2College of Physics and Electronics,
3National Exemplary Base for International Sci & Tech. Collaboration of Nuclear Energy and Nuclear Safety,
4Cooperative Innovation Center for Nuclear Fuel Cycle Technology & Equipment,
5Key Laboratory of Low Dimensional Quantum Structures and Quantum Control,
First author contact:
Received:2020-12-10Revised:2021-04-12Accepted:2021-04-15Online:2021-05-20
Fund supported: |
Abstract
Keywords:
PDF (381KB)MetadataMetricsRelated articlesExportEndNote|Ris|BibtexFavorite
Cite this article
Xiao Pan(潘霄), You-Tian Zou(邹有 甜), Hong-Ming Liu(刘宏 铭), Biao He(何彪), Xiao-Hua Li(李小 华), Dong Xiang(向东). Released energy formula for proton radioactivity based on the liquid-drop model
1. Introduction
With the continuous developments of radioactive beam facilities, the study of exotic nuclei far from the β-stability line has became a hot project in nuclear physics field [1–9]. Exotic nuclei usually exhibit distinctive features that can provide a lot of information about the nuclear structure different from the well-known stable nuclei, such as new shell closures [10], coupling of bound state and unbound state and so on [11]. Proton radioactivity, the spontaneous emission of a proton by the nucleus, is an important decay mode of exotic nuclei. In 1970, this decay mode was firstly observed in an isomeric state of 53Co by Iackson et al [12, 13]. Subsequently, proton emissions from ground state of 151Lu [14] and147Tm [15] were detected by Hofmann et al and Klepper et al. Up to now, there are 44 proton emitters decaying from their ground states or isomeric states between Z = 51 and Z = 83 [11, 16–22] being identified in experiments.Proton radioactivity shares the similar theory of barrier penetration with different kinds of charged particles' radioactivity, such as α decay, heavy ion emission, spontaneous fission, etc [23–31]. Theoretically, a great deal of methods have been proposed to deal with proton radioactivity half-life, which can be divided into two categories. One kind is theoretical models that the probability of proton penetration barrier is calculated by the Wentzel–Kramers–Brillouin approximation, such as the unified fission model [32, 33], the single-folding model [17], the modified two-potential approach [20, 34], the Gamow-like model [35], the effective interactions of density-dependent M3Y [36–38], the generalized liquid-drop model [19, 28], the Coulomb and proximity potential model, etc [21, 39, 40]. The other one is empirical formulas, which rely on the accurate released energy Qp and orbital angular momentum l taken away by emitted proton, such as universal decay law for proton radioactivity [41], the formula of Zhang and Dong [1], the New Geiger–Nuttall law [42], etc. Using these formulas, ones can estimate the half-life of proton radioactivity easily and rapidly. However, without precise Qp, we can not to predict the half-life of proton radioactivity for the certain nuclei whose proton radioactivity is energetically allowed or observed but not yet quantified. Therefore, obtaining a simple and accurate Qp formula is very necessary. In 2010, based on the macroscopic-microscopic model, a simple and local formula for calculating α-decay energies of superheavy nuclei was proposed by Dong et al [43]. They used this formula to calculate the α-decay energy, the theoretical calculations can well reproduce the experimental data. Meanwhile, they also predicted the α-decay energy of newly synthesized superheavy nuclei and obtained positive results. Refering to the shell correction form obtained by Dong et al, we propose the Qp formula including the liquid-drop part and shell correction. The liquid-drop part is the main part of our formula, which is derived from the Bethe–Weizsäcker binding energy formula.
