Isospin dependence of intermediate mass fragment production in heavy-ion collisions at<i>E</i>/<i>A</i>=55 MeV

Dempsey, James F.; Charity, R. J.; Sobotka, L. G.; Kunde, G. J.; Gaff, S. J.; Gelbke, C. K.; Glasmacher, T.; Huang, M. J.; Lemmon, R. C.; Lynch, W. G.; Manduci, L.; Martin, L.; Tsang, M. B.; Agnihotri, D. K.; Djerroud, B.; Schröder, W.; Skulski, W.; Tōke, J.; Friedman, William A.

doi:10.1103/physrevc.54.1710

Cited by 122 publications

(99 citation statements)

References 24 publications

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“…The potential mechanisms of mid-rapidity emissions, as e.g. neck formation, and the isospin effects associated with it [39,40] are closely connected to several dynamical and statistical aspects of hot fragmentation, among them the isotopic separation expected in the liquid-gas coexistence zone [41][42][43]. These topics are the subjects of other plenary talks at this conference.…”

Section: Useful Reactionsmentioning

confidence: 99%

Hot fragmentation of nuclei

Trautmann¹

2001

Nuclear Physics A

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Today, we have a variety of reactions at hand that can be used to multi-fragment nuclei. In many of these reactions even several sources of fragments can be discerned and characterized.There is overwhelming evidence that these sources of fragments are hot. It is already less clear whether heat by itself is sufficient to initiate the fragment decay. What causes fragmentation, and when and how are the fragments (pre)formed? These questions have remained as much a challenge as the complementary class of questions to which they are related: What observations derive their significance from the liquid-gas phase behavior of extended nuclear matter? And, can we observe a phase transition in finite nuclei?Recent developments, largely coming from complex analyses of data sets measured in 4-π-type experiments as well as from calculations based on advanced theoretical concepts, will be discussed.

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Section: Useful Reactionsmentioning

confidence: 99%

Hot fragmentation of nuclei

Trautmann¹

2001

Nuclear Physics A

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“…An enhanced production of neutron rich H and He isotopes from the neck region has been seen experimentally in mid-peripheral collisions [8,9], while a favored emission of more symmetric heavy clusters in the mid-rapidity region has also been shown [10]. Quite neutron deficient residues have also been seen in intermediate energy reactions [11,12].…”

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confidence: 91%

Inhomogeneous isospin distribution in the reactions of28Si+112Snand
Veselský
¹
,
Ibbotson
²
,
Laforest
³

et al. 2000
Phys. Rev. C

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We have created quasiprojectiles of varying isospin via peripheral reactions of 28 Si + 112 Sn and 124 Sn at 30 and 50 MeV/nucleon. The quasiprojectiles have been reconstructed from completely isotopically identified fragments. The difference in N/Z of the reconstructed quasiprojectiles allows the investigation of the disassembly as a function of the isospin of the fragmenting system. The isobaric yield ratio 3 H/ 3 He depends strongly on N/Z ratio of quasiprojectiles. The dependences of mean fragment multiplicity and mean N/Z ratio of the fragments on N/Z ratio of the quasiprojectile are different for light charged particles and intermediate mass fragments. Observation of a different N/Z ratio of light charged particles and intermediate mass fragments is consistent with an inhomogeneous distribution of isospin in the fragmenting system. There has been significant interest in multifragmentation of excited nuclear matter for many years. While there has been some success in understanding the process of multifragmentation and describing this phenomenon in terms of a liquid gas phase transition [1], those efforts have often treated the nucleus as a single component nuclear liquid. In fact, the nucleus is a two component nuclear liquid. Early work by Lamb [2] laid the foundations for treating the nucleus as a two component system although the results were not connected to multifragmentation. Statistical calculations describing multifragment disassembly predicted that much of the neutron excess would be observed as free neutrons [3]. Thermodynamic calculations by Müller and Serot [4] lead us to the idea that, for the very neutron rich systems, there may exist a distribution of the excited nuclear matter into a neutron rich gas and a more symmetric liquid. It is predicted by both lattice gas and mean field calculations [5,6] that fragmentation of a system of asymmetric nuclear matter will express the characteristics of a two component system. This would result in a second order phase transition. Also within a dynamical code, constructed to study influence of charge asymmetry on spinoidal decomposition of nuclear matter at sub-saturation densities, differences in the fragmentation are seen as a function of isospin asymmetry [7].The difference of the mean N/Z ratio of the light charged particles with Z f ≤ 2 ( LCPs ) and of the intermediate mass fragments with Z f ≥ 3 ( IMFs ) may be a possible experimental signature of a separation into a gas ( resulting mostly in emitted LCPs ) and a liquid ( IMFs ). An enhanced production of neutron rich H and He isotopes from the neck region has been seen experimentally in mid-peripheral collisions [8,9], while a favored emission of more symmetric heavy clusters in the mid-rapidity region has also been shown [10]. Quite neutron deficient residues have also been seen in intermediate energy reactions [11,12]. Recent results from the reaction of 112,124 Sn + 112,124 Sn indicate that the relative abundance of free neutrons increases as the neutron content of the colliding system increas...

