Isomeric Level Research Articles

Beta decay of the fission product 125Sb and a new complete evaluation of absolute gamma ray transition intensities

The radionuclide 125Sb is a long-lived fission product, which decays to 125Te by negative beta emission with a half-life of 1008 day. The beta decay is followed by the emission of several gamma radiations, ranging from low to medium energy, that can suitably be used for high-resolution detector calibrations, decay heat calculations and in many other applications. In this work, the beta decay of 125Sb has been studied in detail. The complete published experimental data of relative gamma ray intensities in the beta decay of the radionuclide 125Sb has been compiled. The consistency analysis was performed and discrepancies found at several gamma ray energies. Evaluation of the discrepant data was carried out using Normalized Residual and RAJEVAL methods. The decay scheme balance was carried out using beta branching ratios, internal conversion coefficients, populating and depopulating gamma transitions to 125Te levels. The work has resulted in the consistent conversion factor equal to 29.59(13) %, and determined a new evaluated set of the absolute gamma ray emission probabilities. The work has also shown 22.99% of the delayed intensity fraction as outgoing from the 58 d isomeric 144keV energy level and 77.01% of the prompt intensity fraction reaching to the ground state from the other excited states. The results are discussed and compared with previous evaluations. The present work includes additional experimental data sets which were not included in the previous evaluations. A new set of recommended relative and absolute gamma ray emission probabilities is presented.

First observation of high spin states and isomeric decay in210Fr

The first observation of the prompt and the delayed $\ensuremath{\gamma}$ transitions involving the high spin states in ${}^{210}$Fr is reported. The decay of the high spin states and the isomeric levels of ${}^{210}$Fr, identified for the first time from the known sequence of low-lying transitions found earlier in the $\ensuremath{\alpha}$ decay of ${}^{214}$Ac, were studied. High spin states of the doubly-odd ${}^{210}$Fr, which were produced by the fusion evaporation reaction ${}^{197}$Au (${}^{16}$O, $xn$) ${}^{213\ensuremath{-}x}$Fr, were populated and the subsequent emitted $\ensuremath{\gamma}$ rays were detected through the high-sensitivity germanium clover detector array INGA. The level scheme up to yrast levels of 5.3 MeV excitation energy and $\ensuremath{\sim}20\ensuremath{\hbar}$ angular momentum could be established for the first time through $\ensuremath{\gamma}\ensuremath{\gamma}$, $\ensuremath{\gamma}\ensuremath{\gamma}\ensuremath{\Delta}T$ coincidence, and DCO ratio measurements. A new low-lying isomeric transition at ${E}_{\ensuremath{\gamma}}=$ 203(2) keV was observed. The half-life was measured to be ${T}_{1/2}=$ 41(2) ns. The measured half-life was compared with the corresponding single-particle estimate, based on the level scheme obtained from the experiment.

β-decay measurements forN>40Mn nuclei and inference of collectivity for neutron-rich Fe isotopes

A decay spectroscopic study of the neutron-rich isotopes has been performed using fragmentation of a 86Kr primary beam. Fragments from this reaction have been selected by the LISE2000 spectrometer at the Grand Acc el erateur National d Ions Lourds (GANIL). Half-lives of 29 isotopes, including the first ones identified for 61Ti (15 4 ms), 64V (19 8 ms), and 71Fe (28 5 ms), have been determined and compared with model predictions. 67,68Mn -delayed rays were observed for the first time. The branching for the -delayed neutron emission was measured to be greater than 10(5)% in the 67Mn decay. The 67Fe isomeric level is firmly determined at higher energy than assigned in previous works. The excitation energies of the first (2+) and (4+) states of 68Fe are suggested to lie at 522(1) and 1389(1) keV, respectively, thus bringing confirmation of assignments based on in-beam -ray spectroscopy. Beyond-mean-field calculations with the Gogny D1S force have been performed for even-mass nuclei through the Fe isotopic chain. Not only 68Fe but most of the neutron-rich Fe isotopes with neutron numbers below N = 50 are interpreted as soft rotors. The calculated mean occupancy of the neutron g9/2 and d5/2 orbitals in correlated ground statesmore » is steadily growing with increasing neutron number throughout the isotopic chain. Interpretation of 67Fe data is based upon the present calculations for the 66Fe and 68Fe even cores.« less

