Rohit Sandal - Academia.edu (original) (raw)
Papers by Rohit Sandal
![Research paper thumbnail of Erratum: Effect ofN/Zin pre-scission neutron multiplicity for16,18O+194,198Ptsystems [Phys. Rev. C87, 014604 (2013)]](https://attachments.academia-assets.com/114190458/thumbnails/1.jpg)
](Physical review, Jun 4, 2013
The caption for Fig. 3 contains a typographical error; it should refer to the ordinate as N/Z (ra... more The caption for Fig. 3 contains a typographical error; it should refer to the ordinate as N/Z (rather than β). The correct caption for Fig. 3 should read "Variation in M pre with N/Z for different systems. The experimental values are also shown." We regret the oversight. The results and conclusions of the article are not affected.
Physical review, Apr 30, 2015
Evaporation residue (ER) cross sections for the 16,18 O + 198 Pt reactions are measured in order ... more Evaporation residue (ER) cross sections for the 16,18 O + 198 Pt reactions are measured in order to investigate fission hindrance. Compound nuclei (214,216 Rn) are formed in the above fusion reactions at excitation energies in the range of 40-68 MeV. The experimental ER cross sections are compared with predictions from the statistical model calculations of compound nuclear decay where Kramers' fission width is used. The strength of nuclear dissipation is treated as a free parameter in the statistical model calculations in order to fit the experimental data.
International Journal of Modern Physics E
Multinucleon transfer reactions were measured in interactions of 28Si with 90,94Zr at a near barr... more Multinucleon transfer reactions were measured in interactions of 28Si with 90,94Zr at a near barrier energy using recoil mass separator, Heavy Ion Reaction Analyzer (HIRA) at Inter University Accelerator Centre (IUAC), New Delhi. The effects of shell closure, positive Q-value transfer channels on the relative strengths of ground state and excited state transfer in multinucleon transfer processes were investigated. The kinematic coincidence technique was employed to reduce the background. The m/q ambiguity was resolved by time of flight (TOF) technique. Based on the Q-value considerations, it was observed that pickup channels were predominantly of neutron transfer, whereas, stripping channels were mainly of proton transfer. A 14-element BGO array was used to extract the relative strength of excited state transfer. In interactions of 28Si with 90Zr, it was observed that the ground state and excited states competes for populating all the transfer channels. In reactions of 28Si with 94Z...
Journal of Physics G: Nuclear and Particle Physics, 2015
ABSTRACT
Physical Review C, 2015
Evaporation residue (ER) cross sections for the 16,18 O + 198 Pt reactions are measured in order ... more Evaporation residue (ER) cross sections for the 16,18 O + 198 Pt reactions are measured in order to investigate fission hindrance. Compound nuclei (214,216 Rn) are formed in the above fusion reactions at excitation energies in the range of 40-68 MeV. The experimental ER cross sections are compared with predictions from the statistical model calculations of compound nuclear decay where Kramers' fission width is used. The strength of nuclear dissipation is treated as a free parameter in the statistical model calculations in order to fit the experimental data.
ABSTRACT The pre-scission neutron multiplicities have been studied for 16,18O+194,198Pt at 50, 61... more ABSTRACT The pre-scission neutron multiplicities have been studied for 16,18O+194,198Pt at 50, 61, 71.7, 79 MeV excitation energy populating 210,212,214,216Rn compound nuclei having fissility 0.735, 0.732, 0.729, 0.726 respectively. Fission Time scales were extracted from the measured pre-scission neutron multiplicity and statistical model PACE2. The effect of fissility on fission time scales has been measured. It is found that fission time scales increases in a consistent way with fissility of the compound nuclei (CN) populated. The fission delays extracted for different CN are in good agreement with earlier published data for heavier systems [1, 2]. In the present work it is shown systematically that the fission time scales generally increases with fissility value of CN.
ABSTRACT The high spin states of 131Ba have been populated in the fusion evaporation reaction 122... more ABSTRACT The high spin states of 131Ba have been populated in the fusion evaporation reaction 122Sn(13C,4n)131Ba at Ebeam = 65MeV. The γ transitions belonging to various band structures were detected using an array of fifteen Clover Germanium detectors. Some of new transitions have been placed in high spin states. Spin and parity for a band has been calculated for first time in 131Ba. The said band is interpreted in term of multi-quasiparticle configurations, based on Total Rothian Surfaces (TRS) calculations.