This article is organized as follows. In the next section, the formula of released energy for proton radioactivity is briefly described. The detailed calculations and discussion are presented in section
2. The formula of released energy for proton radioactivity
The relationship between the released energy of proton radioactivity and binding energy can be expressed as Qp = B(A − 1, Z − 1) − B(A, Z). If the change of binding energy with Z and A is relatively smooth, it can be replaced bySo, we can obtained the liquid-drop part of Qp formula as follows
However, simply considering the part of the liquid-drop in this formula, the Qp can only reflect the average trend of binding energy. While the effect of shell correction on the Qp is very important to nuclei around shell closures. Refering to the shell correction form for α-decay energies proposed by Dong et al, the final Qp formula is expressed as
3. Results and discussion
The Σ represents the deviation between the calculated value and experimental ones, in this work, which is defined as follows:At first, fitting the experimental data of Qp for 29 nuclei with proton radioactivity from ground state listed in table 1, we obtain the best parameters for equation (
Figure 1.
New window|Download| PPT slideFigure 1.The part (a) is the difference of proton radioactivity released energy between the calculated value and experimental one [42] using equation (
Table 1.
Table 1.The experimental data [42] and calculated results for 29 nuclei with proton radioactivity from ground state obtained by equation (
Nuclei | ${Q}_{p}^{\mathrm{Expt}.}$ (MeV) | ${Q}_{p}^{\mathrm{cal}.}$(MeV) | ΔQp(MeV) | Nuclei | ${Q}_{p}^{\mathrm{Expt}.}$ (MeV) | ${Q}_{p}^{\mathrm{cal}.}$(MeV) | ΔQp(MeV) |
---|---|---|---|---|---|---|---|
109I | 0.830 | 0.683 | −0.147 | 151Lu | 1.255 | 1.149 | −0.106 |
112Cs | 0.830 | 1.040 | 0.210 | 155Ta | 1.466 | 1.338 | −0.127 |
113Cs | 0.981 | 0.830 | −0.151 | 156Ta | 1.036 | 1.190 | 0.154 |
117La | 0.823 | 0.981 | 0.158 | 157Ta | 0.956 | 1.039 | 0.083 |
121Pr | 0.901 | 1.135 | 0.234 | 159Re | 1.816 | 1.527 | −0.289 |
130Eu | 1.043 | 1.271 | 0.228 | 160Re | 1.286 | 1.382 | 0.096 |
131Eu | 0.963 | 1.090 | 0.127 | 161Re | 1.216 | 1.235 | 0.019 |
135Tb | 1.193 | 1.260 | 0.067 | 164Ir | 1.844 | 1.575 | −0.269 |
140Ho | 1.106 | 1.266 | 0.160 | 166Ir | 1.177 | 1.291 | 0.114 |
141Ho | 1.190 | 1.098 | −0.092 | 167Ir | 1.087 | 1.149 | 0.062 |
144Tm | 1.725 | 1.443 | −0.282 | 170Au | 1.487 | 1.489 | 0.001 |
145Tm | 1.754 | 1.753 | −0.001 | 171Au | 1.464 | 1.350 | −0.115 |
146Tm | 0.904 | 1.121 | 0.216 | 176Tl | 1.278 | 1.418 | 0.140 |
147Tm | 1.133 | 0.959 | −0.174 | 177Tl | 1.172 | 1.284 | 0.112 |
150Lu | 1.283 | 1.306 | 0.023 |
New window|CSV
In the following, fixed the parameters a1 to a5 as mentioned above and let N0 in the equation (
Finally, as an application, we extend this formula to calculate 51 proton radioactivity candidates in region 51 ≤ Z ≤ 83 taken from the latest evaluated atomic mass table AME2016 [44, 45]. For comparison, the Qp are also evaluated using Weizsäcker–Skyrme (WS4) formula [46] and Hartree–Fock–Bogoliubov (HFB-29) model [47] In these two models, the Qp is calculated by [21]
The detailed results are given in table 2. In this table, the first five columns represent the proton emitter, the experimental data and the calculated Qp obtained by this work, WS4 and HFB-29, respectively. The last three column are the difference of Qp between the experimental data and calculated value derived by the three models mentioned above, denoted as Δ1, Δ2, Δ3. From this table, it indicates that all of the Qp in this work are positive, while in WS4 or HFB-29 the Qp of some nuclei such as 119La, 129Pm , 145Ho, 154,155 Lu, 171Ir , 177Au are negative. To obtain further insight into the well of agreement and the systematics of results, we plot the difference of Qp between the experimental data and calculated value using these three models in figure 2. From this figure, we can clearly see that the best result is WS4 to reproduce the experimental data but the worst is HFB-29 in these three models. The evaluation abilityour of our work is between them. Furthermore, we calculate the standard deviation between experimental Qp and calculated ones for this work, WS4 and HFB-29 are 0.347, 0.231 and 0.482 MeV, respectively. The reason may be that this work and WS4 are considered the effect of shell correction, but WS4 considers more comprehensively. Due to the uncertainty of skyme force and the pairing force that its corresponding parameters are obtained by fitting the properties of less nuclei and then extend it to the unknown regions, the results of Qp calculated by the HFB-29 model are inferior to the first two models.
