Function Of Fragment Mass Research Articles

Charge Distribution Studies in the Epi-Cadmium Neutron-Induced Fission of 241Pu

For the first time, charge distribution studies have been carried out in the epi-cadmium neutron-induced fission of 241Pu by measuring the fractional cumulative yields (FCYs) and independent yields of various fission products by using an off-line gamma-ray spectrometric technique. The average energy of the epi-cadmium neutron spectrum is 1.9 MeV. From the FCY values, the isobaric width parameter σZ, most probable charge ZP, and charge polarization ∆ΖEXPT as a function of fragment mass were obtained. On the other hand, from the independent yield values, isotopic width parameter σA; the most probable mass AP; and the elemental yields YZ of Sn, Sb, Te, I, Xe, Cs, Ba, La, Ce, and Pr were determined by using a nonlinear fit. From the YZ values, the proton even-odd effect δp was obtained for the first time. The present data were compared with similar data in the 241Pu(nth,f) reaction and epi-cadmium neutron-induced fission of 240Pu as well as other actinides to examine the role of the excitation energy and pairing effect.

Charge distribution studies in the epi-cadmium neutron induced fission of 233U

Charge distributions have been carried out in the epi-cadmium neutron induced fission of 233U for the first time by measuring the fractional cumulative yields (FCY) and independent yields (IY) of various fission products. The method of an off-line γ-ray spectrometric technique was used for the measurement. From the FCY values, the isobaric width parameter (σZ), most probable charge (ZP) and the charge polarization (ΔΖEXPT) as a function of fragment mass were obtained. Similarly, from the IY values, isotopic width parameter (σA), the most probable mass (AP) and the elemental yields (YZ) of Sn, Sb, Te, I, Xe, Cs, Ba, La, Ce and Pr were determined by using a non-linear fit. From the YZ values, the proton even-odd effect (δp) was obtained for the first time. The present data were compared with the similar data in the thermal neutron induced fission of 233U and other actinides to examine the role of excitation energy on charge distribution parameters.

Simulation of the 2E Technique on neutron multiplicity measurement as a function of fragment mass in spontaneous fission of 252Cf

A Monte Carlo simulation algorithm to investigate the measurement of the average prompt neutron multiplicity as a function of pre-neutron mass, ν(A), for fragments from the spontaneous fission of 252Cf is presented. The input data consist of experimental measurements of the kinetic energy and mass distributions obtained by Göök et al., and the values of ν(A) calculated using the FIFRELIN model by Piau et al., νth(A). We analyze the output curve, νsim(A), obtained by simulation of the 2E technique, which should ideally match νth(A). However, we find that νsim(A) exhibits a maximum value at A≈122, close to mass symmetry, while νth(A) has a maximum at A≈118. Additionally, we observe that νsim(A) > νth(A) for A< 90 and A> 169, respectively. We attribute this discrepancy to inaccuracies in the relationship between provisional mass and the pre-neutron mass used in the 2E technique for data processing in each fission event.

Charge distribution studies in the epi-cadmium neutron induced fission of 238Pu

Studies on charge distribution have been carried out in the epi-cadmium neutron induced fission of 238Pu for the first time. Experimentally fractional cumulative yields (FCY) and independent yields (IY) of various fission products have been measured by using an off-line γ-ray spectrometric technique. From the FCY values, the charge distribution parameters such as the isobaric width parameter (σZ), most probable charge (ZP) and the charge polarization (ΔΖEXPT) as a function of fragment mass were obtained. On the other hand, from the measured IY values, isotopic width parameter (σA), the most probable mass (AP) and the elemental yields (YZ) of Sn, Sb, Te, I, Xe, Cs, Ba, La, Ce and Pr were determined by using a non-linear fit. From the YZ values, the proton even-odd effect (δp) was obtained for the first time. The isobaric and isotopic charge distribution parameters in the 238Pu(nf, f) reaction were compared with the similar data in the thermal neutron induced fission of 238Pu and other actinides to examine the role of excitation energy.

