Excited State Of Halo Nuclei To Find And The Nature Of The Halo Nucleus

Angular distributions for some interesting states of 12B and 13C have been experimentally measured in HB(d,p) and 12C(d,p) reactions. The density distributions,RMS (Root Mean Square) radii,contributions of outside nucleon,etc.,of the valence neutrons in these states are extracted by DWBA (Distorted Wave Born Approximation) method and ANC (Asymptotic Normalization Coefficient) method,respectively. Additionally,the comparison between these two methods is made. Due to the approximate model-independence of ANC method,the final results are adopt the values given by the ANC method. The ANCs are 1.93+0.17 fin-1/2,1.84+0.16 fm-1/2 and 0.15+0.01 fm-1/2;RMS radii are 3.39+0.31 fin,5.04+0.75 fin and 3.68+0.40 fin;and the probabilities of valence neutrons outside the potentials are 14.3%,50.3% and 25.2% for the ground state,the first and third excited states of 13C,respectively. The results make sure that the first excited state of 13C is the one-neutron halo state. This is the first time to experimentally confirm that the excited halo state can exist on the p stable line. Meanwhile,the ANCs are 1.16+0.10 fin-1/2,1.34+0.12 fm-1/2 and 0.94+0.08 fm-1/2;RMS radii are 3.16+0.32 fm,4.01+0.61 fin and 5.64+0.90 fin;and the probabilities of valence neutrons outside the potentials are 19.9%,53.6% and 66.8% for the ground state,the second and third excited states of 12B,respectively. The results show that the second and third excited states of 12B are one-neutron halo states. It is the second nucleus to be found with new halo states near the p stable line.Using the ANCs of the 2s 1/2 states given by the (d,p) reactions,the radioactive capture cross sections of uB(n,Y)'2B and 12C(n,y)'3C,of which are interesting in the astrophysics are calculated. The calculation results are good in agreement with the experimental ones for the 12C(n,y)13C reaction. It is proved that such ANC method works perfectly. Due to the difficulty in the direct measurement,it is important to calculate these cross sections by the indirect ANC method. The values of these cross sections affect the path to synthesize the A > 12 elements.Through the experimental work of this thesis,the single-particle potential model is comprehended and some improvements are made. Utilizing this model,the distributions of valence nucleons are calculated for some light nuclei. Some new halo or skin states are predicted. Moreover,the calculations of the valence neutrons for the single-particle states of 49Ca and 209Pb show that the neutron halos or skins can exist in the region of heavy nuclei. Search for these nuclear states is one of our tasks in thefuture. Furthermore,according to the results of the single-particle potential model,the more natural necessary condition for the formation of the halo structure is given with the Woods-Saxon potential. This condition is more loser than the current one. The necessary condition of proton halo occurrence is first time given out and the existence region is pointed out. All of these have realistic meaning for searching the new halo or skin nuclear states.In addition,some interesting questions are discussed in this thesis,for example,the effect of the configuration of nucleon on the density distributions,the sequence overturn between the 2s1/2 and 1d5/2 energy levels when the neutron halo exists,the existence of the proton halo nucleus,and the appearance of new magic number (N=16) under the weak bounded condition,etc..Anyway,halo is a charming phenomenon,waiting for us to discover it.