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High-spin states of $^{38}\mathrm{K}$ above the $31.67\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{s}$ (${\ensuremath{\tau}}_{m}$) isomer, populated through the $^{12}\mathrm{C}(^{28}\mathrm{Si},\phantom{\rule{0.16em}{0ex}}np)^{38}\mathrm{K}$ reaction with a 110 MeV $^{28}\mathrm{Si}$ beam, have been studied by using the Indian National Gamma Array (INGA) facility. Two new levels and four new transitions have been added to the existing level scheme. The spins and parities of most of the levels above the isomer have been assigned, modified, and confirmed from ${R}_{\mathrm{DCO}}$, ${R}_{\mathrm{ADO}}$, and linear polarization measurements. The multipole mixing ratios ($\ensuremath{\delta}$) for a few transitions have been measured. Large-basis shell-model calculations have been performed to understand the microscopic origin of these levels. In our calculations, different particle restrictions in $sd$- and $pf$-shell orbitals were used to reproduce the experimental level energies. Two-nucleon transfer spectroscopic factors have also been calculated for the levels above the isomer to support the new spin and parity assignments. Prediction of collective excitation at high excitation energy in $^{38}\mathrm{K}$ is also discussed.

The slowest reaction in the CNO cycle $^{14}\mathrm{N}(p,\ensuremath{\gamma})^{15}\mathrm{O}$ has been studied by populating the ${E}_{p}^{\mathrm{lab}}=278$ keV (${E}_{\mathrm{c}.\mathrm{m}.}^{r}=259$ keV) proton capture resonant state of $^{15}\mathrm{O}$ at 7556 keV. The strength of the resonance ($\ensuremath{\omega}\ensuremath{\gamma}$) has been determined from the experimental data. The level lifetime of the subthreshold resonant state at ${E}_{x}=6792$ keV, as well as the lifetimes of the 5181 keV and 6172 keV states, have been measured using the Doppler shift attenuation method (DSAM). The structural properties of the nucleus $^{15}\mathrm{O}$, such as the level energies, transition strengths, level lifetimes, and spectroscopic factors, have been calculated theoretically by using the large basis shell model, which agrees reasonably well with the present as well as the previous experimental data.

High spin states of $^{37}\mathrm{Ar}$, populated through the $^{27}\mathrm{Al}(^{12}\mathrm{C},np)^{37}\mathrm{Ar}$ reaction with a 40 MeV $^{12}\mathrm{C}$ beam, were studied using the Indian National Gamma Array (INGA) facility. The existing level scheme has been extended up to 10.5 MeV by adding some new levels and transitions. The spins and parities of the new levels were assigned from ${R}_{\mathrm{DCO}}$, ${R}_{\mathrm{ADO}}$, and linear polarization measurements. The spins and parities of the existing levels also were modified or confirmed in the present experiment. The multipole mixing ratios ($\ensuremath{\delta}$) for most of the transitions were measured and compared with the earlier measurements wherever available. Large basis shell model calculations with different particle restrictions in $sd$ and $pf$ orbitals were performed to understand the microscopic origin of these levels. A simple two-level mixing calculation was also performed to extract the amount of multiparticle multihole configuration mixing for a few levels.

An implanted target (14N on Ta) is prepared and characterized via surface and bulk characterization processes. The depth profile of the implanted ions is obtained experimentally by populating a narrow resonance state of15O through14N(ρ,γ) reaction induced with a laboratory proton energy of 278 keV. The experimental profile is then compared with devoted simulations to under- stand the locations of the implantated ions in the lattice structure. Later, the lifetimes of a few excited states of15O, relevant for applications in astrophys- ical scenario, have been determined using Doppler Shift Attenuation Method(DSAM).

Time-stamped data have been used to estimate the decay half-lives of radioactive 118mSb and 64,66,68Ga nuclei. These nuclei are populated through the reaction 4He (Elab = 32 MeV) + nat In and p (Elab = 10 MeV) + natZn, respectively. The g -rays emitted by the excited daughter nuclei are detected by a single high purity germanium (HPGe) detector and the data are acquired using a CAEN 5780M desktop digitizer. Half-lives of different orders of magnitudes for the above mentioned nuclei are obtained from both the decay of parent and the growth of daughter nuclei. It is observed that the half-lives obtained from both these techniques match fairly well and also are consistent with the reported values. It is demonstrated that the time-stamped data can be useful while studying certain half-lives which are too long for measurement using in-beam electronic technique and too short for decay studies in off-beam methods. The data also have a special relevance for constant monitoring of beam current and beam-tuning., 13 Pages, 4 figures