Study of various ground state decay mechanisms of Actinide nuclei* *Financial support from the Department of Science and Technology (DST), New Delhi, India in the form of a research project grant (CRG/2021/001144) is gratefully acknowledged.

The special property of the actinide mass region is that nuclei belonging to this group are radioactive and undergo different ground state processes, such as alpha decay, cluster radioactivity (CR), heavy particle radioactivity (HPR), and spontaneous fission (SF). In this study, the probable radioactive decay modes of the heavy mass region (Z = 89−102) are studied within the framework of the preformed cluster model (PCM). In the PCM, the radioactive decay modes are explored in terms of the preformation probability () and penetration probability (P) at the turning point , where the penetration of fragments is initiated [R = R (touching state) + (neck length parameter)]. First, the alpha decay half-lives are calculated for light and heavy nuclei, and points are obtained by optimizing the neck length parameter. These points are further employed to fix the Q-value dependent turning point ((Q)). Then, using the ((Q)) relation, the decay half-lives are computed, and the calculated results are compared with the available theoretical and experimental data. The isotopical trend of and P is studied with respect to the mass number of the parent and daughter nucleus, respectively. The CR and HPR channels are also explored, and a comparison of calculated data is conducted with the available literature. Comparative analysis of the fragmentation potential and preformation probability is carried out for alpha decay and SF. The mass distribution of the nuclei is studied as a function of fragment mass (A ) by considering the spherical and hot-compact deformation of the decaying fragments. Finally, the most probable fission fragments are identified using the fragmentation structure, and the corresponding fission fragment total kinetic energy of the identified fragments is calculated and compared with available data, wherever applicable.

Charge distribution of light mass fission products in the thermal neutron induced fission of 233U, 235U and 239Pu

Fractional cumulative yields (FCY) of various light mass fission products in the 233U(nth, f), 235U(nth, f) and 239Pu(nth, f) reactions were measured by using an off-line γ-ray spectrometric technique. The values of most probable charge (ZP) were obtained by using the width of isobaric charge distribution (σZ) of nearby fissioning systems with proper apportion. From the ZP values, the experimental charge polarization (ΔΖEXPT) as a function of fragment mass were also deduced. The ΔΖEXPT values for the light mass chains from the present work and for the heavy mass chains from earlier work show an oscillating nature in the interval of five mass units due to even-odd staggering. A local effect around the shell region and a systematic decreasing trend with the approach of symmetric split was also observed. The ΔΖMPE values based on minimum potential energy surface were theoretically calculated, which shows no oscillation but only a systematic decreasing trend with the approach of symmetric split due to the assumption of liquid drop behaviour of the fissioning nucleus.

Charge distribution of heavy mass fission products in the thermal neutron induced fission of 233U, 235U and 239Pu

Isobaric charge distribution has been carried out in the thermal neutron induced fission of 233U, 235U and 239Pu by measuring the fractional cumulative yields (FCY) of various heavy mass fission products within the range of 127–149. An off-line γ-ray spectrometric technique was used for the measurement of fission product activities. The width of the isobaric charge distribution (σZ), most probable charge (ZP) and thus the experimental charge polarization (ΔΖEXPT) as a function of fragment mass were obtained. It was found that the σZ values around the mass number 127–129 and 132–136 are lower due to the presence of spherical 50p and 82n shells. The ΔΖEXPT values show an oscillating nature in the interval of five mass units due to even-odd effect. The ΔΖEXPT values also show a decreasing trend with the approach of symmetric split besides an oscillating nature. The most probable charge (ZMPE) and thus the ΔΖMPE values based on the minimum potential energy surface were theoretically calculated, which show a systematic decreasing trend with the approach of symmetric split due to the liquid drop behaviour of the fissioning nucleus.

