DCO Ratios Research Articles

Observation of signature partner bands in Sb117

Rotational band structures and low-lying single-particle levels in $^{117}\mathrm{Sb}$ have been populated using reaction $^{115}\mathrm{In}(\ensuremath{\alpha}$, $2n)^{117}\mathrm{Sb}$ at a beam energy of 28 MeV and investigated using $\ensuremath{\gamma}$-ray spectroscopic techniques. The existing level scheme has been extended with the observation of 31 new transitions. The signature partner of the band structure based on the configuration of $\ensuremath{\pi}{g}_{7/2}\phantom{\rule{4pt}{0ex}}\ensuremath{\bigotimes}\phantom{\rule{4pt}{0ex}}2\mathrm{p}\text{\ensuremath{-}}2\mathrm{h}$ of the $^{116}\mathrm{Sn}$ core has been established in $^{117}\mathrm{Sb}$ for the first time. Several single-particle nonyrast transitions connecting to various band structures have also been identified. Measurements of the DCO ratios, polarization asymmetry and angular distribution of the observed $\ensuremath{\gamma}$ rays have been carried out to assign the spin-parities to the levels of all the band structures and the low-lying single-particle states, populated in the present work. The spin-parities are also determined for the states of the two previously unassigned bands. The lower-spin structures have been interpreted on the basis of large-scale shell-model calculations using OXBASH. Particle Rotor Model (PRM) calculations have been carried out to explain the large signature splitting of the observed signature partner bands.

Exploring the structure of Xe isotopes in A ~ 130 region: Single particle and collective excitations

High and medium spin structures of 130,131Xe have been studied using α-induced fusion-evaporation reaction and the Indian National Gamma Array (INGA) coupled with a digital data acquisition system. Various new band structures and near yrast levels of 131Xe have been established. The multipolarities of the observed transitions have been assigned on the basis of the DCO ratios and the polarization asymmetry measurements. Band structures based on 1-quasi-particle (qp), 3-qp configurations have been observed. A new Magnetic Rotational (MR) band based on 5-qp configuration has also been established in 131Xe. The MR band has been interpreted in terms of shears mechanism with principal axis cranking (SPAC) calculations. Shell Model calculations are carried out to describe the non yrast states of 131Xe above the 11/2− isomer. New excited states have also been identified in 130Xe, produced in the same reaction.

Negative parity three-quasiparticle band in 127I

The excited states of 127I were populated via 124Sn(7Li, 4n $\gamma$ ) fusion-evaporation reaction at $ E_{beam} = 33$ MeV. A strongly coupled $\Delta I = 1$ band has been established above 2423keV state with $J^{\pi} = 19/2^{-}$ as bandhead, likely to be associated with the three-quasiparticle configuration. Spin and parity of these multi-quasiparticle states have been confirmed from DCO ratio and linear polarization asymmetry of depopulating $\gamma$ -rays. The parity of these states have been found altered from their previous assignment.

Yrare low-spin positive-parity states in N = 88 66 154 Dy

Low-spin positive-parity yrare states of 66 154 Dy88 were established using the 155Gd(3He,4n) reaction at a beam energy of $E_{lab} = 37.5$ MeV. The AFRODITE spectrometer array at iThemba LABS was used to record $\gamma\gamma$ coincidences and measure DCO ratios and polarisation asymmetries. The $K^{\pi}=2^{+}$ $ \gamma$ band has been observed up to spin $13^{+}$ in the odd spins and to $ 12^{+}$ in the even spins. The staggering parameter S(I) of the $ \gamma$ band is compared to that found in other N = 88 isotones. Different behaviour of S(I) with increasing spin is observed for each of the isotones. We conjecture that the variation in S(I) is mainly due to mixing of the even-spin states with the same spin and parity states in neighbouring rotational bands. A second $ K^{\pi}=2^{+}$ band has been established up to a spin of $ 12^{+}$ in the even spins. We suggest that this is a $ \gamma$ band based on the $ J^{\pi} = 0^{+}$ state at $ E_{x} = 660.6$ keV.

