Ray Transitions Research Articles

Revisiting the decay scheme and half-life of 139Ba

The decay of 139Ba to levels of 139La has been studied employing singles and \( \gamma\) -\( \gamma\) coincidence spectroscopy techniques, using four Compton suppressed Clover detectors. The \( \gamma\) -\( \gamma\) coincidence data obtained in the present work has been more conclusive as compared to the coincidence data obtained using NaI(Tl)-Ge(Li) detectors in the earlier investigations. The relative intensities of twenty-seven \( \gamma\) -ray transitions have been determined. The \( \gamma\) -ray transitions with energies 1044 and 1525keV, attributed to the decay of 139Ba in the previous works, have been found to be due to long-lived impurities. The 1691keV transition, previously assigned to the decay of 139Ba , is found to be mainly associated with an impurity with only a small fraction belonging to 139Ba decay. The half-life of 139Ba has been measured. The present work attempts to resolve some of the discrepancies in the previous investigations, which will be helpful in the precise determination of \( \beta\) -decay scheme of 139Ba.

Hindered decays from a non-yrast four-quasiparticle isomer in164Er

The half-life of a ${K}^{\ensuremath{\pi}}={12}^{+}$ isomer in ${}^{164}$Er has been measured to be 68(2) ns, and new decay pathways have been identified. These include highly $K$-forbidden $\ensuremath{\gamma}$-ray transitions directly to the ground-state rotational band, with reduced hindrance values that can be compared with those found for heavier nuclides. The new data support the interpretation that the level density is a key variable in determining $K$-forbidden transition rates.

Extensiveγ-ray spectroscopy of band structures in3062Zn32

An experimental study of the ${}^{62}$Zn nucleus has been performed by combining the data sets from four fusion-evaporation reaction experiments. Apart from the previously published data, the present results include ten new rotational band structures and two more superdeformed bands. The Gammasphere Ge-detector array in conjunction with the 4$\ensuremath{\pi}$ charged-particle detector array Microball allowed for the detection of $\ensuremath{\gamma}$ rays in coincidence with evaporated light particles. The deduced level scheme includes some 260 excited states, which are connected with more than 450 $\ensuremath{\gamma}$-ray transitions. Spins and parities of the excited states have been determined via directional correlations of $\ensuremath{\gamma}$ rays emitted from oriented states. The experimental characteristics of the rotational bands are analyzed and compared with results from cranked Nilsson-Strutinsky calculations. The present analysis, combined with available experimental results in the $A\ensuremath{\sim}60$ mass region, can be used to improve the current set of Nilsson parameters in the $\mathcal{N}=3$ and $\mathcal{N}=4$ oscillator shells.

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.

Low-Energy Enhancement in the Photon Strength of Mo95

A new experimental technique is presented using proton-γ-γ correlations from (94)Mo(d,p)(95)Mo reactions which allows for the model-independent extraction of the photon strength function at various excitation energies using primary γ-ray decay from the quasicontinuum to individual low-lying levels. Detected particle energies provide the entrance excitation energies into the residual nucleus while γ-ray transitions from low-lying levels specify the discrete states being fed. Results strongly support the existence of the previously reported low-energy enhancement in the photon strength function.

γ-ray spectroscopy of the odd-oddN=Z+2deformed proton emitter112Cs

Gamma-ray transitions have been observed in the proton-emitting $N=Z+2$ (${T}_{z}=1$) isotope ${}^{112}$Cs. The transitions have been unambiguously assigned to ${}^{112}$Cs by correlation with the characteristic proton decay, using the method of recoil-decay tagging with mass selection. The measured proton-decay energy and half-life are ${E}_{p}=810(5)$ keV and ${T}_{1/2}=470(50)$ $\ensuremath{\mu}$s, respectively, which are consistent with previous measurements. Five $\ensuremath{\gamma}$-ray transitions have been observed which appear to form a rotational sequence. The energy differences between excited states in the sequence are consistent with an assignment as the favored signature of the $\ensuremath{\nu}({h}_{11/2})\ensuremath{\bigotimes}\ensuremath{\pi}({h}_{11/2})$ structure. Tentative evidence for fine structure in the ${}^{112}$Cs proton decay is also observed.

Measuring the absolute decay probability of82Sr by ion implantation

We have developed a method of implanted ion counting in order to determine the absolute decay probability of the 776.5 keV $\ensuremath{\gamma}$-ray transition in the decay sequence of ${}^{82}$Sr${\ensuremath{\rightarrow}}^{82}$Rb${\ensuremath{\rightarrow}}^{82}$Kr. A 215 MeV beam of ${}^{82}$Sr was produced at the Holifield Radioactive Ion Beam Facility and passed through an ionization chamber that counted and identified the ions before they were implanted into thin aluminum foils. Subsequent offline measurements using a Ge detector deduced the probability per decay of ${}^{82}$Rb for the 776.5 keV $\ensuremath{\gamma}$ ray in ${}^{82}$Kr to be 0.1493(37), in agreement with the accepted average value of 0.1508(16). This new technique measures directly the number of decaying nuclei in a given sample and significantly reduces the dependence on knowledge of the complete decay level scheme.