Charge distribution of light mass fission products in the fast neutron induced fission of 237Np, 241Am and 243Am

In the fast neutron induced fission of 237Np, 241Am and 243Am, fractional cumulative yields (FCY) of various light mass fission products have been measured for the first time by using an off-line γ-ray spectrometric technique. The most probable charge (ZP) and the experimental charge polarization (ΔΖEXPT) as a function of fragment mass were obtained. The ΔΖEXPT values for the light mass chains from the present work and for the heavy mass chains from earlier work show a decreasing trend towards symmetric split with fluctuations for some of the mass chains due to the effect of shell closure proximity. The ΔΖMPE values based on minimum potential energy surface were theoretically calculated, which also shows a systematic decrease trend with the approach of symmetric split without any fluctuation due to the liquid drop behaviour of the fissioning nucleus.

Charge distribution of light mass fission products in the 232U(nth, f), 238Pu(nth, f) and 244Cm(SF) reactions

Fractional cumulative yields (FCY) of various light mass fission products in the 232U (nth, f), 238Pu(nth, f) and 244Cm(SF) reactions were measured by using an off-line γ-ray spectrometric technique. The values of most probable charge (ZP) were obtained by using the width of isobaric charge distribution (σZ) of nearby fissioning systems with proper apportion. From the ZP values, the experimental charge polarization (ΔΖEXPT) as a function of fragment mass were also deduced. The ΔΖEXPT values for the light mass chains from the present work and for the heavy mass chains from earlier work show an oscillating nature in the interval of five mass units, which is due to even-odd effect. A local effect around the shell region for some mass chains and a systematic decreasing trend with the approach of symmetric split was also observed. The ΔΖMPE values based on minimum potential energy surface were theoretically calculated, which also shows a systematic decreasing trend with the approach of symmetric split due to the liquid drop behaviour of the fissioning nucleus.

Systematic Approach to Calculate the Total Kinetic Energy Distribution of Actinides for the Photofission Phenomenon

The total kinetic energy as a function of fragment mass (TKE/A) was calculated for photofission of $${}^{232}$$ Th, $${}^{234}$$ U, $${}^{238}$$ U, $${}^{240}$$ Pu, and $${}^{242}$$ Pu using a systematic statistical scission point model. In the proposed systematic method, all the energies involved in fission need to be expressed as a function of mass and atomic numbers of fission fragments. Therefore, the shell correction energy of fission fragments was approximated in terms of fission fragment mass numbers based on Ruben’s idea. The deformability parameter ( $$\alpha$$ ) of fission fragments was also formulated as a function of mass and atomic numbers of fission fragments by fitting the calculations and experimental data according to Terrell’s formulas. The calculated results are in good agreement with the experimental data, except for fragments with magic numbers, which their shell correction energy and deformability parameters change rapidly.

Prompt fission neutron yields in thermal fission ofU235and spontaneous fission ofCf252

