Srijit Bhattacharya

Coherent bremsstrahlung and GDR width from 252Cf cold fission

Abstract The energy spectrum of the high energy γ-rays in coincidence with the prompt γ-rays has been measured for the spontaneous fission of 252Cf. The nucleus–nucleus coherent bremsstrahlung of the accelerating fission fragments is observed and the result has been substantiated with a theoretical calculation based on the Coulomb acceleration model. The width of the giant dipole resonance (GDR) decay from the excited fission fragments has been extracted for the first time and compared with the thermal shape fluctuation model (TSFM) in the liquid drop formalism. The extracted GDR width is significantly smaller than the predictions of TSFM.

Extreme nuclear shapes examined via giant dipole resonance lineshapes in hot light-mass systems

The influence of alpha clustering on nuclear reaction dynamics is investigated using the giant dipole resonance (GDR) lineshape studies in the reactions {sup 20}Ne (E{sub lab}=145,160 MeV) + {sup 12}C and {sup 20}Ne (E{sub lab}=160 MeV) + {sup 27}Al, populating {sup 32}S and {sup 47}V, respectively. The GDR lineshapes from the two systems are remarkably different from each other. Whereas, the non-alpha-like {sup 47}V undergoes Jacobi shape transition and matches exceptionally well with the theoretical GDR lineshape estimated under the framework rotating liquid drop model (RLDM) and thermal shape fluctuation model (TSFM) signifying shape equilibration, for the alpha cluster {sup 32}S an extended prolate kind of shape is observed. This unusual deformation, seen directly via gamma decay for the first time, is predicted to be due to the formation of orbiting dinuclear configuration or molecular structure of {sup 16}O + {sup 16}O in the {sup 32}S superdeformed band.

Characterization of fragment emission inNe20(7–10 MeV/nucleon)+C12reactions

The inclusive energy distributions of the complex fragments (3{<=}Z{<=}7) emitted from the bombardment of {sup 12}C by {sup 20}Ne beams with incident energies between 145 and 200 MeV have been measured in the angular range 10 deg.{<=}{theta}{sub lab}{<=}50 deg. Damped fragment yields in all the cases have been found to have the characteristic of emission from fully energy equilibrated composites. The binary fragment yields are compared with the standard statistical model predictions. Whereas Li and Be fragments yields are in agreement with statistical-model calculations, enhanced yields of entrance channel fragments (5{<=}Z{<=}7) indicate the survival of orbiting-like process in {sup 20}Ne+{sup 12}C system at these energies.

Scaling of the giant dipole resonance widths in hot rotating nuclei from the ground state values

The system atics ofthe giant dipole resonance (GDR) widths in hot and rotating nucleiare studied in term softem peratureT,angularm om entum J and m assA.Thedierentexperim ental datain thetem peraturerangeof1-2M eV havebeen com pared with thetherm alshapeuctuation m odel(TSFM ) in the liquid drop form alism using a m odied approach to estim ate the average values ofT,J and A in the decay ofthe com pound nucleus. The values ofthe ground state GDR widthshave been extracted from theTSFM param etrization in theliquid drop lim itforthe corrected T,Jand A foragiven system and com pared with thecorrespondingavailablesystem atics ofthe experim entally m easured ground state GDR widthsfor a range ofnucleifrom A = 45 to 194. Am azingly, the nature of the theoretically extracted ground state GDR widths m atches rem arkably well,though 1.5 tim essm aller,with the experim entally m easured ground state GDR widthsconsistently overa widerangeofnuclei.

Giant dipole resonance width as a probe for nuclear deformation at finite excitation

The first systematic study of the correlation between the experimental giant dipole resonance (GDR) width and the average deformation � β� of the nucleus at finite excitation is presented for the mass region A ∼ 59 to 208. We show that the width of the GDR (� ) and the quadrupole deformation of the nucleus do not follow a linear relation, as predicted earlier, owing to the GDR-induced quadrupole moment, and the correlation also depends on the mass of the nuclei. The different empirical values of � β� extracted from the experimental GDR width match exceptionally well with the thermal shape fluctuation model. As a result, this universal correlation between

Onset of deformation at N = 112 in Bi nuclei

Ne,6n) fusion evaporation reaction at 130 MeV. The γγ coincidence data were taken using an array of 8clover HPGe detectors. The spin and parity assignments of the excited states have been made fromthe measured directional correlation from oriented states (DCO) ratios and integrated polarizationasymmetry (IPDCO) ratios. The results show, for the first time, the evidence of a rotational likeband based on a 13/2

Signature of clustering in quantum many-body systems probed by the giant dipole resonance

The present experimental study illustrates how large deformations attained by nuclei due to cluster formation are perceived through the giant dipole resonance (GDR) strength function. The high energy GDR

Study of dissipative collisions of 20Ne (≈7-11 MeV/nucleon) + 27Al

\gamma

CLUSTER EMISSION IN 13C + 12C and 12C + 12C REACTIONS AT ~ 6 MEV/NUCLEON

-rays have been measured from

Study of dissipative collisions of {sup 20}Ne (MeV/{approx_equal}7-11 nucleon)+ {sup 27}Al

^{32}