Doru Delion - Academia.edu (original) (raw)

Papers by Doru Delion

Probing Nuclear Structure by Cold Emission Processes

AIP Conference Proceedings, 2008

Cold emission processes (one and two-proton emission, alpha-decay, heavy cluster emission and col... more Cold emission processes (one and two-proton emission, alpha-decay, heavy cluster emission and cold binary or ternary fission) are presently among important tools to investigate the structure of rare nuclei far from the stability line. We analyze the coupling between collective excitations of the emitted fragments and the relative motion, in terms of the coupled channels technique. It turns out that partial decay widths to excited states of emitted fragments are very sensitive to the nuclear structure details.

Physical Review C, 2015

We systematically analyze the coherence length in even-even nuclei. The pairing coherence length ... more We systematically analyze the coherence length in even-even nuclei. The pairing coherence length in the spin-singlet channel for the effective density dependent delta (DDD) and Gaussian interaction is estimated. We consider in our calculations bound states as well as narrow resonances. It turns out that the pairing gaps given by the DDD interaction are similar to those of the Gaussian potential if one renormalizes the radial width to the nuclear radius. The correlations induced by the pairing interaction have in all considered cases a long range character inside the nucleus and decrease towards the surface. The mean coherence length is larger than the geometrical radius for light nuclei and approaches this value for heavy nuclei. The effect of the temperature and states in continuum is investigated. Strong shell effects are evidenced, especially for protons. We generalize this concept to quartets by considering similar relations, but between proton and neutron pairs. The quartet coherence length has a similar shape, but with larger values on the nuclear surface. We evidence the important role of proton-neutron correlations by estimating the so-called alpha coherence length, which takes into account the overlap with the proton-neutron part of the α-particle wave function. It turns out that it does not depend on the nuclear size and has a value comparable to the free αparticle radius. We have shown that pairing correlations are mainly concentrated inside the nucleus, while quarteting correlations are connected to the nuclear surface.

PURE α- 208 Pb STATES IN 212 Po REVEALED BY THEIR ENHANCED E1 DECAYS: A NOVEL α CLUSTERING

International Journal of Modern Physics E, 2011

Excited states in 212 Po have been populated by α transfer using the 208 Pb (18 O ,14 C ) reactio... more Excited states in 212 Po have been populated by α transfer using the 208 Pb (18 O ,14 C ) reaction and studied with the Euroball γ multidetector array. Very enhanced E1 transitions have been revealed by very short lifetimes measured by the DSAM method, found in the [0.1-1.4] ps range. The emitting states, which have non-natural parity values, are the fingerprints of the "α-208 Pb " structure present in 212 Po . They are in the same excitation-energy range as the states issued from shell-model configurations.

Collective M1 and M3 properties of deformed nuclei within the generalized coherent state model

Coupled Channels Methods

Lecture Notes in Physics, 2010

ABSTRACT The most general procedure to describe the emission of deformed fragments within a pheno... more ABSTRACT The most general procedure to describe the emission of deformed fragments within a phenomenological approach is the coupled channels method. We analyze various methods to integrate the coupled channels system of differential equations describing emission processes, namely (a) numerical integration, (b) diagonalisation method, (c) analytical continuation method, (d) distorted wave approach and (e) two potential method. These methods are general, not depending upon the concrete structure of the emitted fragments. We then discuss the intrinsic system of coordinate, adiabatic approach, emission from triaxial nuclei, the coupling with rotation and vibration of the heavy fragment.

Lecture Notes in Physics, 2010

Physical Review C, 1994

A microscopic description of alpha decay of odd mass nuclei is given for axially deformed nuclei.... more 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.

Physical Review C, 2003

Microscopic description of low-lying two-phonon states in even-even nuclei is introduced. The mai... more Microscopic description of low-lying two-phonon states in even-even nuclei is introduced. The main building blocks are the quasiparticle random-phase approximation ͑QRPA͒ phonons. A realistic microscopic nuclear Hamiltonian, based on the Bonn one-boson-exchange potential, is diagonalized in a basis containing onephonon and two-phonon components, coupled to a given angular momentum and parity. The QRPA equations are directly used in deriving the equations of motion for the two-phonon states. The Pauli principle is taken into account by diagonalizing the metric matrix and discarding the zero-norm states. The electromagnetic transition matrix elements are derived in terms of the metric matrix. The model has been applied to the 106 Pd and 108 Pd nuclei, known to contain two-phonon structures. In spite of its simplicity, the model predicts energies and ratios of B(E2) values in a reasonable agreement with the data.

