Electromagnetic dissociation of 11li and soft dipole mode

Suzuki, Y.; Tosaka, Y.

doi:10.1016/0375-9474(90)90221-7

Cited by 57 publications

(36 citation statements)

References 18 publications

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“…If the system has a core plus two-nucleon structure and the first term on the right-hand side of the above equation does not contribute to the E1 strength, we obtain the non-energyweighted cluster sum rule [54,55]:…”

Section: E Validity Of α + N + N Three-body Picturementioning

confidence: 99%

Electric dipole response ofHe6: Halo-neutron and core excitations

2014

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Electric dipole (E1) response of 6 He is studied with a fully microscopic six-body calculation. The wave functions for the ground and excited states are expressed as a superposition of explicitly correlated Gaussians. Final state interactions of three-body decay channels are explicitly taken into account. The ground state properties and the low-energy E1 strength are obtained consistently with observations. Two main peaks as well as several small peaks are found in the E1 strength function. The peak at the high-energy region indicates a typical macroscopic picture of the giant dipole resonance, the out-of-phase proton-neutron motion. The transition densities of the lower-lying peaks exhibit in-phase proton-neutron motion in the internal region, out-of-phase motion near the surface region, and spatially extended neutron oscillation, indicating a soft-dipole mode and its vibrationally excited mode. The compressional dipole strength is also examined in relation to the soft-dipole mode.

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Section: E Validity Of α + N + N Three-body Picturementioning

confidence: 99%

Electric dipole response ofHe6: Halo-neutron and core excitations

2014

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“…The Coulomb breakup is induced mainly by the electric dipole component of the target Coulomb field. The large Coulomb breakup cross section is related to the E1 strength distribution at low excitation energy [3].A question concerning the property of this low lying dipole strength is whether or not it has a resonance character representing the vibration of the halo neutron and the core [4].…”

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Coulomb breakup mechanism of neutron drip-line nuclei

1994

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The mechanism of the Coulomb breakup reaction of the projectile nuclei with neutron halo structure is investigated by the time-dependent Schrodinger equation in three-dimensional space. The time evolution of the internal wave function between the core nucleus and the halo neutron is calculated in the target Coulomb field treated as the time-dependent external field. Calculations are done for the "Be+ Pb system for which an experiment has been done recently. The calculated results support the picture of free-particle breakup mechanism: Only the core nucleus is affected by the target Coulomb field, while the halo neutron moves independently. As a result, we obtain large transverse and small longitudinal difference in the relative velocity between the core and the neutron after the breakup. The origin of the longitudinal velocity difference observed experimentally is left unresolved in our approach. PACS number(s): 25.60.+v, 25.70.De In the light nuclei around the neutron drip line, the neutron halo structure has been observed systematically [1]. Besides the spatially extended density distribution of the halo neutron, the drip-line nuclei have such characteristics that they easily breakup into the core nucleus and the halo neutron(s). Especially the large breakup cross section has been observed in the Coulomb excitation [2]. The Coulomb breakup is induced mainly by the electric dipole component of the target Coulomb field. The large Coulomb breakup cross section is related to the E1 strength distribution at low excitation energy [3].A question concerning the property of this low lying dipole strength is whether or not it has a resonance character representing the vibration of the halo neutron and the core [4].In the recent coincident measurements of the core and the halo neutron, the significant difference in the longitudinal velocity distribution between them has been observed in the Coulomb breakup reaction of "Li [5] and "Be [6]. It has been explained in terms of the Coulomb postacceleration effect by assuming the direct breakup mechanism [5,6]. Before the closest approach point where the breakup is assumed to occur, the projectile is decelerated by the target Coulomb field. After the closest approach point the core and the halo neutron move independently. Since only the core nucleus is accelerated by the target Coulomb field, the velocity difference is expected to occur between the core and the neutron.On the other hand, if the breakup proceeds by way of the resonant state, the core and the halo neutron would move together until they decay and the velocity difference would be small. Therefore, the measurements of the velocity difference are expected to be useful as a clock to measure the lifetime of the resonant state.The Coulomb postacceleration is a higher order effect in the perturbative treatment of the Coulomb excitation. To calculate the higher order terms is not easy in the breakup reaction into continuum states. Several approaches have been applied including a classical treatment of the breakup [7], a di...

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“…This nucleus has an interaction cross section which is large compared to those of its neighbor nuclei [1]. In its dominant reaction channel, dissociation into 9 Li plus two neutrons, both the neutrons and the fragment have been separately found to have sharply forward-peaked angular distributions [2][3][4][5]. These results have been interpreted to mean that n Li should be thought of as having a 9 Li core immersed in a halo of two neutrons, perhaps correlated as a dineutron [6].…”

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“…In its dominant reaction channel, dissociation into 9 Li plus two neutrons, both the neutrons and the fragment have been separately found to have sharply forward-peaked angular distributions [2][3][4][5]. These results have been interpreted to mean that n Li should be thought of as having a 9 Li core immersed in a halo of two neutrons, perhaps correlated as a dineutron [6]. Furthermore, the large dissociation cross section of 11 Li by a high-Z target may then be the result of an electric dipole excitation to a "soft" dipole resonance located at an excitation energy much lower than the universal giant dipole resonance [7,8].…”

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Coulomb dissociation ofLi11

et al. 1993

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Kinematically complete measurements for Coulomb dissociation of n Li into 9 Li + 2« were made at 28 MeV/nucleon. The n-n correlation function suggests a large source size for the two-neutron emission. The electromagnetic excitation spectrum of n Li has a peak, as anticipated in low-energy dipole resonance models, but a large post-breakup Coulomb acceleration of the 9 Li fragment is observed, indicating a very short lifetime of the excited state and favoring direct breakup as the dissociation mechanism.

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Electromagnetic dissociation of 11li and soft dipole mode

Cited by 57 publications

References 18 publications

Electric dipole response ofHe6: Halo-neutron and core excitations

Electric dipole response ofHe6: Halo-neutron and core excitations

Coulomb breakup mechanism of neutron drip-line nuclei

Coulomb dissociation ofLi11

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