Independent Isomeric Yield Ratios Research Articles

Independent isomeric yield ratios of fission products in the epi-cadmium neutron induced fission of 235U

In the epi-cadmium neutron induced fission of 235U, independent isomeric yield ratios (IR) of fission products 130,132Sb, 131,133Te, 134,136I, 135Xe and 138Cs have been measured by using an off-line gamma-ray spectrometric technique. The average neutron energy of the epi-cadmium reactor neutron spectrum is 1.9 MeV. From the IR values, the root mean square fragment angular momenta (JRMS) were deduced by using spin dependent statistical model analysis. The IR and JRMS values of considered fission products in the epi-cadmium neutron induced fission of 235U were compared with the literature data in the thermal neutron induced fission of 235U to examine the influence of excitation energy on nuclear structure effect.

Independent isomeric yield ratios of fission products in the epi-cadmium neutron-induced fission of 245Cm

Abstract Independent isomeric yield ratios (IR) of 128,130,132Sb, 131,133Te, 132,134I, 135Xe and 138Cs in the epi-cadmium neutron-induced fission of 245Cm have been measured for the first time by using an off-line gamma-ray spectrometric technique. The average energy of the epi-cadmium neutron spectrum (<E n >) is 1.9 MeV. From the IR values, root mean square fragment angular momenta (J RMS) were deduced by using the spin dependent statistical model analysis. The IR and JRMS values of the fission products from the present work were compared with the literature data in the thermal neutron-induced fission of 245Cm to examine the role of excitation energy. Effect of nuclear structure on J RMS value was also examined.

Independent isomeric yield ratios of fission products in the epi-cadmium neutron induced fission of 239Pu

Measurement of independent isomeric yield ratios (IR) of 128,130,132Sb, 131,133Te, 132.134,136I, 135Xe and 138Cs have been carried out for the first time in the epi-cadmium neutron induced fission of 239Pu by using an off-line gamma-ray spectrometric technique. The average neutron energy (<En>) of the epi-cadmium reactor neutron spectrum is 1.9 MeV. From the IR values, root mean square fragment angular momenta (JRMS) were deduced by using spin dependent statistical model analysis. Effect of nuclear structure on JRMS values was examined. The present data in the epi-cadmium neutron induced fission of 239Pu were compared with the similar data in the thermal neutron induced fission of 239Pu to examine the role of excitation energy on JRMS values.

Independent isomeric yield ratios of fission products in the epi-cadmium neutron induced fission of 233U

The independent isomeric yield ratios (IR) of 128,130,132Sb, 131,133Te, 132,134,136I, 135Xe and 138Cs have been measured in the epi-cadmium neutron induced fission of 233U by using an off-line gamma-ray spectrometric technique. The average neutron energy of the epi-cadmium reactor neutron spectrum is 1.9 MeV. The root mean square fragment angular momenta (JRMS) were deduced from the IR values by using spin dependent statistical model analysis. The IR and JRMS values of considered fission products in the epi-cadmium neutron induced fission of 233U were compared with the literature data in the thermal neutron induced fission of 233U to examine the influence of excitation energy on nuclear structure effect.

Independent isomeric yield ratios of fission products in the epi-cadmium neutron induced fission of 238Pu

In the epi-cadmium neutron induced fission of 238Pu, independent isomeric yield ratios (IR) of 128,130,132Sb, 131,133Te, 134,136I, 135Xe and 138Cs have been measured by using an off-line γ-ray spectrometric technique. The average neutron energy of the epi-cadmium reactor neutron spectrum is 1.9 MeV. From the IR values, root mean square fragment angular momenta (JRMS) were deduced by using spin dependent statistical model analysis. The JRMS values from the present work in the epi-cadmium neutron induced fission of 238Pu were compared with the literature data in the thermal neutron induced fission of 238Pu to examine the role of excitation energy. Effect of nuclear structure on JRMS values was examined.

Independent isomeric yield ratios of fission products in the epi-cadmium neutron induced fission of 241Pu

Abstract Independent isomeric yield ratios (IR) of 130,132Sb, 131,133Te, 134,136I, 135Xe and 138Cs have been measured in the epi-cadmium neutron induced fission of 241Pu by using an off-line gamma-ray spectrometric technique. The average neutron energy (&lt;E n&gt;) of the epi-cadmium reactor neutron spectrum is 1.9 MeV. From the IR values, root mean square fragment angular momenta (J RMS) were deduced by using spin dependent statistical model analysis. Effect of nuclear structure on J RMS values was examined. The present data in the epi-cadmium neutron induced fission of 241Pu were compared with the similar data in the thermal neutron induced fission of 241Pu to examine the role of excitation energy on fragment angular momentum.

