Isomer ratios in fission fragments at high excitation

Cuninghame, J.G.; Goodall, J.A.B.; Freeman, J. E.; Newton, G.W.A.; Robinson, V.J.; Durrell, J. L.; Foote, G.S.; Grant, I. S.; Rathle, M

doi:10.1088/0305-4616/6/1/018

Cited by 20 publications

(21 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[31] for the α-induced fission of 238 U, in Ref. [15] where the isomer ratios of fission fragments at high excitation energies were studied, and in Ref. [43] where the dependence of fragment angular momentum on the entrance channel in 236 U fission was investigated.…”

Section: Discussion On the Isomeric Yield Ratiosmentioning

confidence: 99%

“…Extra unpaired nucleons exist even at the saddle point, where the nucleus is highly excited. Moreover, excitations corresponding to collective modes in which the two nascent fragments move relative to one another have, as a result, a part of the initial angular momentum to be retained by the fragments [15].…”

Section: Introductionmentioning

confidence: 99%

“…The results have been used to investigate collective rotational degrees of freedom [15,[40][41][42][43][44]. However, there are several challenges in these techniques, such as insufficient mass resolving power (MRP) in the separator, difficulties to study refractory elements, and inadequate knowledge of decay schemes.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

First isomeric yield ratio measurements by direct ion counting and implications for the angular momentum of the primary fission fragments

et al. 2018

View full text Add to dashboard Cite

Publisher's PDF Rakopoulos, V.; Lantz, M.; Solders, A.; Al-Adili, A.; Mattera, A.; Canete, Laetitia; Eronen, Tommi; Gorelov, Dmitry; Jokinen, Ari; Kankainen, Anu; Kolhinen, Veli; Moore, Iain; Nesterenko, Dmitrii; Penttilä, Heikki; Pohjalainen, Ilkka; Rinta-Antila, Sami; Simutkin, V.; Vilén, Markus; Voss, Annika; Pomp, S.Rakopoulos, V., Lantz, M., Solders, A., Al-Adili, A., Mattera, A., Canete, L., . . . Pomp, S. (2018). First isomeric yield ratio measurements by direct ion counting and implications for the angular momentum of the primary fission fragments. Physical Review C, 98 (2) We report the first experimental determination of independent isomeric yield ratios using direct ion counting with a Penning trap, which offered such a high resolution in mass that isomeric states could be separated. The measurements were performed at the Ion Guide Isotope Separator On-Line (IGISOL) facility at the University of Jyväskylä. The isomer production ratios of 81 Moreover, based on the isomeric yield ratios, the root-mean-square angular momenta (J rms ) of the fission fragments after scission were estimated using the TALYS code. The experimentally determined isomeric yield ratios, and consequently the deduced J rms , for 130 Sn are significantly lower compared to 128 Sn for both fissioning systems. This can be attributed to the more spherical shape of the fragments that contribute to the formation of 130 Sn, due to their proximity to the N = 82 shell closure. The values of J rms for 129 Sb are higher than 128 Sn for both reactions, despite the same neutron number of both nuclides (N = 78), indicating the odd-Z effect where fission fragments with odd-Z number tend to bear larger angular momentum than even-Z fragments. The isomer production ratio for the isotopes of Sn is more enhanced in the nat U(p, f ) reaction than in 232 Th(p, f ). The opposite is observed for 96 Y and 97 Y. These discrepancies might be associated to different scission shapes of the fragments for the two fission reactions, indicating the impact that the different fission modes can have on the isomeric yield ratios.

show abstract

Section: Discussion On the Isomeric Yield Ratiosmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

First isomeric yield ratio measurements by direct ion counting and implications for the angular momentum of the primary fission fragments

et al. 2018

View full text Add to dashboard Cite

show abstract

“…It was however shown by Cunninghame et al [5] that for such statistical excitation under thermal equilibrium since the fissioning nucleus also has a spin-distribution that might contribute spuriously to the fragment angular momentum of statistical origin, such spurious contribution need to be corrected to conserve the total angular momentum. However, for the individual pair of fragments the angular momenta arising from these random modes cancel out pairwise (due to their opposite directions) without violating the conservation principle.…”

Section: S I 2] T = L~ I/i N 9 K~ (7)mentioning

confidence: 99%

“…These observables include fragment angular momentum [1,2], prompt gammaray multiplicity [-21 and corresponding angular distribution [3] and angular distribution of the fragments [4]. In fission while the bending mode results in fragment angular momentum at low energy [2], tilting mode and statistical excitation of the rotational degrees were shown to be involved at high energy by Cunninghame et al [5]. The effect of equilibration of all the collective rotational modes including rigid rotation was shown by Moretto [6] for symmetric split into spherical fragments in heavy-ion reactions.…”

Section: Introductionmentioning

confidence: 99%

Influence of collective rotational degrees of freedom in medium energy fission

Datta

Dange

Sahakundu

et al. 1988

Z. Physik A - Atomic Nuclei

View full text Add to dashboard Cite

In the present work rms angular momenta have been deduced for the fission fragments corresponding to 131Tem'g and 133Tem'g in 232Th(~zr f) and 238U(e40MeV, f) systems from the radiochemically determined independent isomeric yield ratios and statistical model based analysis. For 131Te and 133Te the rms angular momenta deduced are 5.9-t-1.0 and 7.9___ 1.2 ta respectively in z3aTh(e4oMev, f) and 7.2+_0.6 and 8.0+0.8 ra respectively in z3SU(~ 4oraev,j~-c~ Comparison of the present data with the literature data for these fragments in the same compound nuclei 236U* and 24Zpu* at lower excitation energies shows increase in the fragment angular momentum with increasing excitation energy and angular momenta of the fissioning nuclei. Fragment angular momentum deduced theoretically for asymmetric and deformed fragments on the basis of thermal equilibration of the collective rotational degrees e.g., rigid rotation, wriggling, tilting, bending and twisting modes considering the effect of multichance fission, are in good agreement with the experimental observations.

show abstract

Fragment angular momenta in low and medium energy fission of242Pu

Tomar

Goswami

Das

et al. 1987

Z. Physik A - Atomic Nuclei

View full text Add to dashboard Cite

Independent isomeric yield ratios of 1288b were determined radiochemically in the thermal neutron induced fission of /4~pu and 34 MeV alpha particle induced fission of 2asu, both involving the same compound nucleus (242pu). Fragment angular momenta estimated from the measured isomer ratios using the statistical model analysis showed significantly larger fragment angular momenta in the medium energy fissioning system compared to the low energy fissioning system. This has been attributed to the effect of higher excitation energy and angular momentum in the entrance channel leading to increased fragment temperature, moments of inertia and angular velocity. An attempt was made to calculate the fragment angular momentum in the medium energy fission using the Fermi gas model for the fissioning nucleus, taking into account the multichance fission, saddle shapes of the fissioning nuclei and the angular velocity components of the fissioning nuclei both along and orthogonal to the fission axis. The calculated angular momenta agree well with the experimental results.Nuclear Reactions: 24aPu(nth,f); 238U(c~,f); 1/*Sb; isomeric yield ratios; Fragment angular momenta PACS: 25.85.Ge; 25.85.Ec

show abstract

Isomer ratios in fission fragments at high excitation

Cited by 20 publications

References 29 publications

First isomeric yield ratio measurements by direct ion counting and implications for the angular momentum of the primary fission fragments

First isomeric yield ratio measurements by direct ion counting and implications for the angular momentum of the primary fission fragments

Influence of collective rotational degrees of freedom in medium energy fission

Fragment angular momenta in low and medium energy fission of242Pu

Contact Info

Product

Resources

About