The low-lying states of 117,118Sn have been studied from the decay of 117 g , 118 m Sb, and 117 m Sn. These long-lived species were populated through the reaction 4He + n a t In at E l a b = 32 MeV. Singles, as well as γ-γ coincidence data, were acquired. The uncertainties in the placement of some of the γ-rays in the excitation spectra of 118Sn observed by previous workers have been removed. A γ-ray (984 keV) previously assigned to 118Sn has been eliminated from the level scheme, based on the present analysis. The decay half-lives of 117 g , 118 m Sb have been remeasured. The slope method and deconvolution technique have been used to determine the half-lives of a few isomeric states in 117,118Sn. The results are interpreted in the framework of large scale shell model calculations performed in the 50 - 82 valence shell using truncations. Although the excitation energies were not reproduced well, the theoretical calculations could reasonably reproduce the isomers' transition probabilities due to their nearly pure configuration.

High spin states of 49V populated through 48Ti(4He, 2np)49V reaction with 48 MeV 4He beam, have been studied using the Indian National Gamma Array (INGA) facility. The relative intensities, RDCO and polarization measurements have been carried out for a few transitions in 49V. The level lifetimes have been extracted for a few negative parity yrast levels using Doppler shift attenuation method. Large basis shell model calculations have been performed to understand the microscopic structure of these levels.

An electrically cooled Broad Energy Germanium (BEGe) detector has been characterized in the energy range E γ ∼ 0 . 122 - 7 MeV by utilizing the γ -rays emitted by a short-lived resonance state in 15O populated through 14N(p, γ ) reaction and standard radioactive source (152Eu). The experimental results have been reproduced through simulations with GEANT4 code, including vendor specified detector geometry along with the detailed construction of the target holder flange, to delineate the effects of the holder at various energies and detector position. Later the efficiency with a bare point source has been simulated. It has been found that the electrically cooled BEGe detector is suitable for usage in the γ -ray spectroscopy as well as for the study of resonance phenomena in nuclear astrophysics.

Background: Earlier measurements of fission lifetimes of the highly excited uraniumlike nuclei by K x-ray fluorescence and crystal blocking techniques obtained slow fission (fission time $\ensuremath{\sim}{10}^{\ensuremath{-}18}\phantom{\rule{0.16em}{0ex}}\mathrm{s}$) for most of the fission events and were shown to be incompatible with the very short fission time ($\ensuremath{\sim}{10}^{\ensuremath{-}20}\phantom{\rule{0.16em}{0ex}}\mathrm{s}$) obtained by the nuclear techniques and also with the very small (\ensuremath{\le}5%) percentage of such slow fission events predicted by simple statistical models. One weakness of the earlier fluorescence experiments is that the observed K x-ray peaks were very broad [full width at half maximum $(\mathrm{FWHM})\ensuremath{\approx}15\phantom{\rule{0.16em}{0ex}}\mathrm{keV}$] and the precise energies of the relevant K x-ray lines could not be determined from such measurements.Purpose: The purpose is to look at the relevant K x-ray energy region in coincidence with the fission fragments with a high resolution (\ensuremath{\approx}1 keV) spectrometer to obtain evidence of slow fission and determine its percentage.Method: Highly excited plutonium nuclei were produced in the fusion of $^{4}\mathrm{He}+^{238}\mathrm{U}$ at $E{(^{4}\mathrm{He})}_{\mathrm{Lab}}=60\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}$. The intrinsic width of plutonium K x-ray lines in coincidence with the fission fragments was determined as a direct measure (or lower limit) of the fission time of the slow ($\ensuremath{\sim}{10}^{\ensuremath{-}18}\phantom{\rule{0.16em}{0ex}}\mathrm{s}$) fission events. The minimum percentage of slow fission events has been determined from the K x-ray multiplicity per fission event and the probability of creation of K-orbital vacancies in plutonium.Results: A narrow peak (FWHM \ensuremath{\approx} 1 keV) observed in the coincidence photon spectrum at (102.8 \ifmmode\pm\else\textpm\fi{} 0.5) keV, just below the characteristic plutonium ${K}_{\ensuremath{\alpha}1}$ line (103.7 keV) has been attributed to the plutonium ${K}_{\ensuremath{\alpha}1}$ line on the basis of supporting evidence and calculations and we deduce that most of the fission events are slow (fission time $g{10}^{\ensuremath{-}18}\phantom{\rule{0.16em}{0ex}}\mathrm{s}$). No peak has been observed exactly at 103.7 keV.Conclusions: The shift [(0.9 \ifmmode\pm\else\textpm\fi{} 0.5) keV] of plutonium K x-ray lines is plausible, if the fissioning plutonium nucleus spends most of its long fission time in a highly deformed dumbbell shape (beyond saddle) and the corresponding results are in agreement with those obtained earlier by the atomic techniques. Alternatively, if no significant shift of plutonium K x-ray lines can be expected, the absence of a peak at 103.7 keV contradicts earlier atomic technique claims of a significant percentage of slow fission events.