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

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 ...

Measurements of isomeric yield ratios of fission products from proton-induced fission onnatU and232Th via direct ion counting

Independent isomeric yield ratios (IYR) of 81Ge, 96Y, 97Y, 97Nb, 128Sn and 130Sn have been determined in the 25 MeV proton-induced fission of natU and 232Th. The measurements were performed at the ...

Measurement of isomeric ratios for 89g,mZr, 91g,mMo, and 97g,mNb in the bremsstrahlung end-point energies of 16 and 45-70 MeV

The independent isomeric yield ratios of 89g,mZr from the natZr(\( \gamma\),xn) reactions and those of 91g, mMo and 97g,mNb from the natMo(\( \gamma\),x) reactions with the bremsstrahlung end-point energy of 45-70 MeV were determined by an off-line \(\gamma\)-ray spectrometric technique using the 100 MeV electron linac at the Pohang Accelerator Laboratory, Korea. The isomeric yield ratios of 89g,mZr and 97g,mNb from the natZr(\( \gamma\), xn) and natMo(\( \gamma\),x) reactions at the bremsstrahlung end-point energy of 16MeV were also determined by the same technique using the 20MeV electron linac at Helmholtz-Zentrum Dresden-Rossendorf, Germany. The measured isomeric yield ratios of 89g,mZr, 91g,mMo, and 97g,mNb were compared with literature data to examine the role of the Giant Dipole Resonance (GDR). The isomeric yield ratios of the 89g,mZr, 91g,mMo, and 97g,mNb from the above reactions were also calculated by using the computer code TALYS 1.6 and compared with the experimental data to examine the validity of the theoretical model for independent isomeric yield ratio calculations.

Isomeric yield ratios of 148Pm from the natSm(γ, x) and the natNd(p, xn) reactions

The independent isomeric yield ratios of 148Pm from the natSm(γ, x) reaction at the end-point bremsstrahlung energy of 45–64 MeV have been determined using an off-line γ-ray spectrometric technique at the 100 MeV electron linac of Pohang accelerator laboratory, Pohang, Korea. We also have determined the isomeric yield ratios of 148Pm from the natNd(p,xn) reactions in the proton energy of 5.08–44.72 MeV by a stacked-foil activation and an off-line γ-ray spectrometric techniques at the MC-50 cyclotron of the Korean Institute of Radiological and Medical Sciences, Korea. The determined isomeric yield ratios of 148Pm were compared with literature data and theoretical values estimated by the TALYS 1.4. The present data along with the similar data from literature at other energies shows that the isomeric yield ratio of 148Pm increases with the excitation energy both in the natSm(γ, x) and the natNd(p, xn) reactions. The isomeric yield ratios of 148Pm from the natNd(p, xn) reactions are always higher than those from the natSm(γ, x) reactions at the same excitation energy, which indicate the role of input angular momentum besides excitation energy.

Isomeric yield ratios of 87m,gY from different nuclear reactions

The independent isomeric yield ratios of 87m,gY produced from the 93Nb(γ, α2n) and natZr(γ, pxn) reactions with the end-point bremsstrahlung energy of 45–70 MeV have been determined by an off-line γ-ray spectrometric technique using 100 MeV electron linac at the Pohang accelerator laboratory, Korea. The isomeric yield ratios of 87m,gY were also determined from the natZr(p, αxn) and the 89Y(p,p2n) reactions with EP = 15–45 MeV as well as those from the 89Y(α, α2n) reaction with Eα = 32–43 MeV using the MC-50 cyclotron at the Korea Institute of Radiological and Medical Science, Korea. The isomeric yield ratios of 87m,gY from the present work in the 93Nb(γ, α2n), natZr(γ, pxn), natZr(p, αxn), 89Y(p,p2n), and 89Y(α, α2n) reactions were compared with those of the literature data in the 85Rb(α, 2n), the 86,87,88Sr(d, xn), 89Y(n,3n), and the 89Y(γ, 2n) reactions to examine the role of target, projectiles, and ejectiles through compound nucleus excitation energy and input angular momentum. The isomeric yield ratios of 87m,gY in the above eleven reactions were also calculated using the computer code TALYS 1.4 and compared with the experimental data. The different behaviors between photon- and neutron-induced reactions and charged-particle-induced reactions are discussed from the viewpoint of compound and non-compound (pre-equilibrium) process.