Physical Review C, 2010

We propose a simple systematics of low lying 2 + 1 energy levels and electromagnetic transitions ... more We propose a simple systematics of low lying 2 + 1 energy levels and electromagnetic transitions in semi-magic isotopic chains Z = 28, 50, 82 and isotonic chains N = 28, 50, 82, 126. To this purpose we use a two-level pairing plus quadrupole Hamiltonian, within the spherical Quasiparticle Random Phase Approximation (QRPA). We derive a simple relation connecting the 2 + 1 energy with the pairing gap and quadrupole-quadupole (QQ) interaction strength. It turns out that the systematics of energy levels and B(E2) values predicted by this simple model is fulfilled with a reasonable accuracy by all available experimental data. Both systematics suggest that not only active nucleons but also those filling closed shells play an important role.

Physical Review C, 2007

We analyze α-decays to ground and 2 + vibrational states in even-even nuclei by using a coupled c... more 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.

Physical Review C, 2003

Anharmonic features of the low-lying collective states in the 98-106 Ru isotopes have been invest... more Anharmonic features of the low-lying collective states in the 98-106 Ru isotopes have been investigated systematically by using the microscopic anharmonic vibrator approach (MAVA). MAVA is based on a realistic microscopic G-matrix Hamiltonian, only slightly renormalized in the adopted large realistic single-particle spaces. This Hamiltonian is used to derive equations of motion for the mixing of one-and two-phonon degrees of freedom starting from collective phonons of the quasiparticle random-phase approximation. Analysis of the level energies and the electric quadrupole decays of the two-phonon type of states indicates that 100 Ru can be interpreted as being a transitional nucleus between the spherical anharmonic vibrator 98 Ru and the quasirotational heavier 102-106 Ru isotopes.

Physical Review C, 2006

We analyze α decays to rotational states in even-even nuclei by using the stationary coupled chan... more 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.

Physical Review C, 1996

A single particle basis consisting of two different harmonic oscillator representations is introd... more A single particle basis consisting of two different harmonic oscillator representations is introduced with the aim of studying microscopically ␣and cluster-decay processes. A correct description of the wave functions at large distances is obtained within a minimal single particle basis. Experimental data corresponding to a large number of ␣ decay transitions from even-even nuclei are well reproduced. ͓S0556-2813͑96͒01406-9͔

Physical Review C, 1994

The deformation properties of the low-lying magnetic dipole excitations, known as scissors mode, ... more The deformation properties of the low-lying magnetic dipole excitations, known as scissors mode, are systematically studied within the framework of the generalized coherent state model. The present description is shown to be closely related to other interacting boson approaches as well as to the geometrical two-rotor model. The results are in good agreement with experiments and consistent with those obtained in other phenomenological as well as microscopic approaches.

Physical Review C, 2005

We show that it is possible to restore the symmetry associated with the Goldstone mode within the... more We show that it is possible to restore the symmetry associated with the Goldstone mode within the Self Consistent Random Phase Approximation (SCRPA) applied to the three-level Lipkin model. We determine one and two-body densities as very convergent expansions in terms of the generators of the RPA basis. We show that SCRPA excitations correspond to the heads of some rotational bands in the exact spectrum. It turns out that the SCRPA eigenmodes for N = 2 coincide with exact solutions, given by the diagonalisation procedure.

Physical Review C, 1992

A microscopic approach to the alpha decay problem in deformed nuclei is presented. The nuclear wa... more A microscopic approach to the alpha decay problem in deformed nuclei is presented. The nuclear wave functions are calculated in the frame of the Nilsson+ BCS approximation, making use of a realistic deformed mean field. A large configuration space has been employed in the calculation of the formation amplitude while the penetration process has been treated within the WKB approximation. The calculated widths agree with the experimental data within a factor of about 3. ES'ects due to deformation are also discussed. Applications are presented for Ra, Rn, and Th isotopes.

Physical Review C, 2001

We give a systematic microscopic description of the ␣ decay to excited states in spherical nuclei... more 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.

Physical Review C, 1992

Angular distributions and the corresponding absolute a decay widths are calculated microscopicall... more 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.

