Pramana – J. Phys. (2017) 88: 43 c Indian Academy of Sciences DOI 10.1007/s12043-016-1328-1 Alpha decay and cluster decay of some neutron-rich actinide nuclei G M CARMEL VIGILA BAI1 and R NITHYA AGNES2,∗ 1Department of Physics, Rani Anna Government College for Women, Tirunelveli 627 008, India 2Department of Physics, St. John’s College, Palayamkottai 627 002, India ∗Corresponding author. E-mail: [email protected] MS received 18 July 2015; revised 1 June 2016; accepted 20 July 2016; published online 9 February 2017 Abstract. Nuclei in the actinide region are good in exhibiting cluster radioactivity. In the present work, the half-lives of α-decay and heavy cluster emission from certain actinide nuclei have been calculated using cubic plus Yukawa plus exponential model (CYEM). Our model has a cubic potential for the overlapping region which is smoothly connected by a Yukawa plus exponential potential for the region after separation. The computed half-lives are compared with those of other theoretical models and are found to be in good agreement with each other. In this work, we have also studied the deformation effects on half-lives of cluster decay. These deformation effects lower the half-life values and it is also found that the neutron-rich parent nuclei slow down the cluster decay process. Geiger–Nuttal plots for various clusters are found to be linear and most of the emitted clusters are α-like nuclei. Keywords. Alpha decay; cluster radioactivity; spontaneous fission. PACS Nos 23.60.+e; 23.70.+j 1. Introduction nucleus along with that of the mitted cluster and daugh- ter nucleus using cubic plus Yukawa plus exponential The process of spontaneous emission of fragments model (CYEM). This region is a fertile region in exhi- heavier than α-particles but lighter than the lightest biting cluster radioactivity because most of the daughter fission fragment is known as cluster radioactivity. The- nuclei are the double magic nuclei or a neighbouring oretically, such emissions were first predicted by nucleus. In this model, the zero-point vibration energy Sandulescu et al [1]. The first experimental observation is explicitly used without violating the energy con- was made by Rose and Jones [2]. Two types of models servation and the inertial mass coefficient dependent exist in explaining the exotic decay process. One is the on the centre of mass distance. In §2 we have done preformed cluster model [3–5], in which the cluster our calculations by considering Coulomb plus Yukawa is assumed to be preborn in a parent nucleus before plus exponential potential as the interacting barrier for it penetrates the barrier. Another is the fission model separated fragments and the cubic potential for the [6–8], in which the nucleus deforms continuously as overlap region. The results and discussions are given it penetrates the nuclear interacting barrier and reaches in §3. Finally, the conclusions from our study are given scission configuration after running down the Coulomb in §4. barrier. Many theoretical models were developed to study 2. Cubic plus Yukawa plus exponential model the cluster radioactivity. The role of deformation effect on half-lives in cluster decay has been studied by In this work, the parent and the emitted cluster are many researchers using different theoretical models considered to be spheroid, keeping the daughter as [9–12]. In this paper, we have calculated the half-life spherical. If the emitted cluster has a deformation, of all the possible cluster emissions from the neutron- say