Physical Review C, 2013
Pre-scission neutron multiplicities from fission of the compound nuclei 210,212,214,216 Rn have b... more Pre-scission neutron multiplicities from fission of the compound nuclei 210,212,214,216 Rn have been measured in order to investigate the N/Z dependence of fission hindrance. The Rn isotopes are populated through the fusion of 16,18 O + 194,198 Pt systems and are formed at four excitation energies in the range of 50-79 MeV. The experimental pre-scission neutron yield is compared with predictions from the statistical model of compound nuclear decay containing the strength of nuclear dissipation as a free parameter. The strength of nuclear dissipation obtained in the present analysis does not show any specific dependence on the N/Z values of the fissioning nuclei at large excitation energies. The dissipation strength at the lowest excitation energy, however, indicates a shell closure effect at N = 126 for the 212 Rn isotope.
Physical Review C, 2011
Measurements on multinucleon transfer reactions for 28 Si + 90,94 Zr systems were performed at su... more Measurements on multinucleon transfer reactions for 28 Si + 90,94 Zr systems were performed at sub-and near-barrier energies. The fact that 90 Zr has a closed neutron shell (N = 50) and 94 Zr has four neutrons outside the closed shell, allows us to investigate the effects of shell closure and pairing correlation on multinucleon transfer mechanism. The experiment was performed with pulsed 28 Si beam using the Heavy Ion Reaction Analyzer (HIRA) at Inter University Accelerator Centre (IUAC), New Delhi. Based on the Q-value considerations, it turned out that pickup channels were neutron transfer whereas stripping channels were proton transfer. For the 28 Si + 90 Zr system, the values of the slope parameter for two-neutron pickup turned out to be less than that for one-neutron pickup. The values of the slope parameter were almost the same for two-, three-, and four-neutron pickup channels in the case of the 28 Si + 94 Zr system. The transfer probabilities in the case of the 28 Si + 94 Zr system were much larger than those for the 28 Si + 90 Zr system, further supporting the fact that there is a correlation between the transfer channels and sub-barrier fusion cross-section enhancement. An odd-even staggering was observed in the extracted transfer probabilities at the barrier radius implying the role of pairing correlation in transfer reactions.
Physical Review C, 2012
Measurements of angular distributions for one-and two-proton stripping reactions for 28 Si + 90,9... more Measurements of angular distributions for one-and two-proton stripping reactions for 28 Si + 90,94 Zr systems were performed at 120 MeV. The experiment was carried out with the 28 Si beam at Inter University Accelerator Center, New Delhi. The theoretical calculations were performed using the quantum mechanical coupled reaction channels code FRESCO. The distorted wave Born approximation calculations reproduced the experimental angular distributions for the one-proton transfer channel for both the systems reasonably well but failed for the two-proton transfer channel. Coupled channels calculations including various intermediate states (involving target and projectile inelastic excitations before and/or after transfer) along with the sequential transfer were able to reproduce the two-proton transfer angular distributions for both the systems reasonably well. It seems that at an energy above the Coulomb barrier, there is significant contribution of the indirect multistep and sequential transfer to the two-proton stripping reaction.
Physical Review C, 2014
Background: Several inclusive and few exclusive [evaporation residue (ER) gated] measurements for... more Background: Several inclusive and few exclusive [evaporation residue (ER) gated] measurements for symmetric systems reported in the literature describe the anomalous deviations of light particle evaporation spectra from the statistical model predictions. However, no consistent description exists for these deviations. Purpose: To establish the consistent interpretation of reported anomalous deviations. Method: The inclusive and exclusive measurements of α-particle, proton, and neutron spectra were carried out for the fusion of two relatively symmetric systems 28 Si + 45 Sc (E lab = 125 MeV and l max = 47) and 32 S + 45 Sc (E lab = 125 MeV and l max = 43) leading to the compound nuclei 73 Br and 77 Rb with excitation energies 78 MeV and 71 MeV, respectively. Results: The experimental light particle spectra for both the reactions show anomalous deviations from the statistical model predictions. The charged particles spectra are found to be suppressed, whereas the neutron spectra exhibit a bump at the higher energy tail. These spectra are investigated in terms of the modification of the important ingredients of the statistical model viz. the level density parameter, rescaling of the yrast line, and the use of l value suggested by the dynamical models. Conclusions: It is conjectured that the higher partial waves do not fuse, but result in the formation of a deformed dinuclear system. The binding energy of neutrons is reduced while those for protons and α particles are enhanced in the deformed dinuclear system as compared to those in the shape-equilibrated system. Hence, the higher partial waves inhibit their contributions to the α-particle spectra and lead to the preshape equilibrium of neutrons and protons, with the neutron emission dominating over the proton emission.
