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Decay Modes of Uranium in the Range 203 <A<299

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Decay Modes of Uranium in the Range 203 <A<299 Indian Journal of Pure & Applied Physics Vol. 58, April 2020, pp. 234-240 Decay modes of Uranium in the range 203 <A<299 H C Manjunathaa*, G R Sridharb,c, P S Damodara Guptab, K N Sridharb, M G Srinivasd & H B Ramalingame aDepartment of Physics, Government College for Women, Kolar 563 101, India bDepartment of Physics, Government First Grade College, Kolar 563 101, India cResearch and Development Centre, Bharathiar University, Coimbatore 641 046, India dDepartment of Physics, Government First Grade College, Mulbagal 563 131, India eDepartment of Physics, Government Arts College, Udumalpet 642 126, India Received 17 February 2020 In the present work, we have considered the total potential as the sum of the coulomb and proximity potential. We have used the recent proximity function to calculate the nuclear potential. The calculated logarithmic half-lives correspond to fission, cluster and alpha decay are compared with that of experiments. We also identified the most probable decay mode by studying branching ratios of these different decay modes. The competition between different decay modes such as fission, cluster radioactivity and alpha decay finds an important role in nuclear structure. Keywords: Nuclear potential, Cluster radioactivity, Alpha decay, Spontaneous fission 1 Introduction Parkhomenko et al.18 studied the alpha decay It is important to study the alpha decay properties properties for odd mass number superheavy nuclei. of superheavy nuclei. Most of the superheavy nuclei Poenaru et al.19 improved the formula for alpha decay are identified through alpha decay process only. halflives around magic numbers by using the SemFIS Many researchers in the nuclear physics field formula. Sobiczewski et al. 20 reviewed the theoretical predicted alpha decay half-lives for the superheavy studies on alpha decay of superheavy nuclei, which nuclei1-10. Superheavy nuclei can be synthesized using are based on both traditional macroscopic– fusion reaction through the compound nucleus microscopic, and purely microscopic and self- formation. The compound nucleus formed during the consistent approaches. fusion reaction undergoes different decay modes such Ni et al.21 proposed a general formula of half-lives as alpha decay, spontaneous fission and cluster for α decay and cluster radioactivity. Poenaru et al.22-24 radioactivity, etc. It is important to study the formulated the expression for half-lives of heavy- competition between different decay modes. particle radioactivity (HPR) and alpha decay using the 11 Manjunatha and Sowmya studied the competition WKB approximation. Poenaru et al.25,26 studied the between spontaneous fission, ternary fission, cluster alpha decay half-lives and cluster radioactivity of decay and alpha decay in the super heavy nuclei of superheavy nuclei. A study of alpha and cluster decay Z=126. It finds importance to construct a simple and is important to predict the decay mode of superheavy accurate semi empirical formula for the prediction of nuclei27,28. Hourani29 measured the cluster alpha decay and cluster radioactivity. Earlier radioactivity in heavy elements. Nuclei in the actinide researchers proposed different formulae for the region are unstable and exhibiting alpha, cluster 12-15 16 evaluation of alpha decay half lives . Poenaru radioactivity and spontaneous fission. Heavy nuclei et al. evaluated the deviations of the formulae may decay through the different decay modes such as 13-15 17 proposed by the earlier workers . Earlier workers spontaneous fission, cluster and alpha decay. We have shown that preformed-cluster models are equivalent studied the different decay modes such as cluster, with fission models, used to describe in a unified alpha decay, β- decay, β+ decay and spontaneous way cluster radio activities and alpha decay. fission of Uranium in the range 203 <A<299. The aim —————— of present work is also to identify the prominent *Corresponding author (E-mail: [email protected]) decay modes of uranium in the range 203 <A<299. MANJUNATHA et al.: DECAY MODES OF URANIUM 235 2 Theory where RC 1.24(R1 R2 ) R1 and R2 are the radii of , 2.1 Cluster radioactivity and alpha decay process the emitted alpha/cluster and daughter nuclei, The interacting potential between two nuclei is the respectively. Z1 and Z2 are the atomic numbers of the sum of the Coulomb potential and proximity potential. daughter and emitted cluster. We have used the We have used Denisov nuclear potential Vp(r)30 to study proximity