The Contribution Of First Forbidden Transitions To Nuclearβ-Decay Half-Lives

β~--decay half-life is a key quantity for nuclear structure and astrophysical nucleosynthesis study,it can determine the location and path evolution of r-process in nuclear chart.Experimental data ofβ~--decay half-life for most neutron-rich nuclei including r-process nuclei are poor,which makes the actual site and exact path hard to determine.Experimental data ofβ~--decay half-life are studied systematically near waiting point N=126 and heavy nuclei(80<N<100)in this paper,in which the contribution of forbidden transition(FF)are considered.Brief overview to the two works as follows.Firstly,systematical studies on only experimental data ofβ~--decay half-life of nuclei near N=126,and utilize exponential formula proposed by Zhang et al.to fit these data.Through the fitting and analysis,the new parameters of the exponential formula near N=126 are determined.The proposed exponential formula including new parameters can include self-consistently the contribution of FF transition near N=126.The result indicates that the exponential formula including new parameters considering FF contribution is in good agreement with experimental data ofβ~--decay half-life of nuclei around N=126.Secondly,through systematical analysis on experimental data of FF contribution ofβ~--decay in the heavy nuclei(80<N<100)in this paper.The formula quantifying FF contribution is proposed firstly in this paper,it can produce reasonably the experimental data.Based on the formula,another formula of calculatingβ~--decay half-life including FF contribution is proposed further.The latter formula has 8parameters and produces the experimental data well.This result are significant for the exact input ofβ~--decay half-life in r-process.The FF contributions of 1373 nuclei calculated by the branching ratio formula are predicted for the nuclei zone(28<Z<75,50<N<126),the result is in agreement with the prediction calculated by Marketin et al.as a whole.This result is significant to study nuclear structure,balance the contributions of allowed and forbidden transitions and hence the quenching factor of the 8 matrix elements in the FF transitions.