Background: The sharing of excitation energy between the fission fragments is one of the key issues in studying nuclear fission. One way to address this is by studying prompt-fission neutron multiplicities as a function of other fission observables such as the mass, $\overline{\ensuremath{\nu}}\left(A\right)$. These are vital benchmark data for both fission and nuclear deexcitation models, putting constrains on the fragment excitation energy and hence on the competing prompt neutron/$\ensuremath{\gamma}$-ray emission. Despite numerous detailed studies, recent measurements done at JRC-Geel with the SCINTIA array in the epithermal region show surprisingly strong discrepancies to earlier thermal fission data and the Wahl systematics.Purpose: The purpose was to perform measurements of the prompt-fission neutron multiplicity, as a function of fragment mass and total kinetic energy (TKE), in $^{235}\mathrm{U}\left({\text{n}}_{\text{th}},\text{f}\right)$ and $^{252}\mathrm{Cf}\left(\text{sf}\right)$, to verify and extend the SCINTIA results. Another goal was to validate the analysis methods, and prepare for planned investigations at excitation energies up to 5.5 MeV.Methods: The experiments were conducted at the former 7 MV Van de Graaff facility in JRC-Geel, using a Twin Frisch-Grid Ionization Chamber and two liquid scintillation detectors. A neutron beam with an average energy of 0.5 MeV was produced via the $^{7}\mathrm{Li}$(p,n) reaction. The neutrons were thermalized by a 12 cm thick block of paraffin. Digital data acquisition systems were utilized. Comprehensive simulations were performed to verify the methodology and to investigate the role of the mass and energy resolution on measured $\overline{\ensuremath{\nu}}\left(A\right)$ and $\overline{\ensuremath{\nu}}\left(\text{TKE}\right)$ values. The simulation results also revealed that the $\ensuremath{\partial}\overline{\ensuremath{\nu}}(A)/\ensuremath{\partial}A$ and $\ensuremath{\partial}\overline{\text{TKE}}/\ensuremath{\partial}\overline{\ensuremath{\nu}}$ are affected by the mass and energy resolution. However, the effect is small for the estimated resolutions of this work. Detailed Fluka simulations were performed to calculate the fraction of thermal neutron-induced fission, which was estimated to be about $98%$.Results: The experimental results on $\overline{\ensuremath{\nu}}\left(A\right)$ are in good agreement with earlier data for $^{252}\mathrm{Cf}\left(\text{sf}\right)$. For $^{235}\mathrm{U}\left({\text{n}}_{\text{th}},\text{f}\right)$, the $\overline{\ensuremath{\nu}}\left(A\right)$ data is very similar to the data obtained with SCINTIA, and therefore we verify these disclosed discrepancies to earlier thermal data and to the Wahl evaluation. The experimental results on $\overline{\ensuremath{\nu}}\left(\text{TKE}\right)$ are also in agreement with the data at epithermal energies. For $^{252}\mathrm{Cf}\left(\text{sf}\right)$ a slope value of $\ensuremath{\partial}\overline{\text{TKE}}/\ensuremath{\partial}\overline{\ensuremath{\nu}}=\left(\ensuremath{-}12.9\ifmmode\pm\else\textpm\fi{}0.2\right)\phantom{\rule{0.28em}{0ex}}\mathrm{MeV}/\mathrm{n}$ was obtained. For $^{235}\mathrm{U}\left({\text{n}}_{\text{th}},\text{f}\right)$ the value is $\left(\ensuremath{-}12.0\ifmmode\pm\else\textpm\fi{}0.1\right)\phantom{\rule{0.28em}{0ex}}\mathrm{MeV}/\mathrm{n}$. Finally, the neutron spectrum in the center-of-mass system was derived and plotted as a function of fragment mass.Conclusions: This work clearly proves the lack of accurate correlation between fission fragment and neutron data even in the best-studied reactions. The new results highlight the need of a new evaluation of the prompt-fission multiplicity for $^{235}\mathrm{U}\left({\text{n}}_{\text{th}},\text{f}\right)$.

Oversize of the average prompt neutron multiplicity measured by the 1V1E method in the symmetric region of thermal neutron-induced fission of 239Pu

Using a Monte Carlo method, the measurement by the 1V1E technique of the average prompt neutron multiplicity as a function of the mass of fragments from the thermal neutron-induced fission of 239Pu is simulated. The input data, associated with the masses of complementary primary fragments (A1, A2), consist of the yield (Y), the average total kinetic energy (TKE-) and its standard deviation (σTKE), the average prompt neutron multiplicity (ν-s, a sawtooth approach of an experimental curve ν-), and the slope of neutron multiplicity against total kinetic energy, -dν/d<TKE>, plotted as a function of fragment mass. The output data, associated with the provisional masses of complementary fragments (m1∗, m2∗) calculated with the 1V1E method, consist of the simulated quantities Y, TKE-, σTKE, N-, comparable to the measured ones. In comparison with ν-s, N- and ν-are oversized in the region of light fragment masses near the symmetric fission. To interpret the results, the neighboring masses ratio RA =YA+1/Y(A) and the term FA=A-m∗, where m∗ is the average of provisional mass as a function of A, are defined. It is shown that N--ν-s and ν--ν-s are correlated with -F(R-1). It is concluded that the oversize of ν- relative to ν-s is due to the interplay of the prompt neutron emission and the slope of the mass yield curve.

