking into account the Q exp 2p value. An analytic formula is provided to obtain rapidly these different half-lives. Using the Q 2p values extracted from the recent Nubase2020 table, extrapolations to other perhaps possible 2p emitters are proposed. Within the same approach, formulas to determine the 9 Be, 6,7 Li, 3,6 He, and 2,3 H decay half-lives at low excitation energy are also provided.
The alpha decay, the cluster radioactivity and the heavy particle emission half-lives of known an... more The alpha decay, the cluster radioactivity and the heavy particle emission half-lives of known and some still unknown superheavy nuclei have been investigated within the original Generalized Liquid Drop Model and analytic formulas. The Q value has been calculated mainly from the recent NUBASE2020 tables. The agreement between the experimental data and the theoretical predictions of the alpha decay half-lives of the superheavy nuclei is correct and some predictions are provided for unknown nuclei. For some emissions of heavy particles by superheavy nuclei the half-life is comparable to the alpha decay half-lives or even smaller.
Different Liquid Drop Model mass formulae have been studied. They include a Coulomb diffuseness c... more Different Liquid Drop Model mass formulae have been studied. They include a Coulomb diffuseness correction Z 2 /A term and pairing and shell energies of the Thomas-Fermi model. The influence of the selected charge radius, the curvature energy and different forms of the Wigner term has been investigated. Their coefficients have been determined by a least square fitting procedure to 2027 experimental atomic masses. The different fits lead to a surface energy coefficient of 17-18 MeV. A large equivalent rms radius (r0 = 1.22 − 1.24 fm) or a shorter central radius may be used. A rms deviation of 0.54 MeV can be reached between the experimental and theoretical masses. The remaining differences come from the determination of the shell and pairing energies. Mass predictions are given for exotic nuclei.
The efficiency of different mass formulas derived from the liquid drop model including or not the... more The efficiency of different mass formulas derived from the liquid drop model including or not the curvature energy, the Wigner term and different powers of the relative neutron excess I has been determined by a least square fitting procedure to the experimental atomic masses assuming a constant R0;charge/A 1= 3 ratio. The Wigner term and the curvature energy can be used independently to improve the accuracy of the mass formula. The different fits lead to a surface energy coefficient of around 17-18 MeV, a r sharp charge radius r0 of 1.22-1.23 fm and a proton form-factor correction to the Coulomb energy of around 0.9 MeV.
Within the preformed cluster model approach, the values of the preformation factors have been ded... more Within the preformed cluster model approach, the values of the preformation factors have been deduced from the experimental cluster decay half-lives assuming that the decay constant of the heavy-ion emission is the product of the assault frequency, the preformation factor and the penetrability. The law according to which the preformation factors follow a simple dependence on the mass of the cluster was confirmed. Then predictions for some most possible cluster decays are provided.
The occurence of "exotic" shapes in light N=Z α-like nuclei is investigated for 24 Mg+ 12 C and 3... more The occurence of "exotic" shapes in light N=Z α-like nuclei is investigated for 24 Mg+ 12 C and 32 S+ 24 Mg. Various approaches of superdeformed and hyperdeformed bands associated with quasimolecular resonant structures with low spin are presented. For both reactions, exclusive data were collected with the Binary Reaction Spectrometer in coincidence with EUROBALL IV installed at the VIVITRON Tandem facility of Strasbourg. Specific structures with large deformation were selectively populated in binary reactions and their associated γ-decays studied. The analysis of the binary and ternary reaction channels is discussed.
Longitudinal ternary and binary fission barriers of 36 Ar, 56 Ni and 252 Cf nuclei have been dete... more Longitudinal ternary and binary fission barriers of 36 Ar, 56 Ni and 252 Cf nuclei have been determined within a rotational liquid drop model taking into account the nuclear proximity energy. For the light nuclei the heights of the ternary fission barriers become competitive with the binary ones at high angular momenta since the maximum lies at an outer position and has a much higher moment of inertia.
The energy of actinide nuclei has been determined within a generalized liquid drop model taking i... more The energy of actinide nuclei has been determined within a generalized liquid drop model taking into account the proximity energy, the mass and charge asymmetry, an accurate nuclear radius in adding the shell and pairing energies. Double and triple-humped potential barriers appear. The second maximum corresponds to the transition from compact and creviced one-body shapes to two touching ellipsoids. A third minimum and third peak appear in special asymmetric exit channels where one fragment is almost a magic nucleus with a quasi-spherical shape while the other one evolves from oblate to prolate shapes. The heights of the double and triple-humped fission barriers agree precisely with the experimental results in all the actinide region. The predicted half-lives follow the experimental data trend.