Discovery of isomers in dysprosium, holmium, and erbium isotopes withN=94to 97

High-spin states in the ${}_{68}^{164}$Er${}_{96}$ region were studied using ${}^{9}$Be $+$ ${}^{160}$Gd reactions. Pulsed beam conditions were exploited for enhanced sensitivity to delayed $\ensuremath{\gamma}$-ray transitions. New isomers were identified in ${}^{161}$Dy, ${}^{163}$Ho, ${}^{162}$Er, and ${}^{165}$Er. The ${}^{162}$Er isomer is interpreted to decay by $E1$ transitions to the ground-state band with a reduced hindrance of ${f}_{\ensuremath{\nu}}=33$. A plot of ${f}_{\ensuremath{\nu}}$ values for all $\ensuremath{\Delta}K=7$, $E1$ transitions from two-quasiparticle isomers to the ground-state bands of even-even nuclei reveals only a small influence from the dynamic to kinematic moment-of-inertia ratio, which provides a measure of Coriolis $K$ mixing within the ground-state band. This is interpreted to imply that the relatively low hindrances are due to $K$ mixing in the isomer, caused by a combination of Coriolis and octupole band mixing.

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.

High-numerical-aperture microlens shape measurement with digital holographic microscopy

In this Letter, we introduce an algorithm that overcomes limitations in shape measurement by holographic microscopic methods in cases of micro-optical elements with high NA, such as microlenses. The presented algorithm provides a simple method for shape reconstruction from interferometrically measured phase. The algorithm is based on the analysis of local ray transition through the measured object. We develop algorithms for holographic configurations working in transmission and reflection. The accuracy of the developed algorithms is proved by experiments and extensive simulations. We present an experiment in a holographic Mach-Zehnder configuration where we have measured and successfully reconstructed the height distribution of spherical and cylindrical microlenses with NA up to 0.3.

High-spinμs isomeric states in96Ag

The isomeric and {\beta} decays of the N = Z +2 nucleus 96Ag were investigated at NSCL. A cascade of {\gamma}-ray transitions originating from the de-excitation of a {\mu}s isomer was observed for the first time and was found in coincidence with two previously-known transitions with energies of 470 and 667 keV. The isomeric half-life was determined as 1.45(7) {\mu}s, more precise than previously reported. The existence of a second, longer-lived {\mu}s isomer, associated with a 743-keV transition, is also proposed here. Shell model results within the (p_{3/2}p_{1/2}f_{5/2}g_{9/2}) model space, using the jj44b interaction, reproduced level energies and isomeric decay half-lives reasonably well.

In-beamγ-ray spectroscopy ofMg35andNa33

Excited states in the very neutron-rich nuclei $^{35}\mathrm{Mg}$ and $^{33}\mathrm{Na}$ were populated in the fragmentation of a $^{38}\mathrm{Si}$ projectile beam on a Be target at 83 MeV/u beam energy. We report on the first observation of $\ensuremath{\gamma}$-ray transitions in $^{35}\mathrm{Mg}$, the odd-$N$ neighbor of $^{34}\mathrm{Mg}$ and $^{36}\mathrm{Mg}$, which are known to be part of the `island of inversion'' around $N=20$. The results are discussed in the framework of large-scale shell-model calculations. For the $A=3Z$ nucleus $^{33}\mathrm{Na}$, a new $\ensuremath{\gamma}$-ray transition was observed that is suggested to complete the $\ensuremath{\gamma}$-ray cascade $7/{2}^{+}\ensuremath{\rightarrow}5/{2}^{+}\ensuremath{\rightarrow}3/{2}_{\mathit{gs}}^{+}$ connecting three neutron two-particle--two-hole intruder states that are predicted to form a close-to-ideal $K=3/2$ rotational band in the strong-coupling limit.