Independent isomeric yield ratios of 95m,gNb in the natMo(γ, pxn) and natZr(p, xn) reactions

The independent isomeric yield ratios of 95m,gNb from the natMo(γ, pxn) reactions with bremsstrahlung end-point energies of 45, 50, 55, 60, and 70 MeV were determined by an activation and an off-line γ-ray spectrometric technique at the Pohang accelerator laboratory (PAL), Korea. The isomeric yield ratios of 95m,gNb from the natZr(p, xn) reactions were also determined in eight different proton energies within 19.4–44.7 MeV by a stacked-foil activation and an off-line γ-ray spectrometric technique using the MC-50 cyclotron of Korea Institute of Radiological and Medical Sciences (KIRAMS), Korea. The measured isomeric yield ratios of 95m,gNb from the present work and the literature data in the natMo(γ, pxn) and natZr(p, xn) reactions were compared with the similar literature data in the natMo(p, αxn) reactions. It was found that the isomeric yield ratio of 95m,gNb increases with projectile energy, which indicate the effect of excitation energy. However, at the same excitation energy, the isomeric yield ratios of 95m,gNb in the natZr(p, xn) and natMo(p, αxn) reactions are higher than those in the natMo(γ, pxn) reaction, which indicates the role of input angular momentum. The isomeric yield ratios of 95m,gNb in the natMo(γ, pxn), natZr(p, xn), and natMo(p, αxn) reactions were also calculated using computer code TALYS 1.4. The calculated isomeric yield ratios of 95m,gNb from three reactions increase with excitation energy. However, in all the three reactions, the calculated values are significantly higher than the experimental data.

Isomeric yield ratios for the natNd(γ, xn) 139m,g; 141m,gNd reactions in the bremsstrahlung energy region from 45 to 60 MeV

The independent isomeric yield ratios (IR) for the 139m,gNd and the 141m,gNd isomeric pairs produced from the natNd(γ, xn) reactions were determined by the activation and the off-line γ-ray spectrometric technique at the end-point bremsstrahlung energies of 45, 50, 55, and 60 MeV in the 100 MeV electron Linac of the Pohang accelerator laboratory, Korea. The present IR for the 141m,gNd isomeric pair were compared with those from the literature measured by the bremsstrahlung and the neutron to examine the role of excitation energy. The obtained IR for the 139m,gNd and the 141m,gNd isomeric pairs from natNd(γ, xn) reactions were compared with those from the 141Pr(p, x), the natCe(3He, x), and the 136Ce(α, n) reactions to examine the role of parameters in entrance channel i.e. excitation energy and the effect of the input angular momentum. The present IR of 139m,gNd and 141m,gNd were compared with those calculated by using the TALYS 1.4 code as well as those from the literature data of above mentioned reactions.

Single-particle spin effect on fission fragment angular momentum

Independent isomeric yield ratios (IYR) of 128Sb, 130Sb, 132Sb, 131Te, 133Te, 132I, 134I, 136I, 135Xe, and 138Cs have been determined in the fast neutron-induced fission of 243Am using the radiochemical and γ-ray spectrometric technique. From the IYR, fragment angular momenta (J rms) have been deduced using the spin-dependent statistical model analysis. From the J rms-values and experimental kinetic energy data deformation parameters (β) have been deduced using the pre-scission bending mode oscillation model and the statistical model. The J rms- and β-values of fission fragments from the present and earlier work in the odd-Z fissioning systems ( 238Np * , 242Am * and 244Am * ) are compared with the literature data in the even-Z fissioning systems ( 230, 233Th * , 233, 234, 236, 239U * , 239, 240, 241, 242Pu * , 244Cm(SF), 245, 246Cm * , 250Cf * and 252Cf(SF)) to examine the role of single-particle (proton) spin effect. It was observed that i) in all the fissioning systems J rms- and β-values of the fragments with spherical 82n shell and even-Z products are lower than the fragments away from the spherical neutron shell and odd-Z products, which indicate the effect of nuclear structure. ii) For both even-Z and odd-Z fission products J rms-values increase with Z F 2/A F due to increase in Coulomb torque. iii) The J rms- and β-values of even-Z fission products are comparable in all the fissioning systems. However, for odd-Z fission products they are slightly higher in the odd-Z fissioning systems compared to their adjacent even-Z fissioning systems. This is possible due to the contribution of the extra single-particle (proton) spin of the odd-Z fissioning systems to their odd-Z fragments. iv) The yield-weighted fragment angular momentum and elemental yields profile shows an anti-correlation in even-Z fissioning systems but not in the odd-Z fissioning systems.