Physical Review C, 1991

The alpha decay of deformed nuclei is studied in the framework of the shell model. It is found th... more The alpha decay of deformed nuclei is studied in the framework of the shell model. It is found that the model is able to describe the clustering of the four nucleons that eventually constitute the alpha particle. The clustering process occurs on the deformed nuclear surface and it is induced by high-lying configurations. The absolute decay width of Rn is calculated and good agreement with experimental data is obtained. Alpha-decay processes are among the oldest branches of microscopic physics. Their analysis, the study, and interpretation of the rich amount of data provided by them, has been fundamental since the beginning of this century to build up modern physics. Yet, many questions still remain unanswered in the understanding of the mechanisms that induce the decay of the o, cluster. Thus, it is not clear whether the Pauli principle acting between the constituent nucleons in the a particle and those in the daughter nucleons has any importance. ' Another question which has been only recently partially clarified, and one which is relevant for this paper, is the role played by high-lying configurations in a decay.

Physical Review C, 2013

We describe electromagnetic and α-decay transitions to low-lying excited states in even-even nucl... more We describe electromagnetic and α-decay transitions to low-lying excited states in even-even nuclei within the coherent state model (CSM). We reproduced the energies and B(E2) values for ground state bands in 40 daughter nuclei with known α-branching ratios to 2 + states. To this purpose we used two parameters, namely the deformation parameter and the strength of the harmonic CSM Hamiltonian. The Hamiltonian describing the αemission process is given by two terms. The first term describes the dynamics of the daughter nucleus. The second α-daughter component contains the monopole potential, estimated within the double folding procedure with M3Y interaction plus a repulsive core simulating Pauli principle and a quadrupole-quadrupole (QQ) interaction. The decaying states are identified with the lowest narrow outgoing resonances in this potential. The α-branching ratios to 2 + states were reproduced by using the QQ strength depending linearly on the deformation parameter, as predicted by CSM. The theoretical intensities to 4 + and 6 + states are in a reasonable agreement with available experimental data. We found out that the QQ coupling strength is by one order of magnitude larger in the region above 208 Pb, where the α clustering is known to be stronger, in comparison to other nuclei. This formalism is able to simultaneously describe electromagnetic and α decays to excited states in spherical, transitional, and well deformed nuclei.

Probing Nuclear Structure by Cold Emission Processes

AIP Conference Proceedings, 2008

Cold emission processes (one and two-proton emission, alpha-decay, heavy cluster emission and col... more Cold emission processes (one and two-proton emission, alpha-decay, heavy cluster emission and cold binary or ternary fission) are presently among important tools to investigate the structure of rare nuclei far from the stability line. We analyze the coupling between collective excitations of the emitted fragments and the relative motion, in terms of the coupled channels technique. It turns out that partial decay widths to excited states of emitted fragments are very sensitive to the nuclear structure details.

Physical Review C, 2015

We systematically analyze the coherence length in even-even nuclei. The pairing coherence length ... more We systematically analyze the coherence length in even-even nuclei. The pairing coherence length in the spin-singlet channel for the effective density dependent delta (DDD) and Gaussian interaction is estimated. We consider in our calculations bound states as well as narrow resonances. It turns out that the pairing gaps given by the DDD interaction are similar to those of the Gaussian potential if one renormalizes the radial width to the nuclear radius. The correlations induced by the pairing interaction have in all considered cases a long range character inside the nucleus and decrease towards the surface. The mean coherence length is larger than the geometrical radius for light nuclei and approaches this value for heavy nuclei. The effect of the temperature and states in continuum is investigated. Strong shell effects are evidenced, especially for protons. We generalize this concept to quartets by considering similar relations, but between proton and neutron pairs. The quartet coherence length has a similar shape, but with larger values on the nuclear surface. We evidence the important role of proton-neutron correlations by estimating the so-called alpha coherence length, which takes into account the overlap with the proton-neutron part of the α-particle wave function. It turns out that it does not depend on the nuclear size and has a value comparable to the free αparticle radius. We have shown that pairing correlations are mainly concentrated inside the nucleus, while quarteting correlations are connected to the nuclear surface.