Revised level structure of 127Xe

Excited states of 127Xe were populated via fusion-evaporation reaction. A level at 2306.7 keV has been established instead of the previously reported two different levels at 2307 keV. has been assigned to this level on the basis of the DCO ratio and linear polarization asymmetry of decaying γ-rays. A weak γ-ray of 840.2 keV, decaying from this state to the state, has also been identified. Results are compared with neighboring Xe isotopes.

High spin spectroscopy and shape evolution inCd105

High spin states in 105Cd were studied using 16O beam on 92Mo reaction at an incident beam energy of 75 MeV. The level scheme of 105Cd has been observed up to an excitation energy of 10.8 MeV with the addition of 30 new gamma transitions to the previous work. Spin and parity for most of the reported levels are assigned from the DCO ratios and linear polarization measurements. The microscopic origin of the investigated band structures is discussed in the context of triaxial projected shell model. The energies of observed positive and negative parity bands agree with the predictions of the TPSM by considering triaxial deformation for the observed excited band structures. The shape evolution with increasing angular momentum is explained in the framework of Cranked Shell Model and the Total Routhian Surface calculations.

Level-scheme investigation of 33S

An angular correlation experiment was carried out for 33 S at Laboratori Nazionali di Legnaro with the gamma-ray detector array GASP. The reaction used was 24Mg(14N,α p)33S at a beam energy of 40MeV. An analysis of DCO ratios and triple gamma coincidences was performed. So far, a new level depopulated by 3 γ -ray transitions has been found and its spin was determined. The work for further extension of the level scheme is in progress.

In-beam γ-ray Spectroscopy of 30P via the 28Si(3He,pγ)30P Reaction

The level structure of 30P up to 8.25 MeV was investigated via in-beam γ-ray spectroscopy using the 28Si(3He,pγ)30P reaction at 9 MeV at the University of Tsukuba Tandem Accelerator Complex in Japan. An energy level scheme was deduced from γ-γ coincidence measurements. 47 new transitions have been observed from the previously known states (mostly resonances), thereby reducing the uncertainties in the excitation energies of 17 states from 3 to 10 keV to values of < 1 keV. Furthermore, spin assignments based on measurements of γ-ray angular distributions and γ-γ directional correlation of oriented nuclei (DCO ratios) were made for several observed levels of 30P.

Spin-parity assignments and extension of the 02+band in158Er

Low and medium spin collective structures in 158 Er have been studied using the 150 Sm(12 C,4nγγ ) fusion-evaporation reaction at a beam energy of E lab = 65 MeV. A band built on the 02 + excitation has been established and extended to J π = 18+ from the analysis of γ -γ coincidence relationships, intensity arguments and DCO ratios. The 02 + band in 158 Er presents a similar trend to the 02 + bands in the lighter N = 90 isotones but lies about 125 keV higher. This systematic trend supports a similar configuration for the 02 + bands in the N = 90 isotones.

Search for two-POV states, excited quintuplets and septuplets in 88–92Sr and 94,96Zr

Excited states in 88,89,90,92Sr are reanalyzed by assigning new spins and parities according to the published DCO ratios (RDCO). Possible candidates for the two-POV 6+ states are proposed in 88,90,92Sr not only based on spins but also by investigating the state energy and E2 transition energy systematics between 96Zr, 146Gd and the neighboring Sr isotopes. Multiple excited states (multiplets) with the same configuration in 88,89Sr are interpreted as the weak coupling of a 2+ one-phonon quadrupole or a 3− one-phonon octupole vibration to the excited 8+ state for 88Sr and a 3− one-phonon octupole vibration to the excited 21/2+ state for 89Sr. The 8+⊗2+ quintuplet and 8+⊗3− multiplet in 88Sr and 8+⊗3− septuplet in 89Sr are reported. Two excited states with the new spins and parities of 10+ and 12 + in 90,92Sr have the configurations of 8+⊗2+ and 8+⊗4+, respectively. Also, 8+⊗2+ quintuplets and 8+⊗3− multiplets are proposed for 94,96Zr.