Internal electron conversion of the isomeric 57Fe nucleus state with an energy of 14.4 keV excited by the radiation of the plasma of a high-power femtosecond laser pulse

We recorded the spectrum of delayed secondary electrons ejected from the target, which was coated with a layer of iron enriched with the 57Fe isotope to 98%, under its irradiation by fluxes of broadband X-ray radiation and fast electrons from the plasma produced by a femtosecond laser pulse at an intensity of 1017 W cm-2. Maxima were identified at energies of 5.6, 7.2, and 13.6 keV in the spectrum obtained for a delay of 90 — 120 ns. The two last-listed maxima owe their origin to the internal electron conversion of the isomeric level with an energy of 14.4 keV and a lifetime of 98 ns to the K and L shells of atomic iron, respectively; the first-named level arises from a cascade K — L2L3 Auger process. Photoexcitaion by the X-ray plasma radiation is shown to be the principal channel of the isomeric level excitation.

CALCULATION OF 8+ ISOMERS OF EVEN-EVEN NUCLEI 76 NI TO 94 PD FOR N=48 NEUTRONS

Study of the properties of nuclear isomers is a current research focus. We have studied the systematic 8+ isomeric levels, half-lives, deformation parameters, and reduced transition probabilities between 8+ ? 6+ state of even-even 76Ni to 94Pd nuclei for N = 48 neutrons. The calculated half-lives and quadrupole moments are compared with the experimental values. Moreover, we have studied the systematic B (E2) values, intrinsic quadrupole moments and values of s/s2SPas a function of atomic number (Z) for N = 48 neutrons.

Production of the mercury-197 through proton induced reaction on gold

The excitation function of the proton exchange reactions on gold was investigated in the energy range from threshold up to 20MeV. We presented our experimental results upto 14MeV stacked-foil technique was used, the target was of high purity gold foils (99.99%.) Reactions cross-sections and excitation functions were studied. Both isomeric level cross sections of (197)Hg were measured and calculated theoretically using the DDHMS routine of the EMPIRE-II (v2.19) code. Isomeric cross-section ratios for the pair (197m,g)Hg were calculated and presented as a function of proton energy.

Low-lying isomeric levels inCu75

Isomeric low-lying states were identified and investigated in the {sup 75}Cu nucleus. Two states at 61.8(5)- and 128.3(7)-keV excitation energies with half-lives of 370(40)- and 170(15)-ns were assigned as {sup 75m1}Cu and {sup 75m2}Cu, respectively. The measured half-lives combined with the recent spin assignment of the ground state allow one to deduce tentatively spin and parity of the two isomers and the dominant multipolarities of the isomeric transitions with respect to the systematics of the Cu isotopes. Shell-model calculations using an up-to-date effective interaction reproduce the evolution of the 1/2{sup -}, 3/2{sup -}, and 5/2{sup -} states for the neutron-rich odd-mass Cu isotopes when filling the nug{sub 9/2}. The results indicate a significant change in the nuclear structure in this region, where a single-particle 5/2{sup -} state coexists with more and more collective 3/2{sup -} and 1/2{sup -} levels at low excitation energies.

