High Temperature Rotating Nuclear ~ (132) Of Nd ~ *, ~ (82) Of Sr ~ * Electric Dipole Giant Resonance Properties And ~ (82) Sr ~ * The Gdr Incident Channel Effects

Interesting information of hot rotating nuclei can be derived from theangular distributions and γ-ray spectra of the giant dipole resonance (GDR)photons. The measurement of the γ-ray spectra can give information aboutnuclear shape change, and the measurement of the angular distribution ofthe GDR photons Provides a complementary method for studying the GDRin hot nuclei that have an alignment due to rotation. It is a sensitive probeto detect the nuclear deformation. The value of angu1ar anisotropy a₂ (E_γ) asa driction of the y transition energy depends markedly on the orientation ofthe nucleus. It gives information on the shape and shape fluctuations of thenucleus and can be directly compared with theoretica1 analysis without anykind of pre-analysis using the staistical model. So far, the experimentalinformaton on high-energy γ-ray angular distribution from statistical decayis limited, only some isotopes have been studied systematicallyFurthermore, in the mass range A around 130, even the high-energy γ-rayspectra are very scarce. On the other hand, some superdeformed bands havebeen discovered recently in thes range. For examle, three neW wealdypOPulated rotational bands have been fOund, Which are believed to beassociated with a suPerdeformed Prolate ShaPe of l32Nd'. UP to thebeginning of our measurement, there are only some theoretical Predictionsof GDR bullt on suPerdeformed Staes (SDGDR), but no measurd data.K.S.Tanabe and YS.Chen had given their theoretical calcuaton forSDGDR: giant diPOle resonances built on suPerdeformed rotatonal staesand angular distributon of Yray from high-spin gian diPOle resonances onsuPerdefOrmed states. It is indicated tha there are SDGD in l32Nd' andsome othr nuclei When they wer excited to high enough sPin. So it is veryinteresting tO StUdy l32Nd* exPerirnentallyThe high-energY Y-rays sPectra and its angUlar distributons from thedeexcitaion of the gian dipole resonance have been measured frOm thedecay of compound nucleus l32Nd' formed by the 32S+looRu reaction at anincident Proectile eneng of 140 MeV of 32S. The y-ray multiPlicitydiStribution of thes reaction was detennind with a multiPlicity fiitercomPosed of 38 hexagonal BGO cryStals. The shaPe evolution of the l32Nd'has been Studied as a function of spin.The exPerimenta measuremot was performed at m-l3 tandem atCIAE. We measured the 100Ru (':S,Y) l32Nd' reaction at prOjectile energy of140 MeV after correction for the beam energy loss in the target. ThecorresPonding excitation energy E. of the comPound nucleus l32Nd' wasabout 62.8 MeV and itS average angUlar momeAn tranferred wasabout 30.4 h. The enriched (92.1%) looRu target was 2 mg/ cm2 with Pbbacking (20 mg/ cm2). High energy y-rays were detected wim twO largevo1ume and high efficiency NaI-plastic anicoincidence shieldedspectrOmaters, both located at ditrice of l mater from the target to thefrOn face of NaI deectOL The detector consistS of a NaI crystal (424 x 25.4and 420 x 20 cm, resPectvely) SUrrQUlld by a plastic anticoincideneshielding and a frOn detectOL The shielding detectors measur the room-scattering neUtrons and the backgrOUn y-rays. The tiIne-offligh (TOF)technique was adopted to reduce the nethen-induced backgrOund. The Startsignals of TOF were taken frOm the pick uP signals of the ns pulsed beam.. The time resofution was 2 ns fOr the Yrays above 5 MeV the energyresolution was 5% for l5. l MeV Yrays.For the inclusive measurment a staistical model analysis is based onthe results of the fits of the ealSting inclusive sPeCtra correSPonding noonly tO &ffernt excitaton energy E. but also differen SPin a)' To obtainthe small region in the plane ra.' I) in the measurment, a multiPlicty filterconsiSting of 38 hexagonal BGO wts was used tO detennin themultiplicity (mp distribuion. The 19 of 38 BGO crystals were located nearthe top of the mpt and another l9 near the bOttOm. The coincidene foldsof y-ray...