Behavior of the average prompt neutron multiplicity as a function of post-neutron fragment mass in correlation with the pre-neutron fragment mass distribution in thermal neutron induced fission of 235U and 233U

Abstract A Monte Carlo simulation is performed in order to correlate the average prompt neutron multiplicity as a function of post- and pre-neutron fragment mass ( n - ( m ) and ν - ( A ) , respectively). This is applied for 235,233U(nth,f). The input of the simulation consists of quantities related to pre-neutron fragments, i.e. the mass yield Y ( A ) , the average kinetic energy E - ( A ) , its standard deviation σ E ( A ) and a function ν - s ( A ) (composed by three jointed segments) which approximates the sawtooth shape of the experimental prompt neutron multiplicity ν - ( A ) . The ratio of neighboring mass yields R A = Y ( A + 1 ) / Y ( A ) is introduced. It is found that n - ν - s ( n - > ν - s ) approximately in the same ranges of A where R 1 ( R > 1 ) . The average prompt neutron multiplicity as a function of fragment mass N - μ measured by using the 2 E method is also simulated. Its behaviour is similar to the one mentioned above.

Comprehensive overview of the Point-by-Point model of prompt emission in fission

The investigation of prompt emission in fission is very important in understanding the fission process and to improve the quality of evaluated nuclear data required for new applications. In the last decade remarkable efforts were done for both the development of prompt emission models and the experimental investigation of the properties of fission fragments and the prompt neutrons and $\gamma$ -ray emission. The accurate experimental data concerning the prompt neutron multiplicity as a function of fragment mass and total kinetic energy for 252Cf(SF) and 235 (n, f) recently measured at JRC-Geel (as well as other various prompt emission data) allow a consistent and very detailed validation of the Point-by-Point (PbP) deterministic model of prompt emission. The PbP model results describe very well a large variety of experimental data starting from the multi-parametric matrices of prompt neutron multiplicity $\nu (A,TKE)$ and $\gamma$ -ray energy $E_{\gamma}(A,TKE)$ which validate the model itself, passing through different average prompt emission quantities as a function of A (e.g., $\nu(A)$ , $E_{\gamma}(A)$ , $\langle \varepsilon \rangle (A)$ etc.), as a function of TKE (e.g., $\nu (TKE)$ , $E_{\gamma}(TKE)$ ) up to the prompt neutron distribution $P (\nu)$ and the total average prompt neutron spectrum. The PbP model does not use free or adjustable parameters. To calculate the multi-parametric matrices it needs only data included in the reference input parameter library RIPL of IAEA. To provide average prompt emission quantities as a function of A, of TKE and total average quantities the multi-parametric matrices are averaged over reliable experimental fragment distributions. The PbP results are also in agreement with the results of the Monte Carlo prompt emission codes FIFRELIN, CGMF and FREYA. The good description of a large variety of experimental data proves the capability of the PbP model to be used in nuclear data evaluations and its reliability to predict prompt emission data for fissioning nuclei and incident energies for which the experimental information is completely missing. The PbP treatment can also provide input parameters of the improved Los Alamos model with non-equal residual temperature distributions recently reported by Madland and Kahler, especially for fissioning nuclei without any experimental information concerning the prompt emission.