Angular momentum of fission fragments in low energy fission of actinides

Independent isomeric yield ratios (IYR) of $^{128}\mathrm{Sb}$, $^{130}\mathrm{Sb}$, $^{132}\mathrm{Sb}$, $^{131}\mathrm{Te}$, $^{133}\mathrm{Te}$, $^{132}\mathrm{I}$, $^{134}\mathrm{I}$, $^{136}\mathrm{I}$, $^{135}\mathrm{Xe}$, and $^{138}\mathrm{Cs}$ have been determined in fast neutron induced fission of $^{232}\mathrm{Th}$, $^{238}\mathrm{U}$, $^{240}\mathrm{Pu}$, and $^{244}\mathrm{Cm}$ as well as in thermal neutron induced fission of $^{232}\mathrm{U}$ and $^{238}\mathrm{Pu}$ using radiochemical and offline $\ensuremath{\gamma}$-ray spectrometric techniques. From the IYR, fragment angular momenta (${J}_{\mathrm{rms}}$) have been deduced using a spin-dependent statistical model analysis. These data along with the literature data for ${^{230}\mathrm{Th}}^{\ensuremath{\ast}}$, ${^{234}\mathrm{U}}^{\ensuremath{\ast}}$, ${^{236}\mathrm{U}}^{\ensuremath{\ast}}$, ${^{240}\mathrm{Pu}}^{\ensuremath{\ast}}$, ${^{242}\mathrm{Pu}}^{\ensuremath{\ast}}$, $^{244}\mathrm{Cm}$(SF), ${^{246}\mathrm{Cm}}^{\ensuremath{\ast}}$, ${^{250}\mathrm{Cf}}^{\ensuremath{\ast}}$, and $^{252}\mathrm{Cf}$(SF) for fifteen even-$Z$ fissioning systems show the following important features: (i) The ${J}_{\mathrm{rms}}$ of the odd-$Z$ fission products are higher than those of the even-$Z$ fission products, indicating the odd-even effect. For both the odd-$Z$ and even-$Z$ fission products, the ${J}_{\mathrm{rms}}$ increase with ${Z}_{F}^{2}/{A}_{F}$. (ii) The ${J}_{\mathrm{rms}}$ of fragments with spherical 50-$p$ and 82-$n$ shells are lower compared to those of fragments outside the spherical shell, indicating the effect of shell closure proximity. (iii) The ${J}_{\mathrm{rms}}$ of the fission products increase with mass number in spite of fluctuations in shell closure proximity and odd-even effects but do not show any correlation with the neutron emission curve. (iv) In all fifteen even-$Z$ fissioning systems from Th to Cf, the yield-weighted ${J}_{\mathrm{rms}}$ values show an anticorrelation with the elemental yields. (v) The odd-even fluctuation on ${J}_{\mathrm{rms}}$ does not change drastically from Th to Cf, unlike the proton odd-even effect (${\ensuremath{\delta}}_{p}$) which decreases significantly with the increase of Coulomb parameter (${Z}_{F}^{2}/{A}_{F}^{1/3}$).

Fission fragment angular momentum in ODD-Z fissioning systems

Independent isomeric yield ratios of 128Sb, 130Sb, 132, 131Te, 133Te, 132I, 134I, 136I, 135Xe and 138Cs have been determined in the fast neutron induced fission of 237Np and 241Am using radiochemical and gamma spectrometric technique. From the independent isomeric yield ratios, fragment angular momenta (Jrms) have been deduced using spin-dependent statistical model analysis. Comparison of these data with the literature data for even-Z fissioning systems shows the following important features: (i) Angular momenta for fragments with spherical 82n shell and even-Z products are lower compared to the fragments with out the 82n shell and odd-Z products indicating the effect of nuclear structure. (ii) Angular momentum of even-Z products in all the fissioning systems are comparable where as for odd-Z products it is slightly higher in the odd-Z fissioning systems than in the adjacent even-Z fissioning systems. This indicates the role of single particle on fragment angular momentum in odd-Z fissioning systems.