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“…In particular, the formation of a neck-like structure in peripheral heavy ion reactions and the impact on the fragmentation mechanism and production of light charged particles has been discussed for a couple of years [7][8][9][10][11][12][13][14][15][16][17][18][19]. It has been suggested that this neck instability can be important for the fast decomposition of matter and is probably neutron rich [20].…”

Section: Introductionmentioning

confidence: 99%

Midrapidity charge distribution in peripheral heavy ion collisions

et al. 2001

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The charge density distribution with respect to the velocity of matter produced in peripheral heavy ion reactions around Fermi energy is investigated. The experimental finding of enhancement of midrapidity matter shows the necessity to include correlations beyond BUU which was performed in the framework of nonlocal kinetic theory. Different theoretical improvements are discussed. While the in-medium cross section changes the number of collisions, it leaves the transferred energy almost unchanged. In contrast the nonlocal scenario changes the energy transferred during collisions and leads to an enhancement of mid-rapidity matter. The renormalisation of quasiparticle energies can be included in nonlocal scenarios and leads to a further enhancement of mid-rapidity matter distribution. This renormalisation is accompanied by a dynamical softening of the equation of state seen in longer oscillation periods of the excited compressional collective mode. We propose to include quasiparticle renormalisation by using the Pauli-rejected collisions which circumvent the problem of backflows in Landau theory. Using the maximum relative velocity of projectile and target like fragments we associate experimental events with impact parameters of the simulations. For peripheral collisions we find a reasonable agreement between experiment and theory. For more central collisions, the velocity damping is higher in one-body simulations than observed experimentally, because of missing cluster formations in the kinetic theory used.

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Isospin dependence of intermediate mass fragment production in heavy-ion collisions atE/A=55 MeV

Cited by 122 publications

References 24 publications

Hot fragmentation of nuclei

Hot fragmentation of nuclei

Inhomogeneous isospin distribution in the reactions of28Si+112Snand
Veselský
¹
,
Ibbotson
²
,
Laforest
³

et al. 2000
Phys. Rev. C

Midrapidity charge distribution in peripheral heavy ion collisions

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Isospin dependence of intermediate mass fragment production in heavy-ion collisions atE/A=55 MeV

Cited by 122 publications

References 24 publications

Hot fragmentation of nuclei

Hot fragmentation of nuclei

Inhomogeneous isospin distribution in the reactions of28Si+112SnandVeselský1, Ibbotson2, Laforest3 et al. 2000Phys. Rev. C

Midrapidity charge distribution in peripheral heavy ion collisions

Contact Info

Product

Resources

About

Inhomogeneous isospin distribution in the reactions of28Si+112Snand
Veselský
¹
,
Ibbotson
²
,
Laforest
³

et al. 2000
Phys. Rev. C