PURE α- 208 Pb STATES IN 212 Po REVEALED BY THEIR ENHANCED E1 DECAYS: A NOVEL α CLUSTERING

International Journal of Modern Physics E, 2011

Excited states in 212 Po have been populated by α transfer using the 208 Pb (18 O ,14 C ) reactio... more Excited states in 212 Po have been populated by α transfer using the 208 Pb (18 O ,14 C ) reaction and studied with the Euroball γ multidetector array. Very enhanced E1 transitions have been revealed by very short lifetimes measured by the DSAM method, found in the [0.1-1.4] ps range. The emitting states, which have non-natural parity values, are the fingerprints of the "α-208 Pb " structure present in 212 Po . They are in the same excitation-energy range as the states issued from shell-model configurations.

Collective M1 and M3 properties of deformed nuclei within the generalized coherent state model

Coupled Channels Methods

Lecture Notes in Physics, 2010

ABSTRACT The most general procedure to describe the emission of deformed fragments within a pheno... more ABSTRACT The most general procedure to describe the emission of deformed fragments within a phenomenological approach is the coupled channels method. We analyze various methods to integrate the coupled channels system of differential equations describing emission processes, namely (a) numerical integration, (b) diagonalisation method, (c) analytical continuation method, (d) distorted wave approach and (e) two potential method. These methods are general, not depending upon the concrete structure of the emitted fragments. We then discuss the intrinsic system of coordinate, adiabatic approach, emission from triaxial nuclei, the coupling with rotation and vibration of the heavy fragment.

Lecture Notes in Physics, 2010

Physical Review C, 1994

A microscopic description of alpha decay of odd mass nuclei is given for axially deformed nuclei.... more 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.

Physical Review C, 2003

Microscopic description of low-lying two-phonon states in even-even nuclei is introduced. The mai... more Microscopic description of low-lying two-phonon states in even-even nuclei is introduced. The main building blocks are the quasiparticle random-phase approximation ͑QRPA͒ phonons. A realistic microscopic nuclear Hamiltonian, based on the Bonn one-boson-exchange potential, is diagonalized in a basis containing onephonon and two-phonon components, coupled to a given angular momentum and parity. The QRPA equations are directly used in deriving the equations of motion for the two-phonon states. The Pauli principle is taken into account by diagonalizing the metric matrix and discarding the zero-norm states. The electromagnetic transition matrix elements are derived in terms of the metric matrix. The model has been applied to the 106 Pd and 108 Pd nuclei, known to contain two-phonon structures. In spite of its simplicity, the model predicts energies and ratios of B(E2) values in a reasonable agreement with the data.

Physical Review C, 2010

We propose a simple systematics of low lying 2 + 1 energy levels and electromagnetic transitions ... more We propose a simple systematics of low lying 2 + 1 energy levels and electromagnetic transitions in semi-magic isotopic chains Z = 28, 50, 82 and isotonic chains N = 28, 50, 82, 126. To this purpose we use a two-level pairing plus quadrupole Hamiltonian, within the spherical Quasiparticle Random Phase Approximation (QRPA). We derive a simple relation connecting the 2 + 1 energy with the pairing gap and quadrupole-quadupole (QQ) interaction strength. It turns out that the systematics of energy levels and B(E2) values predicted by this simple model is fulfilled with a reasonable accuracy by all available experimental data. Both systematics suggest that not only active nucleons but also those filling closed shells play an important role.

Physical Review C, 2007

We analyze α-decays to ground and 2 + vibrational states in even-even nuclei by using a coupled c... more 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.

Physical Review C, 2003

Anharmonic features of the low-lying collective states in the 98-106 Ru isotopes have been invest... more Anharmonic features of the low-lying collective states in the 98-106 Ru isotopes have been investigated systematically by using the microscopic anharmonic vibrator approach (MAVA). MAVA is based on a realistic microscopic G-matrix Hamiltonian, only slightly renormalized in the adopted large realistic single-particle spaces. This Hamiltonian is used to derive equations of motion for the mixing of one-and two-phonon degrees of freedom starting from collective phonons of the quasiparticle random-phase approximation. Analysis of the level energies and the electric quadrupole decays of the two-phonon type of states indicates that 100 Ru can be interpreted as being a transitional nucleus between the spherical anharmonic vibrator 98 Ru and the quasirotational heavier 102-106 Ru isotopes.

Physical Review C, 2006

We analyze α decays to rotational states in even-even nuclei by using the stationary coupled chan... more 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.

