Recent results of measurements of evaporation residue excitation functions for19F+194,196,198Pt and16,18O+198Pt systems with HYRA spectrometer at IUAC

B.R Behera

doi:10.1051/epjconf/20158600003

Abstract

In this talk results of the evaporation residue (ER) cross sections for the 19 F+ 194,196,198 Pt (forming compound nuclei 213,215,217 Fr) and 16,18 O+ 198 Pt (forming compound nuclei 214,216 Rn) systems measured at Hybrid Recoil mass Analyzer (HYRA) spectrometer installed at the Pelletron+LINAC accelerator facility of the Inter University Accelerator Center (IUAC), New Delhi are reported. The survival probabilities of 215 Fr and 217 Fr with neutron numbers N = 126 are found to be lower than the survival probabilities of 215 Fr and 217 Fr with neutron numbers N = 128 and 130 respectively. Statistical model analysis of the ER cross sections show that an excitation energy dependent scaling factor of the finite-range rotating liquid drop model fission barrier is necessary to fit the experimental data. For the case of 214,216 Rn, the experimental ER cross sections are compared with the predictions from the statistical model calculations of compound nuclear decay where Kramer’s fission width is used. The strength of nuclear dissipation is treated as a free parameter in the calculations to fit the experimental data.

Highlights

Another interesting features of heavy ion induced fusion-fission reactions is the observation that for compound nucleus (CN) at high excitation energies, prescission multiplicity data of light particles and GDR γ point to a hindrance or slowing down of the fission process compared with that given by the transition-state theory of Bohr and Wheeler [5,6,10]
Recent results of evaporation residue (ER) excitation functions for 19F+194,196,198Pt and 16,18O+194,198Pt systems measured at HYRA spectrometer at Inter University Accelerator Center (IUAC) are summarized
Detail statistical model calculations are performed for the interpretation of the data

Summary

Introduction

Another interesting features of heavy ion induced fusion-fission reactions is the observation that for CN at high excitation energies (temperature >1 MeV), prescission multiplicity data of light particles and GDR γ point to a hindrance or slowing down of the fission process compared with that given by the transition-state theory of Bohr and Wheeler [5,6,10]. The above observations suggest that improvements in fission modeling are necessary where effects such as the roles of excitation energy and shape (of the CN) dependence of dissipation need to be further investigated Experimental data on both pre-scission multiplicities and ER crosssections of a large number of systems are required for a better understanding of the fission process. EPJ Web of Conferences of heavy nuclei with large excitation energies With these above two broad motivations in mind, a series of experiments were performed to measure the ER excitation functions for 19F+194,196,198Pt (beam energies in the range of 101-137.3 MeV) and 16,18O+194,198Pt system (beam energies in the range of 77-106 MeV) at the HYRA spectrometer of IUAC, New Delhi Pelletron+LINAC accelerator facilities.

Experimental Details

Summary and Conclusions