Figure 2.
New window|Download| PPT slideFigure 2.The difference of Qp between the experimental data and calculated value for this work, WS4 and HBF-29.
Table 2.
Table 2.The experimental data and calculated Qp values of this work, the WS4 model and the HFB-29 model. Δ1, Δ2 and Δ3 are the deviation between experimental data and calculated value for equation (
Nuclei | Qp(MeV) | Δ(MeV) | |||||
---|---|---|---|---|---|---|---|
Expt. | This work | WS4 [46] | HFB-29 [47] | Δ1 | Δ2 | Δ3 | |
103 Sb | 1.469 | 0.984 | 1.389 | 1.729 | 0.485 | 0.080 | −0.260 |
104 Sb | 0.519 | 0.763 | 0.787 | 0.779 | −0.244 | −0.268 | −0.260 |
107 I | 1.510 | 1.113 | 1.965 | 1.940 | 0.397 | −0.455 | −0.430 |
108 I | 0.610 | 0.900 | 1.298 | 1.070 | −0.29 | −0.688 | −0.460 |
111 Cs | 1.820 | 1.246 | 1.927 | 2.220 | 0.574 | −0.107 | −0.400 |
114 Cs | 0.244 | 0.629 | 0.423 | 0.360 | −0.385 | −0.179 | −0.116 |
115 Cs | 0.106 | 0.423 | 0.181 | 0.060 | −0.317 | −0.075 | 0.046 |
116 La | 1.091 | 1.184 | 1.412 | 1.601 | −0.093 | −0.321 | −0.510 |
119 La | 0.281 | 0.588 | 0.093 | −0.139 | −0.307 | 0.188 | 0.420 |
123 Pr | 0.361 | 0.754 | 0.221 | 0.361 | −0.393 | 0.140 | 0.000 |
127 Pm | 0.922 | 0.921 | 0.828 | 0.342 | 0.001 | 0.094 | 0.580 |
128 Pm | 0.472 | 0.741 | 0.304 | 0.082 | −0.269 | 0.168 | 0.390 |
129 Pm | 0.152 | 0.558 | 0.140 | −0.448 | −0.406 | 0.012 | 0.600 |
131 Eu | 0.963 | 1.090 | 1.155 | 1.133 | −0.127 | −0.192 | −0.170 |
133 Eu | 0.563 | 0.737 | 0.441 | 0.583 | −0.174 | 0.122 | −0.020 |
137 Tb | 0.843 | 0.917 | 0.774 | 0.703 | −0.074 | 0.069 | 0.140 |
142Ho | 0.854 | 0.935 | 0.692 | 0.464 | −0.081 | 0.162 | 0.390 |
143 Ho | 0.794 | 1.244 | 0.542 | 0.294 | −0.45 | 0.252 | 0.500 |
144 Ho | 0.283 | 0.610 | 0.048 | 0.134 | −0.327 | 0.235 | 0.149 |
145 Ho | 0.174 | 0.447 | −0.218 | −0.186 | −0.273 | 0.392 | 0.360 |
148 Tm | 0.569 | 0.803 | 0.268 | 0.774 | −0.234 | 0.301 | −0.205 |
149 Tm | 0.323 | 0.645 | 0.163 | 0.824 | −0.322 | 0.160 | −0.501 |
152 Lu | 0.845 | 0.997 | 0.679 | 1.005 | −0.152 | 0.166 | −0.160 |
153 Lu | 0.625 | 0.842 | 0.460 | 0.485 | −0.217 | 0.165 | 0.140 |
154 Lu | 0.215 | 0.692 | −0.007 | 2.005 | −0.477 | 0.222 | −1.790 |
155 Lu | 0.112 | 0.539 | −0.089 | 0.035 | −0.427 | 0.201 | 0.077 |
158 Ta | 0.456 | 0.892 | 0.254 | 0.286 | −0.436 | 0.202 | 0.170 |
159 Ta | 0.389 | 0.743 | 0.141 | 0.316 | −0.354 | 0.248 | 0.073 |