Structures ofPo201andRn205from EC/β+-decay studies

Several low-lying excited states in {sub 86}{sup 205}Rn{sub 119} and {sub 84}{sup 201}Po{sub 117} were identified for the first time following EC/{beta}{sup +} decay of {sup 205}Fr and {sup 201}At, respectively, using {gamma}-ray and conversion electron spectroscopy at the CERN isotope separator on-line (ISOLDE) facility. The EC/{beta}{sup +} branch from {sup 205}Fr was measured to be 1.5(2)%. The excited states of the daughter nuclei are understood in terms of the odd nucleon coupling to the neighboring even-even core. The neutron single-particle energies of the p{sub 3/2} orbital relative to the f{sub 5/2} ground state in {sup 205}Rn, and the f{sub 5/2} orbital relative to the p{sub 3/2} ground state in {sup 201}Po, were determined to be 31.4(2) and 5.7(3) keV, respectively. We tentatively identify a (13/2){sup +} isomeric level at 657.1(5) keV in {sup 205}Rn. The systematic behavior of the (13/2){sup +} and (3/2){sup -} levels is also discussed.

Isomerization in the CDR2 of a monoclonal antibody: Binding analysis and factors that influence the isomerization rate

Isomerization of a monoclonal antibody is one of the common routes of protein degradation. An isomerization in the complementarity-determining region (CDR) was found previously and is investigated in depth in this work. Affinity analysis proves that the antibody with one isomerized heavy chain has lower binding. Binding constants were determined, and exhibited a slower on-rate in conjunction with a faster off-rate for this isomerization. To determine the role of the buffer on the rate of isomerization, this antibody was incubated in various matrices and the amount of isomerized antibody was determined by hydrophobic interaction chromatography (HIC). The rate was found to be dependent on the pH as well as the net negative charge of the buffer components that can act as proton acceptors. An Arrhenius plot was performed to predict the levels of isomerization and a comparison of real samples proved the model was correct. This work affirms that isomerization in the CDR of a therapeutic antibody is important to monitor and the formulation buffer plays a significant role in the rate of the isomerization.

Identification and measurement of isoaspartic acid formation in the complementarity determining region of a fully human monoclonal antibody

Isomerization plays a key role in protein degradation. This isomerization is often difficult to detect by many protein characterization methods such as SDS-PAGE, SEC, and IEF. This work shows the identification of an isomerized aspartic acid residue in the CDR2 of the heavy chain of a fully human monoclonal antibody. This isoaspartic acid increases significantly with storage at 2–8 °C. Hydrophobic interaction chromatography was utilized to separate the isoaspartic variant in the intact state. Mass spectrometry including peptide mapping was employed to identify and confirm the exact location of the modification. Since this modification occurs in the complementarity determining region (CDR) it was found that binding is reduced. Therefore, three different analytical methods for regular analysis of this isomerization are evaluated. These methods include peptide mapping by LC–MS, HIC, and a protein isoaspartate methyltransferase assay. It was determined that HIC is the best method to regularly assay the level of isomerization in this monoclonal antibody.

The11/2−[505]neutron extruder orbital inSm159

Excited states in $^{159}\mathrm{Sm}$, populated following the spontaneous fission of $^{252}\mathrm{Cf}$ have been studied by means of $\ensuremath{\gamma}$ spectroscopy, using the Gammasphere array. In $^{159}\mathrm{Sm}$ we have identified an isomeric level with a half-life of ${T}_{1/2}=116(8)$ ns at an excitation energy of 1276.8 keV and observed a rotational band on top of this isomer. On the basis of the observed properties of the isomer and the band on top of it we propose that the 1276.8-keV level in $^{159}\mathrm{Sm}$ corresponds to the $11/{2}^{\ensuremath{-}}[505]$ neutron extruder configuration. The new excitation scheme of $^{159}\mathrm{Sm}$ is compared to quasiparticle rotor model calculations.

Quantum optimal control of isomerization dynamics of a one-dimensional reaction-path model dominated by a competing dissociation channel