function defined specially for cluster/alpha the binary and ternary fission, is given by decay and it is given by31 R R 1 2 p1 VP(r) 1.989843 φ(r R1 R2 2.65) Φ(ε) with R1 R2 s p 1 exp 0 2 3/2 A1 A2 p3 1 0.003525139 0.4113263(I1 I2 ) A2 A1 R R R s 1 2 0 … (5) … (1) b Where effective nuclear radius is given by Previous researchers evaluated the proximity function for the density-dependent nucleon-nucleon 11.65415 0.4A interaction using the double folding model and fitted i Ri Rip 1 1.284589 Ii (i 1,2) Rip Ai 200 the equation for the evaluated proximity function values. The fitting parameters p1, p2 and p3 defined by … (2) 32 the previous researchers are -7.65, 1.02 and 0.89, Where Rip is given by respectively. For all the four decays such as spontaneous fission, 1.646 A 2Z 3/2 i i alpha ternary fission, cluster decay and alpha decay, Rip 1.24Ai 1 0.191 with Ai Ai the barrier penetrability P is given as: N Z i i b Ii … (3) 2 Ai P exp 2(V Q)dz … (6) a The universal function ф(s=r-R1-R2-2.65) is given by Here mA1 A2 A , where m is the nucleon mass and A , A are the mass numbers of daughter and 1 s/0.788166 3 1.229218S 2 0.2234277S 3 1 2 emitted clusters, respectively. The equation, 0.1038769S 4 V (a) V (b) Q gives the turning points ―a‖ and R1R 2 2 3 ―b‖ for cluster/alpha decay. For fission process, first 0.1844935S 0.07570101 S I1 I2 R1 R 2 turning point is determined from the equation V(a)=Q 2 3 and second turning point b=0. The above integral can Φ(ξ) 0.04470645 S 0.03346870 S for - 5.65 S 0 be evaluated numerically or analytically, and the half- 2 R1R 2 S life time is given by: 1 S 0.05410106 exp R1 R 2 1.760580 ln 2 ln 2 S S T1 2 … (7) 0.5395420 I1 I2 exp exp P 2.424408 0.7881663 2E for S 0 where represent the number of assaults 2 h We have used Coulomb potential Vc(R), to study the on the barrier per second and λ the decay constant. Ev, cluster decay and alpha decay, is given by: the empirical vibration energy, is given as: 1 (R > RC ) R … (4) 4 A2 2 V (R) Z Z e 2 Eυ Q0.056 0.039exp for A2 4 C 1 2 1 R 2.5 3 (R RC ) 2Rc Rc … (8) 236 INDIAN J PURE APPL PHYS, VOL. 58, APRIL 2020 2.2 Proton emission half-lives 2.5 β+ decay formula We have evaluated the proton decay half-lives Zhang et al.40 proposed semi empirical formula for using expression given by the previous researcher33: β+ decay and it is expressed as: 1 1 1 p p 6 2 2 2 4 logT a bA Z cZQ d d log10T1 2 c1Z c2 N c3Z c4 1/ 2 2 2 4 4 … (13) … (9) Z and N are the proton and neutron number, where Z and A are charge and mass number of parent respectively. The parameters c1, c2, c3 and c4 are nucleus, respectively. Where a, b, c, d2, p2, d4 and p4 different for different orders. The first and second 33 + are constants . β2 and β4 are quadrupole and forbidden transition for β decay and the different hexadecapole deformation parameters. parameters are explained in detail36. The even-odd effects are also considered in the above equation. 2.3 Spontaneous fission The generalised spontaneous fission including 3 Results and Discussion pairing, shell model calculations and valence The amount of energy released during distinct nucleons, Ren et al.34 constructed a semi-empirical fission process is studied from the following equation: formula for spontaneous fission half-lives and is given by: n Q M (A,Z) M (A ,Z ) … (14) Z 90 Z 90 2 i i log T yr 21.08 c c i 10 1 2 1 A 2 A 3 where ΔM(A, Z) and ΔM(Ai,Zi) are mass excess of the Z 90 Z 90 2 c3 c4 N Z 52 parent and daughter nuclei respectively. These mass A A excess values are taken from 37-42. The variation of … (10) energy released (Q) in different decay modes (cluster where c 548.825021 , c 5.359139 , c 0.767379 , radioactivity, alpha decay, spontaneous fission, β- 1 2 3 decay and β+ decay) for isotopes of uranium is as c 4,28222 and =0 for even-even nuclei and =2 4 shown in Fig. 1. To identify the dominant decay for odd-A nuclei. mode, we have studied the competition between - different decay modes. Figure 2 shows the variation 2.4 β decay formula of logarithmic half-lives of cluster radioactivity, alpha β- decay process occurs in proton rich nuclei. decay, beta decay and spontaneous fission for Zhang et al.35 constructed a semi-empirical formula - different isotopes of uranium. for β decay half-lives and it is expressed as: The branching ratios are studied using the corresponding decay constants of binary fission, log T c Z c N c Z c shell(Z, N) 10 1 2 1 2 3 4 … (11) where shell correction term is expressed as: N 292 15 N 502 37 e e shell( Z ,N ) c5 N 852 9 N 1312 3 e e Z51.52 N80.52 1.9 c6e … (12) Z and N are the proton and neutron number of the parent nuclei, respectively.
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