The present Rapid Communication reports conclusive evidence for an antimagnetic rotational band in the odd-odd $^{142}\mathrm{Eu}$ nucleus. The parity of the states of a quadrupole sequence in this nucleus is identified firmly from polarization measurements using the Indian National Gamma Array, and lifetimes of some of the states in the same structure are measured using the Doppler-shift attenuation method. The decreasing trends of the deduced quadrupole transition strength $B(E2)$ with spin in the sequence along with the increasing ${J}^{(2)}/B(E2)$ values conclusively establish the origin of these states as arising from antimagnetic rotation. The results are well reproduced by numerical calculations within the framework of a semiclassical geometric model.

The high-spin states in $^{153}\text{Ho}$ have been studied by the $_{\phantom{\rule{4pt}{0ex}}57}^{139}\text{La}(^{20}\text{Ne},6n)$ reaction at a projectile energy of 139 MeV at the Variable Energy Cyclotron Centre (VECC), Kolkata, India, utilizing an earlier campaign of the Indian National Gamma Array (INGA) setup. Data from $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coincidence, directional correlation, and polarization measurements have been analyzed to assign and confirm the spins and parities of the levels. We have suggested a few additions and revisions of the reported level scheme of $^{153}\text{Ho}$. The RF-$\ensuremath{\gamma}$ time difference spectra have been useful to confirm the half-life of an isomer in this nucleus. From the comparison of experimental and theoretical results, it is found that there are definite indications of shape coexistence in this nucleus. The experimental and calculated lifetimes of several isomers have been compared to follow the coexistence and evolution of shape with increasing spin.

Graphical abstract: New microstructural analysis and phase transition of rare earth doped mixed oxide compounds such as: Sm{sub 2−x}Dy{sub x}Zr{sub 2}O{sub 7} (where x = 0.0 ≤ x ≥ 2.0) that are potentially useful as solid oxide fuels, ionic conductors, optoelectronic materials and most importantly as radiation resistant host for high level rad-waste disposal, structural transition in the system is reported through positron annihilation spectroscopy as there is an indication in the X-ray diffraction analysis. Highlights: ► Zirconium oxide material doped with rare earth ions. ► The method of positron annihilation spectroscopy suggests a phase transition in the system. ► The crystal structure transformation from pure pyrochlore to defect fluorite type of structure is shown by X-ray diffraction results. -- Abstract: A series of compounds with the general composition Sm{sub 2−x}Dy{sub x}Zr{sub 2}O{sub 7} (where 0 ≤ x ≥ 2.0) were synthesized by chemical route and characterized by powder X-ray diffraction (XRD) analysis. The rare earth ion namely Sm{sup +3} in the compound was gradually replaced with another smaller and heavier ion, Dy{sup +3} of the 4f series, there by resulting in order–disorder structural transition, which has been studied by positron annihilation lifetime and Doppler broadening spectroscopy. This study revealsmore » the subtle electronic micro environmental changes in the pyrochlore lattice (prevalent due to the oxygen vacancy in anti-site defect structure of the compound) toward its transformation to defect fluorite structure as found in Dy{sub 2}Zr{sub 2}O{sub 7}. A comparison of the changes perceived with PAS as compared to XRD analysis is critically assayed.« less