Quantum wave packet optimal control simulations with intense laser pulses have been carried out for studying molecular isomerization dynamics of a one-dimensional (1D) reaction-path model involving a dominant competing dissociation channel. The 1D intrinsic reaction coordinate model mimics the ozone open --> cyclic ring isomerization along the minimum energy path that successively connects the ozone cyclic ring minimum, the transition state (TS), the open (global) minimum, and the dissociative O(2) + O asymptote on the O(3) ground-state (1)A(') potential energy surface. Energetically, the cyclic ring isomer, the TS barrier, and the O(2) + O dissociation channel lie at approximately 0.05, approximately 0.086, and approximately 0.037 hartree above the open isomer, respectively. The molecular orientation of the modeled ozone is held constant with respect to the laser-field polarization and several optimal fields are found that all produce nearly perfect isomerization. The optimal control fields are characterized by distinctive high temporal peaks as well as low frequency components, thereby enabling abrupt transfer of the time-dependent wave packet over the TS from the open minimum to the targeted ring minimum. The quick transition of the ozone wave packet avoids detrimental leakage into the competing O(2) + O channel. It is possible to obtain weaker optimal laser fields, resulting in slower transfer of the wave packets over the TS, when a reduced level of isomerization is satisfactory.

Thermal equilibration ofLu176viaKmixing

In astrophysical environments, the long-lived (${T}_{1/2}=37.6$ Gyr) ground state of $^{176}\mathrm{Lu}$ can communicate with a short-lived (${T}_{1/2}=3.664$ h) isomeric level through thermal excitations. Thus, the lifetime of $^{176}\mathrm{Lu}$ in an astrophysical environment can be quite different than in the laboratory. We examine the possibility that the rate of equilibration can be enhanced via $K$ mixing of two levels near ${E}_{x}=725$ keV and estimate the relevant $\ensuremath{\gamma}$-decay rates. We use this result to illustrate the effect of $K$ mixing on the effective stellar half-life. We also present a network calculation that includes the equilibrating transitions allowed by $K$ mixing. Even a small amount of $K$ mixing will decrease the timescale for equilibration during an $s$-process triggered by the $^{22}\mathrm{Ne}$ neutron source.

Nuclear Data Sheets for A = 187

Evaluated spectroscopic data and level schemes from radioactive decay and nuclear reaction studies are presented for 187Hf, 187Ta, 187W, 187Re, 187Os, 187Ir, 187Pt, 187Au, 187Hg, 187Tl, 187Pb, 187Bi, and 187Po. This evaluation for A = 187 supersedes the earlier one by R.B. Firestone (1991Fi02) published in Nuclear Data Sheets 62, 159 (1991) and the 187Tl evaluation by C.M. Baglin (1999Ba24) published in Nuclear Data Sheets 86, 487 (1999). Highlights of this publication are the following: This evaluation includes first identifications of 187Hf, 187Ta (1999Be63, 2000PoZY) and 187Po (2006An11) nuclides. A B(E2)↑ = 0.080 12 was determined by 1967Bi10 for the 9/2+ state at 845 keV in 187Re Coulomb Excitation. Using this B(E2) value and the adopted 845γ ray properties, a T 1 / 2 = 54 fs 34 can be deduced for the 845 keV level of 187Re. This T 1/2 yields a large B(E2)(W.u.) ≈ 1.3 × 105 for the 263γ (depopulating the same level) indicating either substantial unobserved feeding or incorrect g-ray branching intensities of this level. The decay of g.s. and isomer of 187Tl are poorly known (please see 187Tl ε decay (51 s+15.60 s)). Based on 191Po α decay studies, 2002An19 establishes a 187Pb isomeric level energy at 2(15) keV and assigns J π = 13 / 2 + for the 187Pb g.s. and J π = 3 / 2 − for the isomeric state (inverse of the systematics of odd-mass Pb nuclei in this region). From 187Pb and 187Pb m mass measurements, 2005We11 determined the isomeric level energy at 33(13) keV.