165 Ir | 1.557 | 1.430 | 1.636 | 1.087 | 0.127 | −0.079 | 0.470 |
168 Ir | 0.557 | 1.011 | 0.721 | 0.237 | −0.454 | −0.164 | 0.320 |
169 Ir | 0.628 | 0.870 | 0.673 | 0.217 | −0.242 | −0.045 | 0.411 |
170 Ir | 0.090 | 0.734 | 0.260 | 0.067 | −0.644 | −0.170 | 0.023 |
171 Ir | 0.243 | 0.596 | 0.249 | −0.353 | −0.353 | −0.006 | 0.596 |
169 Au | 1.948 | 1.626 | 2.011 | 1.428 | 0.322 | −0.063 | 0.520 |
173 Au | 1.003 | 1.078 | 1.028 | 0.608 | −0.075 | −0.025 | 0.395 |
175 Au | 0.646 | 0.809 | 0.673 | 0.508 | −0.163 | −0.027 | 0.138 |
177 Au | 0.117 | 0.544 | 0.152 | −0.412 | −0.427 | −0.035 | 0.529 |
178 Tl | 0.718 | 1.154 | 0.963 | 1.388 | −0.436 | −0.245 | −0.670 |
179 Tl | 0.774 | 1.021 | 1.080 | 0.708 | −0.247 | −0.306 | 0.066 |
180 Tl | 0.266 | 0.892 | 0.677 | 0.308 | −0.626 | −0.411 | −0.042 |
181 Tl | 0.179 | 0.762 | 0.677 | 0.258 | −0.583 | −0.498 | −0.079 |
182 Tl | 0.061 | 0.634 | 0.182 | −0.062 | −0.573 | −0.121 | 0.123 |
184 Bi | 1.364 | 1.106 | 1.519 | 0.669 | 0.258 | −0.155 | 0.695 |
186 Bi | 1.124 | 0.853 | 0.938 | 0.259 | 0.271 | 0.186 | 0.865 |
187 Bi | 1.028 | 0.726 | 0.845 | 0.159 | 0.302 | 0.183 | 0.869 |
188 Bi | 0.521 | 0.603 | 0.300 | −0.311 | −0.082 | 0.221 | 0.832 |
189 Bi | 0.479 | 0.478 | 0.266 | −0.571 | 0.001 | 0.213 | 1.050 |
162 Re | 0.786 | 1.092 | 0.616 | 0.896 | −0.306 | 0.170 | −0.110 |
163 Re | 0.723 | 0.946 | 0.556 | 0.536 | −0.223 | 0.167 | 0.187 |
164 Re | 0.166 | 0.805 | 0.083 | 0.286 | −0.639 | 0.083 | −0.120 |
165 Re | 0.302 | 0.662 | −0.005 | 0.146 | −0.36 | 0.307 | 0.156 |
New window|CSV
4. Summary
In summary, based on the liquid-drop model and considered shell correction, we put forward a simple formula for the Qp. The corresponding parameters are obtained by fitting the experimental data of 29 nuclei with proton radioactivity from ground state. The standard deviation between the theoretical values and experimental ones is 0.157 MeV. In order to further test the reliability of this formula,we calculate the Qp values of 51 proton radioactivity candidates in region 51 ≤ Z ≤ 83 obtained from the latest evaluated atomic mass table AME2016 and compare with the Qp values extracted from the WS4 and HFB-29 models. It is found that the accuracy of our formula is higher than that of the HFB-29 model, although its accuracy is lower than that of the WS4 model. This indicates our formula is suitable for the predictions of Qp to some extent.Reference By original order