β-decay studies of the transitional nucleusCu75and the structure ofZn75

The $\ensuremath{\beta}$ decay of $^{75}\mathrm{Cu}$ [${t}_{1/2}=1.222(8)$s] to levels in $^{75}\mathrm{Zn}$ was studied at the Holifield Radioactive Ion Beam Facility of Oak Ridge National Laboratory. The $\ensuremath{\gamma}\ensuremath{\gamma}$ and $\ensuremath{\beta}\ensuremath{\gamma}$ data were collected at the Low-energy Radioactive Ion Beam Spectroscopy Station using the high-resolution isobar separator to obtain a purified $^{75}\mathrm{Cu}$ beam with a rate of over 2000 ions per second. The excited states in $^{75}\mathrm{Zn}$ have been identified for the first time. A total of 120 $\ensuremath{\gamma}$-ray transitions were placed in a level scheme containing 59 levels including two states above the neutron separation energy and a previously unknown $1/{2}^{\ensuremath{-}}$ isomeric state at 127 keV. Spins and parities of several states were deduced and interpreted based on the observed $\ensuremath{\beta}$ feeding and $\ensuremath{\gamma}$-decay pattern.

NATURAL RADIOACTIVITY IN SOME MARBLE SAMPLES

Marbles is an important materials and can be used widely in building construction. When it is considered that human being can spent their most of time in a building, the measurements of 226Ra activity in marble becomes important. Thus some marbles samples have been collected from Mu?la and their natural radioactivity have been measured using a NaI(Tl) gamma-ray spectrometer. Gamma spectrometer was used to determine the activities of uranium (238U), thorium (232Th), potassium (40K). The activity concentrations of 232Th and 238U were obtained by measuring their decay gamma rays. The gamma ray transitions of energies 1760 keV (214Bi), 2610 keV (208Tl) ve 1460 keV (214Bi), were used to determine the concentration of the 238U, 232Th and 40K respectively.

CAESAR—A high-efficiency CsI(Na) scintillator array for in-beam [formula omitted] spectroscopy with fast rare-isotope beams

We report on the construction and commissioning of the high-efficiency CAESium-iodide scintillator ARray CAESAR, a device designed for in-beam γ‐ray spectroscopy experiments utilizing fast beams of rare isotopes at the National Superconducting Cyclotron Laboratory (NSCL) at Michigan State University (MSU). CAESAR consists of 192 CsI(Na) crystals, totaling 290kg of active scintillator material. For 1MeV γ rays, a full-energy-peak efficiency of 35% is achieved at an in-beam energy resolution of better than 10% FWHM after event-by-event Doppler reconstruction of the γ rays emitted by nuclei moving with velocities of v/c∼0.3–0.4. The spectral quality of the array allows for the identification of γ‐ray transitions with intensities of several 10 counts in the full-energy peak and thus opens new avenues for the study of the most exotic nuclei available at the NSCL for in-beam spectroscopy.

Particle- γ spectroscopy of the ( p,d−γ ) Gd155 reaction: Neutron single-quasiparticle states at N=91

A segmented Si telescope and HPGe array is used to study the $^{156}\mathrm{Gd}$($p,d\ensuremath{-}\ensuremath{\gamma}$)$^{155}\mathrm{Gd}$ direct reaction by $d$-$\ensuremath{\gamma}$ and $d$-$\ensuremath{\gamma}$-$\ensuremath{\gamma}$ coincidence measurements using 25-MeV protons. The present investigation is the first time that this $N=91$ nucleus and the $N=90$ region---which is known for a rapid change from vibrational to rotational character, several low-lying ${0}^{+}$ states in the even-even nuclei, and large Coriolis ($\ensuremath{\Delta}\ensuremath{\Omega}=1$) plus $\ensuremath{\Delta}N=2$ mixing in the even-odd nuclei---have been studied by particle-$\ensuremath{\gamma}$ coincidence following a direct reaction with light ions. Gamma-ray energies and branches, excitation energies, angular distributions, and cross sections are measured for states directly populated in the ($p,d$) reaction. A new low-energy doublet state at 592.46 keV (previously associated with the $K=0\ensuremath{\bigotimes}{\frac{3}{2}}^{\ensuremath{-}}[521]$ bandhead) and several new $\ensuremath{\gamma}$-ray transitions (particularly for states with excitation energies $>1$ MeV) are presented. Most notably, the previous $\ensuremath{\nu} {\frac{7}{2}}^{+}[404]$ systematics at and around the $N=90$ transition region are brought into question and reassigned as $\ensuremath{\nu} {\frac{5}{2}}^{+}[402]$. This reassignment makes the $\ensuremath{\nu} {\frac{1}{2}}^{+}[400]$, $\ensuremath{\nu} {\frac{3}{2}}^{+}[402]$, and $\ensuremath{\nu} {\frac{5}{2}}^{+}[402]$ orbitals, which originate from the $3{s}_{1/2}$, $2{d}_{3/2}$, and $2{d}_{5/2}$ spherical states, respectively, responsible for the three largest cross sections to positive-parity states in the ($p,d$)$^{155}\mathrm{Gd}$ direct reaction. These three steeply upsloping orbitals undergo $\ensuremath{\Delta}N=2$ mixing with their $N=6$ orbital partners, which are oppositely sloped with respect to deformation. The presence of these steeply sloped and crossing orbitals near the Fermi surface could weaken the monopole pairing strength and increase the quadrupole pairing strength of neighboring even-even nuclei, which would bring $\ensuremath{\nu} $2p-2h ${0}^{+}$ states below $2\ensuremath{\Delta}$. Indeed, this could account for a large number of the low-lying ${0}^{+}$ states populated in the ($p,t$)$^{154}\mathrm{Gd}$ direct reaction.