SUGAR-DEPENDENT6 Encodes a Mitochondrial Flavin Adenine Dinucleotide-Dependent Glycerol-3-P Dehydrogenase, Which Is Required for Glycerol Catabolism and Postgerminative Seedling Growth in Arabidopsis

The aim of this study was to clone and characterize the SUGAR-DEPENDENT6 (SDP6) gene, which is essential for postgerminative growth in Arabidopsis (Arabidopsis thaliana). Mutant alleles of sdp6 were able to break down triacylglycerol following seed germination but failed to accumulate soluble sugars, suggesting that they had a defect in gluconeogenesis. Map-based cloning of SDP6 revealed that it encodes a mitochondrial flavin adenine dinucleotide (FAD)-dependent glycerol-3-P (G3P) dehydrogenase:ubiquinone oxidoreductase called FAD-GPDH. This gene has previously been proposed to play a role both in the break down of glycerol (derived from triacylglycerol) and in NAD(+)/NADH homeostasis. Germinated seeds of sdp6 were severely impaired in the metabolism of [U-(14)C]glycerol to CO(2) and accumulated high levels of G3P. These data suggest that SDP6 is essential for glycerol catabolism. The activity of the glycolytic enzyme phosphoglucose isomerase is competitively inhibited by G3P in vitro. We show that phosphoglucose isomerase is likely to be inhibited in vivo because there is a 6-fold reduction in the transfer of (14)C-label into the opposing hexosyl moiety of sucrose when [U-(14)C]glucose or [U-(14)C]fructose is fed to sdp6 seedlings. A block in gluconeogenesis, at the level of hexose phosphate isomerization, would account for the arrested seedling growth phenotype of sdp6 and explain its rescue by sucrose and glucose but not by fructose. Measurements of NAD(+) and NADH levels in sdp6 seedlings also suggest that NAD(+)/NADH homeostasis is altered, and this observation is consistent with the hypothesis that SDP6 participates in a mitochondrial G3P shuttle by cooperating with the cytosolic NAD-dependent GPDH protein GPDHC1.

Onset of isomers inCd125,126,127,128and weakened neutron-neutron interaction strength

The presence of isomeric levels with half-lives in the microsecond range has been identified in $^{125,126,127,128}\mathrm{Cd}$. Neutron-rich Cd isotopes were produced from the fragmentation of a 120 MeV/nucleon $^{136}\mathrm{Xe}$ beam and uniquely identified through their time-of-flight, energy loss, and total kinetic energy. \ensuremath{\gamma} rays from these isomeric levels were measured with an array of Ge detectors that were gated for 15 \ensuremath{\mu}s by a particle implantation trigger from a stack of Si detectors. The \ensuremath{\gamma} rays observed in the decay of $^{126,128}\mathrm{Cd}$ isomers populate low-energy levels previously identified in the \ensuremath{\beta} decay of $^{126,128}\mathrm{Ag}$. The \ensuremath{\gamma} rays found in the decay of $^{125,127}\mathrm{Cd}$ isomers are consistent with expected yrast structures observed in lighter, odd-mass Cd isotopes. The appearance of these isomers at the point where $N/Z$ exceeds 1.6 is interpreted as an indication of the onset of a weakened neutron-neutron interaction that has been proposed for $^{134}\mathrm{Sn}$, whose $N/Z$ also exceeds 1.6.

First observation of excited states in theI138nucleus

Excited states in the $^{138}\mathrm{I}$ nucleus, including ${T}_{1/2}=1.3$ $\ensuremath{\mu}s$ isomer decaying by a stretched $E2$ transition of 68 keV, were observed for the first time. The $^{138}\mathrm{I}$ nucleus was populated in the spontaneous fission of $^{248}\mathrm{Cm}$ and studied by means of prompt \ensuremath{\gamma}-ray spectroscopy using the EUROGAM 2 array. The microsecond isomer was populated in the neutron-induced fission of $^{235}\mathrm{U}$ and observed at the LOHENGRIN separator. Excitation scheme consists of a low-spin part and a medium-spin, $\ensuremath{\Delta}I=1$, band based on the ${7}^{\ensuremath{-}}$ state with the $(\ensuremath{\pi}{g}_{7/2}\ensuremath{\nu}{f}_{7/2}){}_{{7}^{\ensuremath{-}}}$ dominating configuration, as predicted by the shell model. The shell-model calculations of $^{138}\mathrm{I}$ provide the optimum reproduction of the experimental scheme when the $\ensuremath{\pi}{d}_{5/2}$ orbital is lowered by 600 keV relative to its position in $^{133}\mathrm{Sb}$. In the calculation the isomeric level has spin and parity ${3}^{\ensuremath{-}}$ and deexcites by an $E2$ isomeric transition to the ${1}^{\ensuremath{-}}$ level, located only 9 keV above the predicted ${0}^{\ensuremath{-}}$ ground state. Considering additional information on the ground-state spin from the literature, we propose that in $^{138}\mathrm{I}$ the ${1}^{\ensuremath{-}}$ level corresponds to the ground state and the ${0}^{\ensuremath{-}}$ is located above. We note, however, that additional measurements are required to resolve this problem.