Charge distribution of light mass fission products in the fast neutron induced fission of 232Th, 238U, 240Pu and 244Cm

Fractional cumulative yields (FCY) of various light mass fission products in the fast neutron induced fission of 232Th, 238U, 240Pu and 244Cm have been determined by using the off-line γ-ray spectrometric technique. From present and literature data, width of isobaric charge distribution (σZ), the most probable charge (ZP) and the experimental charge polarization (∆ΖEXPT) as a function of fragment mass were deduced. The ∆ΖEXPT values from the present work for light mass chains and earlier work for heavy mass chains show oscillating nature due to nuclear structure effect. The ∆ΖMPE values based on minimum potential energy surface were theoretically calculated, which shows a systematic decrease trend with the approach of symmetric split due to the liquid drop behaviour of the fissioning nucleus.

The new double energy-velocity spectrometer VERDI

VERDI (VElocity foR Direct particle Identification) is a fission-fragment spectrometer recently put into operation at JRC-Geel. It allows measuring the kinetic energy and velocity of both fission fragments simultaneously. The velocity provides information about the pre-neutron mass of each fission fragment when isotropic prompt-neutron emission from the fragments is assumed. The kinetic energy, in combination with the velocity, provides the post-neutron mass. From the difference between pre- and post-neutron masses, the number of neutrons emitted by each fragment can be determined. Multiplicity as a function of fragment mass and total kinetic energy is one important ingredient, essential for understanding the sharing of excitation energy between fission fragments at scission, and may be used to benchmark nuclear de-excitation models. The VERDI spectrometer design is a compromise between geometrical efficiency and mass resolution. The spectrometer consists of an electron detector located close to the target and two arrays of silicon detectors, each located 50 cm away from the target. In the present configuration pre-neutron and post-neutron mass distributions are in good agreement with reference data were obtained. Our latest measurements performed with spontaneously fissioning 252Cf is presented along with the developed calibration procedure to obtain pulse height defect and plasma delay time corrections.

Analysis of prompt fission neutrons in235U(nth,f) and fission fragment distributions for the thermal neutron induced fission of234U

This paper presents the ongoing analysis of two fission experiments. Both projects are part of the collaboration between the nuclear reactions group at Uppsala and the JRC-IRMM. The first experiment deals with the prompt fission neutron multiplicity in the thermal neutron induced fission of 235 U(n,f). The second, on the fission fragment properties in the thermal fission of 234 U(n,f).The prompt fission neutron multiplicity has been measured at the JRC-IRMM using two liquid scintillators in coincidence with an ionization chamber. The first experimental campaign focused on 235 U(n th ,f) whereas a second experimental campaign is foreseen later for the same reaction at 5.5 MeV. The goal is to investigate how the so-called sawtooth shape changes as a function of fragment mass and excitation energy. Some harsh experimental conditions were experienced due to the large radiation background. The solution to this will be discussed along with preliminary results.In addition, the analysis of thermal neutron induced fission of 234 U(n,f) will be discussed. Currently analysis of data is ongoing, originally taken at the ILL reactor. The experiment is of particular interest since no measurement exist of the mass and energy distributions for this system at thermal energies. One main problem encountered during analysis was the huge background of 235 U(n th ,f). Despite the negligible isotopic traces in the sample, the cross section difference is enormous. Solution to this parasitic background will be highlighted.

Sensitivity of Prompt Neutron Multiplicity to Fission Fragment Characteristics

The Point-by-Point (PbP) model as well as the related computer code is a useful tool to provide different prompt emission data [as a function of fragment mass A, fragment charge Z, total kinetic energy (TKE), and total average ones]. The present work focuses on the sensitivity of prompt neutron multiplicity to different properties of the fission fragments. In the construction of the fragmentation range of the PbP treatment, the use of different Z prescriptions affects the multiparametric matrices of different fragment and prompt emission quantities q(A,Z,TKE). The nonnegligible influence of how the most probable charge is considered (as unchanged charge distribution without or with the charge deviations ΔZ as a function of A or an average ΔZ value), as well as the number of Z taken at each A, is discussed. The calculated average prompt emission quantities as a function of A, as a function of TKE, and total average ones depend on the accuracy of experimental Y(A,TKE) distributions. The prompt neutron multiplicity of complementary fragments vpair (A) has a weak dependence on the total excitation energy (TXE) partition between complementary fully accelerated fragments. This assures a good prediction of the average prompt neutron multiplicity as a function of TKE and of the total average one even in the case of a rough or inappropriate TXE partition. The systematic behavior revealed by the experimental ratio vH/vpair as a function of AH together with the weak dependence of vpair(A) on the TXE partition can be exploited—in the absence of experimental v(A) information—for an indirect verification of predicted v(A).