High-spin intruder band inIn107

High-spin states in the neutron deficient nucleus $^{107}$In were studied via the $^{58}$Ni($^{52}$Cr, 3p) reaction. In-beam $\gamma$ rays were measured using the JUROGAM detector array. A rotational cascade consisting of ten $\gamma$-ray transitions which decays to the 19/2$^{+}$ level at 2.002 MeV was observed. The band exhibits the features typical for smooth terminating bands which also appear in rotational bands of heavier nuclei in the A$\sim$100 region. The results are compared with Total Routhian Surface and Cranked Nilsson-Strutinsky calculations.

Population of positive-parity states inSc53through one-proton knockout

The one-proton knockout reaction $^{9}\mathrm{Be}(^{54}\mathrm{Ti},^{53}\mathrm{Sc}+\ensuremath{\gamma})X$ at 72 MeV/nucleon has been measured. The location of the first $3/{2}^{\ensuremath{-}}$ state at 2110(3) keV was confirmed, and new $\ensuremath{\gamma}$-ray transitions were observed at 1111(2), 1273(2), 1539(4), and 2495(5) keV. Large spectroscopic strength to excited states in $^{53}\mathrm{Sc}$ was found and attributed to the knockout of $\mathit{sd}$-shell protons.

Rotational alignments inNp235and the possible role ofj15/2neutrons

The role ${j}_{15/2}$ neutron orbitals play in the transuranic region of actinides has been studied by exploring $\ensuremath{\gamma}$-ray transitions between yrast states in $^{235}\mathrm{Np}$, populated utilizing the nucleon-transfer reaction $^{237}\mathrm{Np}$($^{116}\mathrm{Sn}$,$^{118}\mathrm{Sn}$). Two rotational sequences, presumably the two signatures of the ground-state band, have been delineated to high spin for the first time, with the $\ensuremath{\alpha}=+1/2$ and $\ensuremath{\alpha}=\ensuremath{-}1/2$ signature partners reaching $49/{2}^{+}\ensuremath{\hbar}$ (tentatively $53/{2}^{+}\ensuremath{\hbar}$) and $47/{2}^{+}\ensuremath{\hbar}$ (tentatively $51/{2}^{+}\ensuremath{\hbar}$), respectively. Definite isotopic assignments for these in-band transitions were established through $\ensuremath{\gamma}$-ray cross correlations between $^{235}\mathrm{Np}$ and $^{118}\mathrm{Sn}$ and events where at least three $\ensuremath{\gamma}$ rays corresponding to neptunium-like particles were detected. These transitions reveal clear upbends in the aligned angular momentum and kinematic moment of inertia plots; such a phenomenon could indicate a strong interaction between an aligned $\ensuremath{\nu}{j}_{15/2}$ configuration crossing the ground-state band in $^{235}\mathrm{Np}$, which is based on a $\ensuremath{\pi}{i}_{13/2}$ orbital. However, the lack of any signature splitting over the observed frequency range of the $^{235}\mathrm{Np}$ rotational sequences cannot remove the possibility of a $\ensuremath{\pi}{h}_{9/2}$ assignment for the observed band. The role of the $\ensuremath{\nu}{j}_{15/2}$ and $\ensuremath{\pi}{i}_{13/2}$ alignment mechanisms in the deformed U-Pu region is discussed in light of the current spectroscopic data and in the context of the cranked-shell model.

Lifetime effects for high-resolution gamma-ray spectroscopy at relativistic energies and their implications for the RISING spectrometer

The lineshapes and peak position of Doppler corrected γ -ray spectra from in-beam experiments at relativistic energies are investigated with respect to the intrinsic energy resolution of the employed detectors, the particles’ velocities, and the photons’ emission angle uncertainties at the moment of γ -ray emission. The uncertainties in velocity and photon emission angle are dependent on the lifetime of the excited state. The impact of these two observables on the lineshape and energy resolution are studied for the RISING γ -spectrometer by means of simulations and experimental results from a two-step fragmentation experiment at ≈ 200 MeV / u . Potential use of the distinct lineshape for lifetime determination is demonstrated for measured γ -ray transitions.