Lifetimes of the states in the quadrupole structure in 143Eu have been measured using the Doppler shift attenuation method as well as parity of the states in the sequence has been firmly identified from polarization measurement using the Indian National Gamma Array. The decreasing trends of the deduced quadrupole transition strength B(E2) with spin, along with increasing J (2) /B(E2) values before band crossing, conclusively establish the origin of these states as arising out of antimagnetic rotation. The abrupt increase in the B(E2) values after the band crossing in the quadrupole band, a novel feature observed in the present experiment, may indicates the crossing of different shears configurations resulting in re-opening of shears structure. The results are well reproduced by numerical calculation within the framework of semi-classical geometric model., Comment: 6 pages, 4 postscript figures

High-spin dipole structures in $^{143}\mathrm{Eu}$ have been studied via the fusion-evaporation $^{116}\mathrm{Cd}$ $(^{31}\mathrm{P}$, $4n)$ reaction at a beam energy of 148 MeV using a clover detector array (Indian National Gamma Array). The parity of the two observed dipole bands has been firmly established from linear polarization measurements. Level lifetimes of these bands have been measured using the Doppler shift attenuation method. The drop in $B(M1)$ values with spin exhibits a clear signature of the magnetic rotational character of these two bands. Configurations were assigned to the bands in the framework of the shears mechanism with the principal axis cranking model calculation. Alignment of an additional proton in the ${h}_{11/2}$ orbital gives rise to the unique observation of a large increase in the $B(M1)$ values for the higher-lying band.

Nuclei in the upper-$sd$ shell usually exhibit characteristics of spherical single particle excitations. In the recent years, employment of sophisticated techniques of gamma spectroscopy has led to observation of high spin states of several nuclei near A$\simeq$ 40. In a few of them multiparticle, multihole rotational states coexist with states of single particle nature. We have studied a few nuclei in this mass region experimentally, using various campaigns of the Indian National Gamma Array setup. We have compared and combined our empirical observations with the large-scale shell model results to interpret the structure of these nuclei. Indication of population of states of large deformation has been found in our data. This gives us an opportunity to investigate the interplay of single particle and collective degrees of freedom in this mass region., Comment: 8 pages, 13 figures, submitted for publication in the Proceedings of "Frontiers in Gamma-Ray Spectroscopy 2012 (FIG12), held at New Delhi, March 5th - 7th, 2012, Organized by Inter University Accelerator Center, New Delhi, India

Medium-spin states in 122Te have been populated using the reaction 116Cd (11B, p4n)122Te at a beam energy of 65MeV and \( \gamma\) -\( \gamma\) coincidences were measured using the INGA spectrometer. The previously known level scheme has been extended to spin \( \sim 23\hbar\) with the observation of the maximally aligned state at spin 22+. The experimental results are compared with the shell model calculations. The configurations of the energy levels and terminating states are discussed.

A superdeformed (SD) band has been identified in a non-$\ensuremath{\alpha}$-conjugate nucleus ${}^{35}\text{Cl}$. It crosses the negative-parity ground band above $11/{2}^{\ensuremath{-}}$ and becomes the yrast at $15/{2}^{\ensuremath{-}}$. Lifetimes of all relevant states have been measured to follow the evolution of collectivity. Enhanced $B(E2)$, $B(E1)$ values as well as energetics provide evidence for superdeformation and existence of parity doublet cluster structure in an odd-$A$ nucleus in the $A\ensuremath{\simeq}40$ region. Large-scale shell-model calculations assign ${(sd)}^{16}{(pf)}^{3}$ as the origin of these states. Calculated spectroscopic factors correlate the SD states in ${}^{35}\text{Cl}$ to those in ${}^{36}\text{Ar}$.

High-spin states in I-122 have been investigated using the Cd-116(B-11,5n)I-122 reaction at a beam energy of 65 MeV and gamma-ray coincidence events were recorded with the INGA spectrometer. The level scheme of I-122 has been extended up to spin I = 30. Experimental features, such as band-crossing frequencies, aligned angular momenta, signature splitting, and B(M1)/B(E2) ratios have been used for configuration assignments to low-energy band structures. Maximally aligned states involving all eight particles outside the Sn-114 core and states with one particle antialigned have been identified. Cranked Nilsson-Strutinsky calculations have been used to interpret high-spin structures.

A low energy photon spectrometer (LEPS), which is a composite planar HPGe, has been characterised experimentally. It has been shown that beyond 200 keV, effect of image charges deteriorates the efficiency of the detector in its addback mode. Data have been corrected on event-by-event basis resulting in improvement of the performance.