From an adjustment on a recent selected data set of partial α-decay half-lives of 344 ground stat... more From an adjustment on a recent selected data set of partial α-decay half-lives of 344 ground state to ground state transitions, analytical formulas are proposed for log 10 T 1/2 (s) depending or not on the angular momentum of the α particle. In particular, an expression allows to reproduce precisely the partial α-decay half-lives of even-even heavy nuclei and, then, to predict accurately the partial α-decay half-lives of other very heavy elements from the experimental or predicted Q α. Comparisons have been done with other empirical approaches. Moreover, the potential barrier against α-decay or α-capture has been determined within a liquid drop model including a proximity energy term. Simple expressions are provided to calculate the potential barrier radius and height.
We report on a comprehensive systematics of fusion-evaporation and/or fusionfission cross section... more We report on a comprehensive systematics of fusion-evaporation and/or fusionfission cross sections for a very large variety of systems over an energy range 4A-155A MeV. Scaled by the reaction cross sections, fusion cross sections do not show a universal behavior valid for all systems although a high degree of correlation is present when data are ordered by the system mass asymmetry. For the rather light and close to mass-symmetric systems the main characteristics of the complete and incomplete fusion excitation functions can be precisely determined. Despite an evident lack of data above 15A MeV for all heavy systems the available data suggests that geometrical effects could explain the persistence of incomplete fusion at incident energies as high as 155A MeV.
EPJ manuscript No. (will be inserted by the editor) On the liquid drop model mass formulae and ch... more EPJ manuscript No. (will be inserted by the editor) On the liquid drop model mass formulae and charge radii
A meticulous study of nearly 300 fusion-evaporation cross section data reveals that, when properl... more A meticulous study of nearly 300 fusion-evaporation cross section data reveals that, when properly scaled, fusion excitation function complies with a universal homographic law which is, within experimental errors, reaction system independent. From a such complete and summed complete and incomplete fusion excitation functions extracted are the limiting energy for the complete fusion and the main characteristics (onset, maximum and vanishing) of the incomplete fusion. The DYWAN microscopic transport model correctly predicts the incomplete fusion cross section for incident energies 15A MeV and suggests that the nuclear transparency is at the origin of fusion disappearance. Introduction. – Since mid-seventies of the last century it is consensual that heavy-ion fusion reaction as a function of the center-of-mass energy passes through three distinct regions, that of rising (I), stagnating (II), and falling (III) cross sections, respectively. At low energies, the regions I and II have been...
A meticulous study of nearly 300 fusion-evaporation cross section data reveals that, when properl... more A meticulous study of nearly 300 fusion-evaporation cross section data reveals that, when properly scaled, fusion excitation function complies with a universal homographic law which is, within experimental errors, reaction system independent. From a such complete and summed complete and incomplete fusion excitation functions extracted are the limiting energy for the complete fusion and the main characteristics (onset, maximum and vanishing) of the incomplete fusion. The DYWAN microscopic transport model correctly predicts the incomplete fusion cross section for incident energies 15A MeV and suggests that the nuclear transparency is at the origin of fusion disappearance.
Presented is a universal description of the generalized fusion excitation function which indicate... more Presented is a universal description of the generalized fusion excitation function which indicates that the fusion reaction mechanism should vanish at center-of-mass energy per nucleon of about 13 MeV/nucleon independently of the specific heavy-ion reaction system. Placing reliance on this result and comforted by semiclassical transport model simulations we suggest that the proposed persistence of the incomplete fusion cross sections in the measurement of the 14 N induced reactions on heavy targets at beam energies between 100A and 155A MeV should be attributed to a geometrical participant-spectator-like reaction mechanism.
We report on the comprehensive systematics of nearly 400 fusion-evaporation and/or fusion-fission... more We report on the comprehensive systematics of nearly 400 fusion-evaporation and/or fusion-fission crosssectional data for a very large variety of systems over an energy range ∼3A to 155A MeV. Scaled by the reaction cross section and expressed as a function of the center-of-mass energy per nucleon, the fusion cross section displays a universal behavior. Within experimental errors, this behavior does not depend on system mass, mass asymmetry, or system isospin. The deduced homographic functional dependence for complete and summed complete and incomplete fusion excitation functions is derived from basic strong absorption model formulas for reaction cross sections and allows us to draw the main properties of these functions. The limiting energy for the complete fusion and the main characteristics (onset, maximum, and extinction) of the incomplete fusion excitation functions are determined. The complete fusion reaction process disappears around 6.5 MeV/nucleon and the incomplete one disappears at about 13 MeV/nucleon in the center-of-mass frame. The regularity in fusion data is particularly obvious for the evaporation-residue subset of the data ensemble. Adding the fusion-fission data component does not alter the general data trend but somewhat obscures it owing to the larger uncertainty and/or possible normalization problems.
The linear momentum transfer occurring in central heavy ion collisions is studied within the Land... more The linear momentum transfer occurring in central heavy ion collisions is studied within the Landau Vlasov model. A sensitivity to the equation of state is found for this observable. Assuming the free nucleon-nucleon cross section, a soft compressibility modulus ͑around 210 MeV͒ is required to reproduce the large amount of data available for linear momentum transfer. This result stands for local and nonlocal effective potentials.
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Papers by Guy ROYER