Some important aspects of fragment angular momentum in medium energy fission of 238U

Independent isomeric yield ratios of 131Te, 133T and 134I hava been determined at five different energies in the range of 25–44 MeV alpha particle induced fission of 238U using radiochemical and gamma spectrometric techniques. From the independent isomeric yield ratios, fragment angular momenta ( J rms) have been deduced using a statistical model analysis. The J rms were also calculated theoretically based on thermal equilibration of various collective modes after considering the occurrence of multichance fission. These data and the literature data for various fragments in the mass region 126–136 in 238U(α,f), 238U(p,f) and 238U(γ,f) show the following important features: (i) Both the entrance channel excitation energy and input angular momentum affect the fragment angular momentum in the exit channel. (ii) There are two groups of fission products from the point of view of change of fragment angular momentum with increase in excitation energy and input angular momentum. (iii) Fragment angular momentum depends on nuclear structure effect such as shell closure proximity and odd-even effect. (iv) The fragment angular momentum calculated theoretically based on statistical equilibration of various collective modes are in good agreement with the experimental values indicating the validity of such an assumption.

Systematics of fragment angular momentum in low-energy fission of actinides

Independent isomeric yield ratios for 128Sb, 130Sb, 132Sb, 131Te, 133Te, 132I, 134I, 136I, 135Xe and 138Cs in 229Th(nth, f), for 136I in 233U(nth, f) and 239Pu(nth, f), for 138Cs in 235U(nth, f), for 130Sb, 136I and 135Xe in 241Pu(nth, f), for 128Sb, 130Sb, 130Sb, 132Sb, 131Te, 133Te, 134I, 136I, 135Xe and 138Cs in 245Cm(nth, f) and for 128Sb, 130Sb, 132Sb, 136I and 135Xe in 252Cf(S.F.) have been determined using radiochemical and gamma-ray spectrometric techniques. From the isomeric yield ratios, fragment angular momenta (Jrms) have been deduced using spin-dependent statistical-model analysis. These data along with the literature data in the above fissioning systems as well as in 249Cf(nth, f) show several important features. These features are: (i) Angular momenta for fragments with spherical 50-proton shell, 82-neutron shell and even-Z products are lower compared to the fragments with deformed 88-neutron shell, no shells and odd-Z products indicating the nuclear-structure effects. (ii) Fission fragment Jrms has a nearly inverse correlation with elemental yield in fissioning systems from 230Th∗ to 252Cf possibly due to coupling between the collective and intrinsic degrees of freedom. (iii) Although the percentage odd-even effect in the elemental yield decreases from 230Th∗ to 250Cf∗ and 252Cf, the odd-even fluctuation on fragment Jrms remains nearly the same in spite of the inverse correlation. This possibly indicates the effect of fragment deformation. (iv) Fission-product elemental yield as well as angular momentum have no definite correlation with fissionability since both are decided near the scission point.

Emission-angle dependence of fission fragment spin.

The average spin of fission fragment at specific mass asymmetry has been obtained as a function of emission angles in the $^{238}\mathrm{U}$ (${\mathrm{\ensuremath{\alpha}}}_{39.1\mathrm{M}\mathrm{e}\mathrm{V}}$,f) system from radiochemically determined independent isomeric yield ratios of $^{132}\mathrm{I}$. The fragment average spin is seen to decrease from 11.2\ensuremath{\Elzxh} to 6.5\ensuremath{\Elzxh} with change in emission angle from 90\ifmmode^\circ\else\textdegree\fi{} to 20\ifmmode^\circ\else\textdegree\fi{}, due to the angle-dependent tilting component over and above the statistical wriggling, bending, and twisting components as per the collective mode model. Effects of entrance channel parameters and multichance fission are also discussed.

Effect of entrance channel parameters on fission fragment angular momentum in medium energy fission

Independent isomeric yield ratios of132I were radiochemically determined in alpha particle induced fission of238U in the energy range 25–44 MeV. Fission fragment angular momenta were deduced from the measured isomeric yield ratios using spin dependent statistical model analysis. It was seen that angular momentum of132I increases with increase of excitation energy and angular momentum of the fissioning nucleus. Comparison of the present data on132I in238U(α,f) with the literature data for the same product in238U(p, f) and238U(γ, f) at various excitation energies show that fragment angular momentum strongly depends on the input angular momentum in the range of excitation energy considered. Experimental fragment angular momentum at all excitation energies were seen to be in agreement with the theoretical values calculated based on thermal equilibration of the various collective rotational degrees after considering the occurence of multichance fission. Thus, strong effect of input angular momentum as well as the statistical equilibration among the various collective rotational degrees of freedom in medium energy fission is corroborated.