52
P. Bansal et al.
densities of 2–3 times the normal nuclear matter density can be formed in a controlled laboratory environment. This compressed phase of nuclear matter is followed
by the expansion in which compressed matter cools down and density drops much
lower than the normal nuclear matter density. At intermediate energies, the reactions produce fragments of all sizes which include free nucleons (FNs, A f rag = 1),
light clusters (LCs, 2≤A f rag ≤4), medium mass fragments (MMFs, 5≤A f rag ≤9),
intermediate mass fragments (IMFs, 5≤A f rag ≤30%A), and heavy mass fragments
(HMFs, 15%A≤A f rag ≤30%A), where A is the mass of either projectile or target
and A f rag is the mass of produced fragment. This phenomenon is called as multifragmentation. From the experimental point of view, multifragmentation is viewed
as a promising observable to investigate the liquid–gas phase co-existence of nuclear
matter [1]. Various studies showed that the structure of fragmentation is influenced
by the incident energy [2, 3], impact parameter [2], mass of the colliding nuclei [4–7]
as well as by the asymmetry [8, 9] of reaction pairs. In literature, there are many
studies present on the multiplicity of IMFs as a function of incident energy [2, 4–6,
10–19] which concluded that the yield of IMFs first increases with energy attains
a maxima and then starts decreasing with further increase in energy. Recently, one
of us and collaborators [20] studied the behavior of yield of HMFs and MMFs with
incident energy and noticed the rise and fall behavior with energy.
At the same time, due to the existing and upcoming radioactive ion beam (RIB)
facilities [21], an increasing interest has been seen in the nuclei away from the line
of stability. Hence, the present study is also concerned about the reactions including
neutron-rich nuclei and in this direction, isospin effects on the peak energy production of IMFs [10, 22–26] will be accounted for. The isospin effects on the yield of
IMFs at 40 AMeV incident energy for isotopic reaction pairs of
112 Sn +
112 Sn and
124 Sn +
124 Sn are studied by the MSU group [22]. Dempsey et al. [23] suggested
isospin effects in the neck fragmentation by studying the semi-peripheral collisions
of
124,136 Xe +
112,124 Sn at 55 AMeV. Miller et al. [24] studied the isospin dependence
of fragment production in the reactions of
58 Fe +
58 Fe and
58 Ni +
58 Ni at incident
energies ranging between 45 and 105 AMeV. It is seen that more IMFs are emitted
as a function of charged particle multiplicity in case of neutron-rich system in comparison to isospin symmetric system at energies between 45 and 75 AMeV, while
at 105 AMeV, the distinction between the yields obtained from two systems disappears. Kaur et al. [10] also studied the isospin effects on the multiplicity of IMFs for
isotopic reaction pairs
40 Ca +
40 Ca,
44 Ca +
44 Ca,
52 Ca +
52 Ca, and
60 Ca +
60 Ca and
isobaric reaction pairs
120 Xe +
120 Xe,
120 Pd +
120 Pd, and
120 Zr +
120 Zr. At the same
time, medium and heavy mass fragments are also produced in multifragmentation
and their dynamics maybe quite different in comparison to light clusters owing to
their different origin. From the literature survey, one finds that unfortunately, there
is no study on the effect of neutron content of colliding pairs on the production of
MMFs and HMFs. It would be interesting to see the role of isospin degree of freedom on the production of different mass fragments, for example, HMFs, MMFs and
IMFs. Here, we will analyze the effect of isospin asymmetry of reacting partners on
the peak energy production of HMFs and MMFs and will try to correlate the effect of
P. Bansal et al.
densities of 2–3 times the normal nuclear matter density can be formed in a controlled laboratory environment. This compressed phase of nuclear matter is followed
by the expansion in which compressed matter cools down and density drops much
lower than the normal nuclear matter density. At intermediate energies, the reactions produce fragments of all sizes which include free nucleons (FNs, A f rag = 1),
light clusters (LCs, 2≤A f rag ≤4), medium mass fragments (MMFs, 5≤A f rag ≤9),
intermediate mass fragments (IMFs, 5≤A f rag ≤30%A), and heavy mass fragments
(HMFs, 15%A≤A f rag ≤30%A), where A is the mass of either projectile or target
and A f rag is the mass of produced fragment. This phenomenon is called as multifragmentation. From the experimental point of view, multifragmentation is viewed
as a promising observable to investigate the liquid–gas phase co-existence of nuclear
matter [1]. Various studies showed that the structure of fragmentation is influenced
by the incident energy [2, 3], impact parameter [2], mass of the colliding nuclei [4–7]
as well as by the asymmetry [8, 9] of reaction pairs. In literature, there are many
studies present on the multiplicity of IMFs as a function of incident energy [2, 4–6,
10–19] which concluded that the yield of IMFs first increases with energy attains
a maxima and then starts decreasing with further increase in energy. Recently, one
of us and collaborators [20] studied the behavior of yield of HMFs and MMFs with
incident energy and noticed the rise and fall behavior with energy.
At the same time, due to the existing and upcoming radioactive ion beam (RIB)
facilities [21], an increasing interest has been seen in the nuclei away from the line
of stability. Hence, the present study is also concerned about the reactions including
neutron-rich nuclei and in this direction, isospin effects on the peak energy production of IMFs [10, 22–26] will be accounted for. The isospin effects on the yield of
IMFs at 40 AMeV incident energy for isotopic reaction pairs of
112 Sn +
112 Sn and
124 Sn +
124 Sn are studied by the MSU group [22]. Dempsey et al. [23] suggested
isospin effects in the neck fragmentation by studying the semi-peripheral collisions
of
124,136 Xe +
112,124 Sn at 55 AMeV. Miller et al. [24] studied the isospin dependence
of fragment production in the reactions of
58 Fe +
58 Fe and
58 Ni +
58 Ni at incident
energies ranging between 45 and 105 AMeV. It is seen that more IMFs are emitted
as a function of charged particle multiplicity in case of neutron-rich system in comparison to isospin symmetric system at energies between 45 and 75 AMeV, while
at 105 AMeV, the distinction between the yields obtained from two systems disappears. Kaur et al. [10] also studied the isospin effects on the multiplicity of IMFs for
isotopic reaction pairs
40 Ca +
40 Ca,
44 Ca +
44 Ca,
52 Ca +
52 Ca, and
60 Ca +
60 Ca and
isobaric reaction pairs
120 Xe +
120 Xe,
120 Pd +
120 Pd, and
120 Zr +
120 Zr. At the same
time, medium and heavy mass fragments are also produced in multifragmentation
and their dynamics maybe quite different in comparison to light clusters owing to
their different origin. From the literature survey, one finds that unfortunately, there
is no study on the effect of neutron content of colliding pairs on the production of
MMFs and HMFs. It would be interesting to see the role of isospin degree of freedom on the production of different mass fragments, for example, HMFs, MMFs and
IMFs. Here, we will analyze the effect of isospin asymmetry of reacting partners on
the peak energy production of HMFs and MMFs and will try to correlate the effect of