The Study Of Nuclear Properties Via Photons Emitted In Intermediate Energy Heavy-ion Collisions

In this thesis,the study of nuclear properties via photons emitted in intermedi-ate energy heavy-ion collisions is performed,including giant dipole resonance(GDR)as a probe of deformed nuclei and energetic photons as a probe of the nuclear liquid-gas phase transition and collective flows in intermediate energy heavy-ion collisions,respectively.Firstly,the correlations between the GDR spectra and deformation parameters in the chains of Sm(A=134-154)and Nd(A=130-150)isotopes are investigated in the framework of an extended quantum molecular dynamics(EQMD)model.The calcula-tions of GDR spectra are well consistent with the experimental data,which confirms the reliability of the model and method for GDR.Meanwhile,the GDR spectra for several nuclei,i.e.134,136,138Sm and 130,132,134Nd,are also predicted.Then the mass number dependences of the resonance peak position(Em)in the major and minor axis direc-tions as well as the difference between two axes(?Em)are calculated.It is found that the Em and ?Em are extremely sensitive to the deformation of nucleus.Therefore,a quantitative study of the correlation between ?Em/(?)m and deformation parameter ? is performed.We have obtained ?Em/Em=0.69402?-0.00869 for the chain of Sm iso-topes and ?Em/Em=0.53845?-0.02872 for the chain of Nd isotopes.Additionally,the symmetry energy coefficient(Esym)dependence of GDR spectrum of 150Nd is also discussed.It is found that the calculated GDR spectrum in the EQMD model is perfectly consistent with the experimental results when Esym equals 32 MeV.Secondly,a systematic study of the multiplicities of energetic photons and inter-mediate mass fragments(IMFs)as well as its correlation between them in the reaction of 40Ca+40Ca is performed in a framework of an isospin dependent quantum molecular dynamics(IQMD)model.An incoherent neutron-proton bremsstrahlung photon pro-duction channel is embedded into the IQMD model.Comparison with the experimental results in the reaction of 14N+12C at incident energies of 20,30,40MeV/nucleon,it is found that the IQMD model with the in-medium nucleon-nucleon cross section(in-medium NNCS)can reproduce previous experimental data of energetic photon energy spectra better which also confirms the reliability of the model and method for energetic photons.Therefore,the incident energy and centrality dependences of the multiplicity of hard photons and IMFs as well as its correlation between them are investigated in the IQMD model with the in-medium NNCS.It is found that the multiplicities of thermal photons and IMFs as well as its correlation between them can provide valuable infor-mation on nuclear liquid-gas phase transition.All of them indicate that there occurs a nuclear liquid-gas phase transition state in the reaction of 40Ca+40Ca@70MeV/nucleon in the centrality of 0%?20%.In addition,the thermometer of thermal photons is also taken into account.We obtained that the temperature extracted from the inverse slope parameters of thermal photon spectra varies from 4.6MeV to 5.3MeV,which is consis-tent with other experimental and theoretic resultsFinally,the azimuthal anisotropy and multiplicities of both energetic photons and free nucleons in intermediate-energy heavy-ion collisions are investigated for 40Ca+40Ca collisions in the IQMD model with the in-medium NNCS.The studies of the average in-plane transverse momentum<px>distribution with the rapidity of particles in the center-of-mass frame and azimuthal distribution of both energetic photons and free nu-cleons indicate that thermal photons emitted in intermediate-energy heavy-ion collisions have the behaviors of directed and elliptic flows,which is for the first time to confirm thermal photons existing the anisotropic flow.Then the transverse momentum,cen-trality,and incident energy dependences of directed flow v1 and elliptic flow v2 are also studied.It is found that direct photons are stemmed from a repulsive mean field However,thermal photons and free nucleons are dominated by an attractive mean field So they have different emitting sources.Meanwhile,we also found that direct photons prefer to be emitted from out-of-plane while both thermal photons and free nucleons demonstrate in-plane emission enhancement.The above results indicate that there is an anti-correlation of v1 and v2 between direct photons and free nucleons,and a positive correlation between thermal photons and free nucleons.In addition,the multiplicity correlation between energetic photons and free nucleons is also calculated.The results show that there is a weak positive correlation between direct photons and free nucleons However,the anti-correlation between thermal photons and free nucleons is much more stronger.The result also shows that the reaction system of 40Ca+40Ca@70MeV/nucleon in the centrality of 0%?20%may occur a liquid-gas phase transition.