Nuclear structure of 216 Ra at high spin

High-spin states of 216Ra (\(\emph{Z}=88\), \(\emph{N}=128\)) have been investigated through 209Bi(10B, 3n) reaction at an incident beam energy of 55 MeV and 209Bi(11B, 4n) reaction at incident beam energies ranging from 65 to 78 MeV. Based on γγ coincidence data, the level scheme for 216Ra has been considerably extended up to ~ 33\(\hbar\) spin and 7.2 MeV excitation energy in the present experiment with placement of 28 new γ-transitions over what has been reported earlier. Tentative spin-parity assignments are done for the newly proposed levels on the basis of the DCO ratios corresponding to strong gates. Empirical shell model calculations were carried out to provide an understanding of the underlying nuclear structure.

High spin band structures in doubly odd194Tl

The high-spin states in odd-odd $^{194}$Tl nucleus have been studied by populating them using the $^{185,187}$Re($^{13}$C, xn) reactions at 75 MeV of beam energy. $\gamma-\gamma$ coincidence measurement has been performed using the INGA array with a digital data acquisition system to record the time stamped data. Definite spin-parity assignment of the levels was made from the DCO ratio and the IPDCO ratio measurements. The level scheme of $^{194}$Tl has been extended up to 4.1 MeV in excitation energy including 19 new gamma ray transitions. The $\pi h_{9/2} \otimes \nu i_{13/2}$ band, in the neighboring odd-odd Tl isotopes show very similar properties in both experimental observables and calculated shapes. Two new band structures, with 6-quasiparticle configuration, have been observed for the first time in $^{194}$Tl. One of these bands has the characteristics of a magnetic rotational band. The cranked shell model calculations, using a deformed Woods-Saxon potential, have been performed to obtain the total Routhian surfaces in order to study the shapes of the bands and the band crossing in $^{194}$Tl. The semiclassical formalism has been used to describe the magnetic rotational band.

Quest for Chirality in 107Ag

High spin states in 107Ag have been studied via the 100Mo(11B, 4n)107Ag reaction at a beam energy of 60 MeV on the HI-13 tandem accelerator at the China Institute of Atomic Energy. By analyzing the gamma-gamma coincidence and their DCO ratios, a new level scheme of 107Ag is presented. The structures for the newly constructed bands are briefly discussed and tentatively assigned to be chiral doublet bands.

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.

New band structures in 107Ag

High spin states in 107Ag are studied via the 100Mo(11B, 4n)107 Ag reaction at an incident beam energy of 60 MeV. Prompt γ-γ coincidence and DCO ratios are measured by the detector arrays in CIAE. The level scheme has been updated and a new negative band belonging to 107Ag is identified. The new negative side band has been constructed and its configuration is tentatively assigned to πg9/2 ⊗ νh11/2(g7/2/d5/2).

Effects of suppressing the DNA mismatch repair system on homeologous recombination in tomato

In plant breeding, the ability to manipulate genetic (meiotic) recombination would be beneficial for facilitating gene transfer from wild relatives of crop plants. The DNA mismatch repair (MMR) system helps maintain genetic integrity by correcting base mismatches that arise via DNA synthesis or damage, and antagonizes recombination between homeologous (divergent) DNA sequences. Previous studies have established that the genomes of cultivated tomato (Solanum lycopersicum) and the wild relative S. lycopersicoides are substantially diverged (homeologous) such that recombination between their chromosomes is strongly reduced. Here, we report the effects on homeologous recombination of suppressing endogenous MMR genes in S. lycopersicum via RNAi-induced silencing of SlMSH2 and SlMSH7 or overexpressing dominant negatives of Arabidopsis MSH2 (AtMSH2-DN) in an alien substitution line (SL-8) of S. lycopersicoides in tomato. We show that certain inhibitions of MMR (RNAi of SlMSH7, AtMSH2-DN) are associated with modest increases in homeologous recombination, ranging from 3.8 to 29.2% (average rate of 17.8%) compared to controls. Unexpectedly, only the AtMSH2-DN proteins but not RNAi-induced silencing of MSH2 was found to increase homeologous recombination. The ratio of single to double crossovers (SCO:DCO ratio) decreased by approximately 50% in progeny of the AtMSH2-DN parents. An increase in the frequency of heterozygous SL-8 plants was also observed in the progeny of the SlMSH7-RNAi parents. Our findings may contribute to acceleration of introgression in cultivated tomato.