By published year
By cited within times
By Impact factor
DOI:10.1088/1674-1137/42/1/014104 [Cited within: 2]
DOI:10.1088/1674-1137/41/11/114104
DOI:10.1103/PhysRevC.101.014301
DOI:10.1103/PhysRevLett.89.102501
DOI:10.1016/S0146-6410(00)90013-9
DOI:10.1088/1674-1137/44/9/094106
DOI:10.1103/PhysRevC.58.220
DOI:10.1103/PhysRevC.95.014302
DOI:10.1088/1674-1137/abe10f [Cited within: 1]
DOI:10.1038/nature12226 [Cited within: 1]
DOI:10.1006/ndsh.2002.0001 [Cited within: 2]
DOI:10.1016/0370-2693(70)90269-8 [Cited within: 1]
DOI:10.1016/0370-2693(70)90270-4 [Cited within: 1]
DOI:10.1007/BF01415018 [Cited within: 1]
DOI:10.1007/BF01415019 [Cited within: 1]
DOI:10.1103/PhysRevLett.96.072501 [Cited within: 1]
DOI:10.1103/PhysRevC.72.051601 [Cited within: 1]
DOI:10.1016/j.ppnp.2007.12.001
DOI:10.1088/0954-3899/37/8/085107 [Cited within: 1]
DOI:10.1140/epja/i2016-16068-3 [Cited within: 1]
DOI:10.1103/PhysRevC.96.034619 [Cited within: 2]
DOI:10.1140/epja/i2017-12352-0 [Cited within: 1]
DOI:10.1088/0954-3899/17/6/001 [Cited within: 1]
DOI:10.1103/PhysRevC.80.024310
DOI:10.1103/PhysRevC.83.014601
DOI:10.1016/j.nuclphysa.2012.04.001
DOI:10.1088/0954-3899/42/8/085101
DOI:10.1103/PhysRevC.79.054330 [Cited within: 1]
DOI:10.1103/PhysRevC.92.064301
DOI:10.1016/0370-2693(79)90772-X
DOI:10.1088/1674-1137/abe112 [Cited within: 1]
DOI:10.1103/PhysRevC.71.014603 [Cited within: 1]
DOI:10.1088/1674-1137/34/2/005 [Cited within: 1]
DOI:10.11804/NuclPhysRev.35.04.470 [Cited within: 1]
DOI:10.1140/epja/i2016-16323-7 [Cited within: 1]
DOI:0.1088/0256-307X/27/7/072301 [Cited within: 1]
DOI:10.1016/j.physletb.2007.06.012
DOI:10.1088/0954-3899/30/6/B01 [Cited within: 1]
DOI:10.1016/j.nuclphysa.2012.10.003 [Cited within: 1]
DOI:10.1140/epja/i2019-12728-0 [Cited within: 1]
DOI:10.1103/PhysRevC.85.011303 [Cited within: 1]
DOI:10.1140/epja/i2019-12927-7 [Cited within: 3]
DOI:10.1103/PhysRevC.82.034320 [Cited within: 1]
DOI:10.1088/1674-1137/41/3/030002 [Cited within: 1]
DOI:10.1088/1674-1137/41/3/030003 [Cited within: 1]
DOI:10.1016/j.physletb.2014.05.049 [Cited within: 2]
DOI:10.1016/j.nuclphysa.2014.09.045 [Cited within: 2]
DOI:10.1103/PhysRevC.72.064613 [Cited within: 1]
DOI:10.1016/0092-640X(76)90027-9 [Cited within: 1]