Physical Review C, 1996

A single particle basis consisting of two different harmonic oscillator representations is introd... more A single particle basis consisting of two different harmonic oscillator representations is introduced with the aim of studying microscopically ␣and cluster-decay processes. A correct description of the wave functions at large distances is obtained within a minimal single particle basis. Experimental data corresponding to a large number of ␣ decay transitions from even-even nuclei are well reproduced. ͓S0556-2813͑96͒01406-9͔

Physical Review C, 1994

The deformation properties of the low-lying magnetic dipole excitations, known as scissors mode, ... more The deformation properties of the low-lying magnetic dipole excitations, known as scissors mode, are systematically studied within the framework of the generalized coherent state model. The present description is shown to be closely related to other interacting boson approaches as well as to the geometrical two-rotor model. The results are in good agreement with experiments and consistent with those obtained in other phenomenological as well as microscopic approaches.

Physical Review C, 2005

We show that it is possible to restore the symmetry associated with the Goldstone mode within the... more We show that it is possible to restore the symmetry associated with the Goldstone mode within the Self Consistent Random Phase Approximation (SCRPA) applied to the three-level Lipkin model. We determine one and two-body densities as very convergent expansions in terms of the generators of the RPA basis. We show that SCRPA excitations correspond to the heads of some rotational bands in the exact spectrum. It turns out that the SCRPA eigenmodes for N = 2 coincide with exact solutions, given by the diagonalisation procedure.

Physical Review C, 1992

A microscopic approach to the alpha decay problem in deformed nuclei is presented. The nuclear wa... more A microscopic approach to the alpha decay problem in deformed nuclei is presented. The nuclear wave functions are calculated in the frame of the Nilsson+ BCS approximation, making use of a realistic deformed mean field. A large configuration space has been employed in the calculation of the formation amplitude while the penetration process has been treated within the WKB approximation. The calculated widths agree with the experimental data within a factor of about 3. ES'ects due to deformation are also discussed. Applications are presented for Ra, Rn, and Th isotopes.

Physical Review C, 2001

We give a systematic microscopic description of the ␣ decay to excited states in spherical nuclei... more 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.

Physical Review C, 1992

Angular distributions and the corresponding absolute a decay widths are calculated microscopicall... more 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.

Physical Review C, 1991

The alpha decay of deformed nuclei is studied in the framework of the shell model. It is found th... more The alpha decay of deformed nuclei is studied in the framework of the shell model. It is found that the model is able to describe the clustering of the four nucleons that eventually constitute the alpha particle. The clustering process occurs on the deformed nuclear surface and it is induced by high-lying configurations. The absolute decay width of Rn is calculated and good agreement with experimental data is obtained. Alpha-decay processes are among the oldest branches of microscopic physics. Their analysis, the study, and interpretation of the rich amount of data provided by them, has been fundamental since the beginning of this century to build up modern physics. Yet, many questions still remain unanswered in the understanding of the mechanisms that induce the decay of the o, cluster. Thus, it is not clear whether the Pauli principle acting between the constituent nucleons in the a particle and those in the daughter nucleons has any importance. ' Another question which has been only recently partially clarified, and one which is relevant for this paper, is the role played by high-lying configurations in a decay.

Physical Review C, 2013

We describe electromagnetic and α-decay transitions to low-lying excited states in even-even nucl... more We describe electromagnetic and α-decay transitions to low-lying excited states in even-even nuclei within the coherent state model (CSM). We reproduced the energies and B(E2) values for ground state bands in 40 daughter nuclei with known α-branching ratios to 2 + states. To this purpose we used two parameters, namely the deformation parameter and the strength of the harmonic CSM Hamiltonian. The Hamiltonian describing the αemission process is given by two terms. The first term describes the dynamics of the daughter nucleus. The second α-daughter component contains the monopole potential, estimated within the double folding procedure with M3Y interaction plus a repulsive core simulating Pauli principle and a quadrupole-quadrupole (QQ) interaction. The decaying states are identified with the lowest narrow outgoing resonances in this potential. The α-branching ratios to 2 + states were reproduced by using the QQ strength depending linearly on the deformation parameter, as predicted by CSM. The theoretical intensities to 4 + and 6 + states are in a reasonable agreement with available experimental data. We found out that the QQ coupling strength is by one order of magnitude larger in the region above 208 Pb, where the α clustering is known to be stronger, in comparison to other nuclei. This formalism is able to simultaneously describe electromagnetic and α decays to excited states in spherical, transitional, and well deformed nuclei.