CHIRALITY IN THE MASS 80 REGION: 79Kr

The high spin states of 79 Kr were studied via the 70 Zn (13 C , 4 n ) reaction to search for chiral doublet bands based on the three-quasi-particle configuration, πg9/22 ⊗ νg9/2-1. The 13 C beam of 65 MeV was provided by the 930 AVF Cyclotron at CYclotron and RadioIsotope Center (CYRIC) facility at Tohoku University. The triple coincidence γ rays were detected by the Hyperball2 array. The side band structure to the πg9/22 ⊗ νg9/2-1 yrast band has been identified in 79 Kr . Spin and parity assignments are made based on the DCO ratio and linear polarization analysis.

Seven-quasiparticle bands inCe139

The high spin states in the $^{139}\mathrm{Ce}$ nucleus have been studied by in-beam $\ensuremath{\gamma}$-spectroscopic techniques using the reaction $^{130}\mathrm{Te}(^{12}\mathrm{C},3n)^{139}\mathrm{Ce}$ at ${E}_{\mathrm{beam}}=65$ MeV. A gamma detector array, consisting of five Compton-suppressed Clover detectors was used for coincidence measurements. 15 new levels have been proposed and 28 new $\ensuremath{\gamma}$ transitions have been assigned to $^{139}\mathrm{Ce}$ on the basis of $\ensuremath{\gamma}\ensuremath{\gamma}$ coincidence data. The level scheme of $^{139}\mathrm{Ce}$ has been extended above the known 70 ns ${\frac{19}{2}}^{\ensuremath{-}}$ isomer up to $~6.1$ MeV in excitation energy and $\frac{35}{2}\ensuremath{\hbar}$ in spin. The spin-parity assignments for most of the newly proposed levels have been made using the deduced Directional Correlation from Oriented states of nuclei (DCO ratio) and the Polarization Directional Correlation from Oriented states (PDCO ratio) for the de-exciting transitions. The observed level structure has been compared with a large basis shell model calculation and also with the predictions from cranked Nilsson-Strutinsky (CNS) calculations. A general consistency has been observed between these two different theoretical approaches.

Multi-quasiparticle bands inCe137

Excited states of $^{137}\mathrm{Ce}$, populated in the $^{130}\mathrm{Te}$(${}^{12}\mathrm{C},5n$) reaction at a beam energy of 65 MeV, have been investigated by $\ensuremath{\gamma}\ensuremath{\gamma}$ coincidence spectroscopy using a modest Clover Ge array. Unique spin-parity assignments have been made for most of the levels at high spin and excitation energy by using DCO ratios and polarization information. The known level scheme of $^{137}\mathrm{Ce}$ has been considerably revised on the basis of the new information. A sequence of $M1$ transitions, developed on the 5379.1-keV $\frac{33}{2}\ensuremath{\hbar}$ level has been suggested to be a positive-parity band through unambiguous assignment of multipolarity of 1124.1- and 836.1-keV \ensuremath{\gamma} rays. Another positive-parity bandlike structure has been seen, starting at the 2928.4-keV ${\frac{19}{2}}^{+}$ level. Total Routhian surface calculations have been done to predict underlying multi-quasiparticle configurations for the observed bands.

Excited States in 207Rn

Excited states in 207Rn are investigated via the196Pt(16O,Sn)207Rn reaction at beam energies from85 to 95 MeV using techniques of in-beam γ-ray spectroscopy.Measurements of γ-ray excitation function, x-γ and γ-γ-tcoincidences are performed with ten BGO(AC)HPGe detectors. Based onthese measurements, a level scheme of 207Rn, including 17 γ-raysand 18 levels, is established. Spins for most of the levels areproposed according to the measured DCO ratios. The level structure iscompared with a weak-coupling calculation using the interactionenergies extracted from neighbouring nuclei.