Title: Clustering effects and decay analysis of the light mass N=Z and N≠ Z composite systems formed in heavy ion collisions
Speaker: Prof. Bir Bikram Singh, Department of Physics,Sri Guru Granth Sahib World University, Punjab
Venue: IOP Lecture Hall
Date: 2016-Dec-06 16:00:00
Abstract: We investigate the clustering effects in light mass N=Z and N≠Z
composite systems 20Ne*, 28Si*, 40Ca* and 21,22Ne*, 39K*,
respectively, formed in low energy heavy ion reactions at different
excitation energies, within the collective clusterization approach of
the dynamical cluster-decay model (DCM) of Gupta and collaborators
based on quantum mechanical fragmentation theory (QMFT). Considering
quadrupole deformated and compact orientated nuclei, a comparative
decay analysis of these systems has been undertaken for the emission
of different intermediate mass fragments (IMFs)/clusters,
specifically the IMFs having Z=3, 4 and 5 (or Z=7, 6 and 5
complimentary fragments from the 20Ne* and 21,22Ne* composite
systems) which are having the experimental data available for their
Z-distribution. Quite interestingly, the QMFT supports clustering in
N=Z (20Ne*, 28Si*) and N≠Z (21,22Ne*) nuclear systems at
excitation energies corresponding to their respective decay
thresholds/resonant-state energies for the 4α, 16O cluster and
non- α cluster 14C (more so in 22Ne* N≠Z composite
system), supported by the Ikeda diagrams, taking into account the
proper pairing strength in the temperature dependent liquid drop
energies. Within the DCM, we notice that at higher excitation
energies in addition to xα (where x is an integer) type clusters
from N=Z composite systems and xn-xα type clusters from
N≠Z composite systems, np-xα type clusters are relatively
quite dominant, with larger preformation probability due to the
decreased pairing strength at higher temperatures in the liquid drop
energies. Also, the study reveals the presence of competing reaction
mechanisms of compound nucleus (fusion-fission, FF) and of
non-compound nucleus origin (deep inelastic orbiting, DIO) in the
decay of very light mass composite systems 20,21,22Ne* and 28Si* at
different excitation energies. The DIO contribution in the IMFs cross
section σIMFs is extracted for these composite systems, which is
given as the sum of FF cross section σFF and DIO cross section
σDIO. The DCM calculated FF cross-sections are in good agreement
with the available experimental data.