Correlation between the Prompt Neutron Multiplicity and Prompt Gamma-ray Energy in the Frame of the Point-by-Point Model

The Point-by-Point (PbP) model was used to calculate average prompt γ-ray energy and multiplicity as a function of fragment mass and total kinetic energy, Eγ(A,TKE), Eγ(A), Nγ(A), <Eγ>(TKE) for 252Cf(SF), 233,235U(nth,f) and 239Pu(nth,f). The results describe very well the experimental data including the linear correlation between the prompt γ-ray energy and prompt neutron multiplicity. Contrary to the experimentally observed increase of prompt neutron multiplicity ν(A) with incident neutron energy for heavy fragments only for 235U and 239Pu and confirmed by the PbP results for 234,235U, 237Np and 232Th, Eγ(A) does not exhibit a similar behaviour. Total <Eγ>, <Nγ>, <ɛγ> are obtained in overall good agreement with the experimental data measured in the 1970s – 1980s. The linear correlation <Eγ>=p<νp>+q revealed by the experimental data of Nifenecker, Pleasonton and Fréahut is well reproduced by the global parameterization of Vladuca and Tudora, 2001. This parameterization was deduced by fitting the results of the (n,n’) and (n,γ) competition obtained from nuclear reaction calculations (treated by spherical optical and Hauser-Feshbach statistical models) applied at that time on a limited number of nuclei appearing as fission fragments (in the frame of the 7 points approximation). The experimental Eγ>, <Nγ> and < ɛγ> data recently measured for 252Cf(SF) and 235U(nth,f) can be reproduced by keeping the slope provided by the global parameterization and an adjustment with about 7% for the intercept. This points to needed refinement of the global parameterization by e.g. new nuclear reaction calculations for light fission fragments isotopes.

Prompt fission neutron emission calculations and description of sub-barrier fission cross section resonances for 234U()

Abstract Prompt emission quantities of 234U( n , f ) (average quantities as a function of fragment mass, average quantities as a function of total kinetic energy (TKE) and total average quantities) have been calculated within the Point-by-Point model. The recently measured fission fragment distributions at incident energies (En) ranging from 0.2 MeV to 5 MeV have been used. The insensibility of the fragment pair multiplicity ν pair to the partition of total excitation energy (TXE) between complementary fully accelerated fission fragments has been confirmed. This gives confidence in the predicted total average prompt emission data as a function of En and of average quantities as a function of TKE at different incident energies of 234U( n , f ). The systematic behavior of experimental ratios ν H / ν pair as a function of heavy fragment mass number A H together with the TXE partition based on modeling at scission allow the parameterization of the excitation energy ratio E H ⁎ / TXE . This opens up the possibility to provide ν ( A ) of 234U in the absence of any experimental data. For the first time the calculation of 〈 ν 〉 ( TKE ) at many En revealed two interesting aspects: the slope d TKE / d ν does not vary with En and the flattening of 〈 ν 〉 at low TKE values is more pronounced at low incident energies. The correlation between the sub-barrier resonant behavior of the fission cross section of fertile actinides (characterizing the pre-scission stage) and the visible fluctuations of their fission fragment and prompt neutron emission data (characterizing the post-scission stage), already discussed in the case of 238U( n , f ) is outlined and quantitatively supported by 234U( n , f ), too. The pronounced vibrational resonances in the experimental fission cross section of 234U placed below 1 MeV can be described by the statistical model for reaction cross section calculation including the optical model for fission.