Physical review, Jun 4, 2013
The caption for Fig. 3 contains a typographical error; it should refer to the ordinate as N/Z (ra... more The caption for Fig. 3 contains a typographical error; it should refer to the ordinate as N/Z (rather than β). The correct caption for Fig. 3 should read "Variation in M pre with N/Z for different systems. The experimental values are also shown." We regret the oversight. The results and conclusions of the article are not affected.
Physical review, Apr 30, 2015
Evaporation residue (ER) cross sections for the 16,18 O + 198 Pt reactions are measured in order ... more Evaporation residue (ER) cross sections for the 16,18 O + 198 Pt reactions are measured in order to investigate fission hindrance. Compound nuclei (214,216 Rn) are formed in the above fusion reactions at excitation energies in the range of 40-68 MeV. The experimental ER cross sections are compared with predictions from the statistical model calculations of compound nuclear decay where Kramers' fission width is used. The strength of nuclear dissipation is treated as a free parameter in the statistical model calculations in order to fit the experimental data.
International Journal of Modern Physics E
Multinucleon transfer reactions were measured in interactions of 28Si with 90,94Zr at a near barr... more Multinucleon transfer reactions were measured in interactions of 28Si with 90,94Zr at a near barrier energy using recoil mass separator, Heavy Ion Reaction Analyzer (HIRA) at Inter University Accelerator Centre (IUAC), New Delhi. The effects of shell closure, positive Q-value transfer channels on the relative strengths of ground state and excited state transfer in multinucleon transfer processes were investigated. The kinematic coincidence technique was employed to reduce the background. The m/q ambiguity was resolved by time of flight (TOF) technique. Based on the Q-value considerations, it was observed that pickup channels were predominantly of neutron transfer, whereas, stripping channels were mainly of proton transfer. A 14-element BGO array was used to extract the relative strength of excited state transfer. In interactions of 28Si with 90Zr, it was observed that the ground state and excited states competes for populating all the transfer channels. In reactions of 28Si with 94Z...
Journal of Physics G: Nuclear and Particle Physics, 2015
ABSTRACT
Physical Review C, 2015
Evaporation residue (ER) cross sections for the 16,18 O + 198 Pt reactions are measured in order ... more Evaporation residue (ER) cross sections for the 16,18 O + 198 Pt reactions are measured in order to investigate fission hindrance. Compound nuclei (214,216 Rn) are formed in the above fusion reactions at excitation energies in the range of 40-68 MeV. The experimental ER cross sections are compared with predictions from the statistical model calculations of compound nuclear decay where Kramers' fission width is used. The strength of nuclear dissipation is treated as a free parameter in the statistical model calculations in order to fit the experimental data.
ABSTRACT The pre-scission neutron multiplicities have been studied for 16,18O+194,198Pt at 50, 61... more ABSTRACT The pre-scission neutron multiplicities have been studied for 16,18O+194,198Pt at 50, 61, 71.7, 79 MeV excitation energy populating 210,212,214,216Rn compound nuclei having fissility 0.735, 0.732, 0.729, 0.726 respectively. Fission Time scales were extracted from the measured pre-scission neutron multiplicity and statistical model PACE2. The effect of fissility on fission time scales has been measured. It is found that fission time scales increases in a consistent way with fissility of the compound nuclei (CN) populated. The fission delays extracted for different CN are in good agreement with earlier published data for heavier systems [1, 2]. In the present work it is shown systematically that the fission time scales generally increases with fissility value of CN.
ABSTRACT The high spin states of 131Ba have been populated in the fusion evaporation reaction 122... more ABSTRACT The high spin states of 131Ba have been populated in the fusion evaporation reaction 122Sn(13C,4n)131Ba at Ebeam = 65MeV. The γ transitions belonging to various band structures were detected using an array of fifteen Clover Germanium detectors. Some of new transitions have been placed in high spin states. Spin and parity for a band has been calculated for first time in 131Ba. The said band is interpreted in term of multi-quasiparticle configurations, based on Total Rothian Surfaces (TRS) calculations.