First isomeric quadrupole moment measured in fragmentation reactions: The case ofFe61m(9/2+)

This paper demonstrates the feasibility of quadrupole moment measurements on isomeric levels populated in projectile fragmentation reactions. The neutron-rich $^{61}\mathrm{Fe}$$(9/{2}^{+})$ [${E}^{*}=$ 861 keV, ${T}_{1/2}=$ 239(5) ns] isomer was produced and spin aligned by the intermediate energy fragmentation of a $^{64}\mathrm{Ni}$ beam and implanted in a Cd single crystal. Its spectroscopic quadrupole moment $|{Q}_{s}|=41(6)\phantom{\rule{0.3em}{0ex}}e\phantom{\rule{0.3em}{0ex}}{\mathrm{fm}}^{2}$ agrees with mean-field based calculations using the finite-range Gogny force, suggesting a moderately deformed shape characterized by an intrinsic charge quadrupole moment ${Q}_{0}=\ensuremath{-}85\phantom{\rule{0.3em}{0ex}}e\phantom{\rule{0.3em}{0ex}}{\mathrm{fm}}^{2}$ or ${Q}_{0}=+115\phantom{\rule{0.3em}{0ex}}e\phantom{\rule{0.3em}{0ex}}{\mathrm{fm}}^{2}$. The present measurement paves the way for future determinations of isomeric quadrupole moments in more exotic nuclei.

Proline Isomerization of Histone H3 Regulates Lysine Methylation and Gene Expression

The cis-trans isomerization of proline serves as a regulatory switch in signaling pathways. We identify the proline isomerase Fpr4, a member of the FK506 binding protein family in Saccharomyces cerevisiae, as an enzyme which binds the amino-terminal tail of histones H3 and H4 and catalyses the isomerization of H3 proline P30 and P38 in vitro. We show that P38 is necessary for methylation of K36 and that isomerization by Fpr4 inhibits the ability of Set2 to methylate H3 K36 in vitro. These results suggest that the conformational state of P38, controlled by Fpr4, is important for methylation of H3K36 by Set2. Consistent with such an antagonistic role, abrogation of Fpr4 catalytic activity in vivo results in increased levels of H3K36 methylation and delayed transcriptional induction kinetics of specific genes in yeast. These results identify proline isomerization as a novel noncovalent histone modification that regulates transcription and provides evidence for crosstalk between histone lysine methylation and proline isomerization.

Spectroscopy ofNb90at high spin

Excited states of $^{90}\mathrm{Nb}$ were investigated via prompt and delayed \ensuremath{\gamma} decays and the recoil-isomer tagging technique. The level scheme of $^{90}\mathrm{Nb}$ has been extended up to $J=19\ensuremath{\hbar}$ and ${E}_{x}=8.4$ MeV. Half-lives of the ${11}^{\ensuremath{-}}$ and $17/{2}^{\ensuremath{-}}$ isomeric levels in $^{90,91}\mathrm{Nb}$ were measured to be $0.47\ifmmode\pm\else\textpm\fi{}0.01$ and $3.3\ifmmode\pm\else\textpm\fi{}0.4$ \ensuremath{\mu}s, respectively. The results are compared with the predictions of large-basis shell model calculations. The effects of truncation of the valence model space on the calculated results are discussed.