quadrupole deformation only while the daughter rich actinide parent nuclei by including quadrupole nuclear is spherical and if the Q-value of the reaction and hexadecapole deformations of the decaying parent is taken as the origin, the potential for the post-scission 1 43 Page 2 of 7 Pramana – J. Phys. (2017) 88: 43 Table 1. Comparison of calculated values of logarithmic half-lives for α-decay of some actinide nuclei with deformation (WD) and without deformation (WOD). log T (s) Daughter Emitted Calculated Reference Decay −1 Parent nuclei cluster Q CYEM CYEM ELDM Expt. ASAFM constant (s ) nuclei Zd Ad Ze Ae (MeV) (WOD) (WD) [21] [22] [23] Calculated 232 −4 95Am 91 228 2 4 7.28 2.39 2.34 2.54 1.89 3.6 2.823 × 10 234 −5 95Am 91 230 2 4 6.88 3.99 3.90 4.13 – 5.6 7.091 × 10 235 −5 95Am 91 231 2 4 6.71 4.71 4.63 4.84 – 5.3 1.351 × 10 237 −8 95Am 91 233 2 4 6.19 7.13 7.02 7.24 7.18 7.2 5.137 × 10 238 −8 95Am 91 234 2 4 6.05 7.83 7.72 7.93 – 9.3 1.025 × 10 239 −9 95Am 91 235 2 4 5.92 8.50 8.36 8.55 – 8.7 2.192 × 10 240 −10 95Am 91 236 2 4 5.71 9.64 9.46 9.73 – 11.0 1.588 × 10 241 −11 95Am 91 237 2 4 5.64 10.02 9.82 10.09 10.13 10.2 6.618 × 10 242 −11 95Am 91 238 2 4 5.59 10.29 10.52 10.36 – 11.7 3.554 × 10 238 −7 96Cm 94 234 2 4 6.62 6.53 6.40 5.64 3.94 4.9 2.045 × 10 239 −7 96Cm 94 235 2 4 6.59 6.66 6.52 5.77 – 7.0 1.516 × 10 240 −8 96Cm 94 236 2 4 6.40 7.55 7.35 6.63 6.37 6.5 1.953 × 10 241 −9 96Cm 94 237 2 4 6.18 8.65 8.44 7.66 – 8.6 1.551 × 10 242 −9 96Cm 94 238 2 4 6.22 8.42 8.19 7.49 7.15 7.2 2.635 × 10 243 −9 96Cm 94 239 2 4 6.17 8.66 8.37 7.70 8.96 9.0 1.516 × 10 244 −11 96Cm 94 240 2 4 5.90 10.10 9.80 9.08 8.76 8.8 5.506 × 10 246 −13 96Cm 94 242 2 4 5.47 12.60 12.21 11.50 11.18 – 1.741 × 10 248 −15 96Cm 94 244 2 4 5.16 14.59 14.11 13.46 13.04 – 1.781 × 10 250 −15 96Cm 94 246 2 4 5.17 14.49 14.03 13.38 11.42 – 2.243 × 10 248 −9 98Cf 96 244 2 4 6.36 8.61 8.20 7.63 7.46 – 1.701 × 10 249 −9 98Cf 96 245 2 4 6.3 8.27 8.46 7.94 10.04 – 3.722 × 10 250 −10 98Cf 96 246 2 4 6.13 9.78 9.26 8.77 8.62 8.6 1.150 × 10 251 −10 98Cf 96 247 2 4 6.18 9.50 9.01 8.52 10.45 10.9 2.192 × 10 252 −10 98Cf 96 248 2 4 6.22 9.27 8.74 8.28 7.92 8.0 3.722 × 10 253 −10 98Cf 96 249 2 4 6.13 9.73 9.23 8.74 – 8.7 1.290 × 10 254 −11 98Cf 96 250 2 4 5.93 10.81 10.26 9.79 – 9.3 1.073 × 10 256 98Cf 96 252 2 4 5.56 12.97 12.39 11.90 – 11.6 7.4256 251 −9 99Es 97 247 2 4 6.60 7.87 7.39 6.92 – 7.4 9.348 × 10 252 −8 99Es 97 248 2 4 6.80 6.90 6.44 5.99 7.61 7.6 8.724 × 10 253 −8 99Es 97 249 2 4 6.74 7.16 6.66 6.23 6.25 6.2 4.794 × 10 254 −8 99Es 97 250 2 4 6.62 7.72 7.24 6.78 7.38 8.4 1.321 × 10 255 −9 99Es 97 251 2 4 6.44 8.59 8.07 7.62 – 7.6 1.781 × 10 256 −10 99Es 97 252 2 4 6.23 9.66 9.08 8.66 – 10.8 1.516 × 10 253 −4 101Md 99 249 2 4 7.71 3.94 3.42 3.11 – 3.2 4.081 × 10 254 −5 101Md 99 250 2 4 7.89 3.23 2.76 2.42 – 3.9 7.957 × 10 255 −4 101Md 99 251 2 4 7.91 3.13 2.64 2.33 3.21 2.4 5.137 × 10 256 −4 101Md 99 252 2 4 7.9 3.15 2.64 2.36 3.66 3.9 4.906 × 10 257 −5 101Md 99 253 2 4 7.56 4.46 3.93 3.60 4.30 3.7 2.403 × 10 258 −6 101Md 99 254 2 4 7.27 5.65 5.08 4.73 6.65 5.8 1.551 × 10 259 −7 101Md 99 255 2 4 7.11 6.32 5.72 5.39 – 6.1 3.317 × 10 260 −8 101Md 99 256 2 4 6.95 7.03 6.03 6.10 6.38 8.9 6.468 × 10 250 102No 100 246 2 4 8.96 0.03 −0.30 −0.65 −0.12 −1.2 0.6468 254 −3 102No 100 250 2 4 8.23 2.41 1.91 1.63 1.71 1.7 2.696 × 10 255 −2 102No 100 251 2 4 8.44 1.65 1.18 0.88 2.27 2.8 1.50 × 10 256 −2 102No 100 252 2 4 8.58 1.16 0.70 0.41 0.44 0.5 4.794 × 10 257 −2 102No 100 253 2 4 8.45 1.58 1.09 0.81 – 2.1 1.823 × 10 Pramana – J.