Physical Review C, 2013
Pre-scission neutron multiplicities from fission of the compound nuclei 210,212,214,216 Rn have b... more Pre-scission neutron multiplicities from fission of the compound nuclei 210,212,214,216 Rn have been measured in order to investigate the N/Z dependence of fission hindrance. The Rn isotopes are populated through the fusion of 16,18 O + 194,198 Pt systems and are formed at four excitation energies in the range of 50-79 MeV. The experimental pre-scission neutron yield is compared with predictions from the statistical model of compound nuclear decay containing the strength of nuclear dissipation as a free parameter. The strength of nuclear dissipation obtained in the present analysis does not show any specific dependence on the N/Z values of the fissioning nuclei at large excitation energies. The dissipation strength at the lowest excitation energy, however, indicates a shell closure effect at N = 126 for the 212 Rn isotope.
Physical Review C, 2011
Measurements on multinucleon transfer reactions for 28 Si + 90,94 Zr systems were performed at su... more Measurements on multinucleon transfer reactions for 28 Si + 90,94 Zr systems were performed at sub-and near-barrier energies. The fact that 90 Zr has a closed neutron shell (N = 50) and 94 Zr has four neutrons outside the closed shell, allows us to investigate the effects of shell closure and pairing correlation on multinucleon transfer mechanism. The experiment was performed with pulsed 28 Si beam using the Heavy Ion Reaction Analyzer (HIRA) at Inter University Accelerator Centre (IUAC), New Delhi. Based on the Q-value considerations, it turned out that pickup channels were neutron transfer whereas stripping channels were proton transfer. For the 28 Si + 90 Zr system, the values of the slope parameter for two-neutron pickup turned out to be less than that for one-neutron pickup. The values of the slope parameter were almost the same for two-, three-, and four-neutron pickup channels in the case of the 28 Si + 94 Zr system. The transfer probabilities in the case of the 28 Si + 94 Zr system were much larger than those for the 28 Si + 90 Zr system, further supporting the fact that there is a correlation between the transfer channels and sub-barrier fusion cross-section enhancement. An odd-even staggering was observed in the extracted transfer probabilities at the barrier radius implying the role of pairing correlation in transfer reactions.
Physical Review C, 2012
Measurements of angular distributions for one-and two-proton stripping reactions for 28 Si + 90,9... more Measurements of angular distributions for one-and two-proton stripping reactions for 28 Si + 90,94 Zr systems were performed at 120 MeV. The experiment was carried out with the 28 Si beam at Inter University Accelerator Center, New Delhi. The theoretical calculations were performed using the quantum mechanical coupled reaction channels code FRESCO. The distorted wave Born approximation calculations reproduced the experimental angular distributions for the one-proton transfer channel for both the systems reasonably well but failed for the two-proton transfer channel. Coupled channels calculations including various intermediate states (involving target and projectile inelastic excitations before and/or after transfer) along with the sequential transfer were able to reproduce the two-proton transfer angular distributions for both the systems reasonably well. It seems that at an energy above the Coulomb barrier, there is significant contribution of the indirect multistep and sequential transfer to the two-proton stripping reaction.
Physical Review C, 2014
Background: Several inclusive and few exclusive [evaporation residue (ER) gated] measurements for... more Background: Several inclusive and few exclusive [evaporation residue (ER) gated] measurements for symmetric systems reported in the literature describe the anomalous deviations of light particle evaporation spectra from the statistical model predictions. However, no consistent description exists for these deviations. Purpose: To establish the consistent interpretation of reported anomalous deviations. Method: The inclusive and exclusive measurements of α-particle, proton, and neutron spectra were carried out for the fusion of two relatively symmetric systems 28 Si + 45 Sc (E lab = 125 MeV and l max = 47) and 32 S + 45 Sc (E lab = 125 MeV and l max = 43) leading to the compound nuclei 73 Br and 77 Rb with excitation energies 78 MeV and 71 MeV, respectively. Results: The experimental light particle spectra for both the reactions show anomalous deviations from the statistical model predictions. The charged particles spectra are found to be suppressed, whereas the neutron spectra exhibit a bump at the higher energy tail. These spectra are investigated in terms of the modification of the important ingredients of the statistical model viz. the level density parameter, rescaling of the yrast line, and the use of l value suggested by the dynamical models. Conclusions: It is conjectured that the higher partial waves do not fuse, but result in the formation of a deformed dinuclear system. The binding energy of neutrons is reduced while those for protons and α particles are enhanced in the deformed dinuclear system as compared to those in the shape-equilibrated system. Hence, the higher partial waves inhibit their contributions to the α-particle spectra and lead to the preshape equilibrium of neutrons and protons, with the neutron emission dominating over the proton emission.