Large Volume Ge Research Articles

Model independent Jπ assignments in 38Ar from γ-ray experiments in heavy-ion induced reactions

High-spin states of 38Ar and 35Cl have been investigated with the 24Mg( 16O, 2pγ) 38Ar and 24Mg( 16O, pαγ) 35Cl reactions at beam energies of 38 and 45 MeV. The experiments consisted of γ-γ coincidence, angular distribution and linear polarization measurements. A high-resolution large volume Ge(Li)-NaI(Tl) Compton-suppression spectrometer and a three-Ge(Li) Compton polarimeter were used. The analysis of the data, without assumptions about the reaction mechanism for the formation of the levels under study, is discussed. Unambiguous spin-parity assignments of J π = 6 +, 8 +, and limitations of (5, 6, 7) and (7, 8 +, 9) for the 38Ar levels at E x = 6408.3±0.2, 7609.3±0.3, 8012.9±0.3 and 10173.8±0.4 keV, respectively, are obtained. They are compared with results of shell-model calculations. Mixing ratios and spin-alignment attenuation factors for several transitions and levels in 38Ar and 35Cl are reported.

Decays ofBa126andCs126

The neutron deficient $^{126}\mathrm{Ba}$ has been produced by the reactions $^{115}\mathrm{In}(^{16}\mathrm{O},5n)^{126}\mathrm{La}\stackrel{\ensuremath{\beta}+,\mathrm{E}\mathrm{C}}{\ensuremath{\rightarrow}}^{126}\mathrm{Ba}$, $^{121}\mathrm{Sb}(^{11}\mathrm{B},6n)^{126}\mathrm{Ba}$, and $^{133}\mathrm{Cs}(p,8n)^{126}\mathrm{Ba}$. Its decay properties have been studied in equilibrium with the daughter activity of $^{126}\mathrm{Cs}$. About 100 $\ensuremath{\gamma}$ rays have been observed to be associated with the decay of the $^{126}\mathrm{B}\mathrm{a}\ensuremath{-}$$^{126}\mathrm{Cs}$ mass chain. The assignment of $\ensuremath{\gamma}$ rays to $^{126}\mathrm{Ba}$ and $^{126}\mathrm{Cs}$ activities has been done by measuring $\ensuremath{\gamma}$-ray spectra gated by $K$ x rays of Cs and Xe, respectively. The $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ and $\ensuremath{\beta}\ensuremath{-}\ensuremath{\gamma}$ coincidence studies have been performed by using large volume Ge(Li) and plastic detectors and a two parameter analyzer system. Conversion coefficients of intense $\ensuremath{\gamma}$ transitions have been measured by using a conversion electron spectrometer consisting of a Ge(Li) detector and a cooled Si(Li) detector. Decay schemes of $^{126}\mathrm{Cs}$ and $^{126}\mathrm{Ba}$ are proposed. The levels in $^{126}\mathrm{Xe}$ are compared with predictions of the collective model.RADIOACTIVITY $^{126}\mathrm{Ba}$, $^{126}\mathrm{Cs}$ [from $^{115}\mathrm{In}(^{16}\mathrm{O},5n)$, $^{121}\mathrm{Sb}(^{11}\mathrm{B},6n)$, and $^{133}\mathrm{Cs}(p,8n)$]; measured ${E}_{\ensuremath{\gamma}}$, ${I}_{\ensuremath{\gamma}}$, ${I}_{\mathrm{ce}}$, $\ensuremath{\beta}\ensuremath{-}\ensuremath{\gamma}$, $\mathrm{x}\ensuremath{-}\ensuremath{\gamma}$, $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coincidence; deduced levels, $J$, $\ensuremath{\pi}$, $log\mathrm{ft}$, CC, multipolarities; Ge(Li), Si(Li), plastic detectors; natural targets.

Decays ofKr88andRb88

The $\ensuremath{\gamma}$ rays following the $\ensuremath{\beta}$ decays of $^{88}\mathrm{Kr}$ and $^{88}\mathrm{Rb}$ have been studied, using both large volume Ge(Li) detectors for singles and coincidence measurements and anti-Compton spectrometry for singles measurements. Level schemes for $^{88}\mathrm{Rb}$ and $^{88}\mathrm{Sr}$ were constructed from the data and 74 of 81 $\ensuremath{\gamma}$ rays observed in the decay of $^{88}\mathrm{Kr}$ were placed in the $^{88}\mathrm{Rb}$ level scheme with 23 excited states. For the decay of $^{88}\mathrm{Rb}$, all of the observed 27 $\ensuremath{\gamma}$ rays have been placed in the (well known) level structure of $^{88}\mathrm{Sr}$. Spin and parity assignments have been deduced from $\ensuremath{\beta}$-decay $log\mathrm{ft}$ values and $\ensuremath{\gamma}$-ray transition patterns. Possible shell-model interpretations are presented for the level schemes.RADIOACTIVITY $^{88}\mathrm{Kr}$, $^{88}\mathrm{Rb}$ [from $^{235}\mathrm{U}(n,f)$]; measured ${E}_{\ensuremath{\gamma}}$, ${I}_{\ensuremath{\gamma}}$, $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coin. Ge(Li) detectors, Compton suppression. $^{88}\mathrm{Rb}$, $^{88}\mathrm{Sr}$ deduced levels, $J$, $\ensuremath{\pi}$, $log\mathrm{ft}$. Mass-separated $^{88}\mathrm{Kr}$ activity.

A broad-range on-line electron spectrometer

Special features of a broad-range high-transmission electron spectrometer, incorporating a solenoid and a Si(Li) detector are described. The source-detector distance is 72 cm. A detector vacuum-lock system makes it possible to maintain the Si(Li) diode at liquid-nitrogen temperature during installation and choose an optimum detector position with respect to the magnetic field. A baffle to separate electrons from positions is described. A brief presentation is given of a cleaning procedure for Si(Li) diodes. An absolute efficiency of 11% of 4π for 481 keV electrons is measured employing a 3 mm thick, 110 mm 2 detector. The resolution is 1.3 keV and 2.0 keV fwhm at 92 keV and 975 keV electron energies, respectively. The time spectrum between conversion electrons measured in the solenoid and γ-rays measured with a large-volume Ge(Li) detector shows a slope of a few nanoseconds.

Detection of prompt deexcitation γ-rays following bremsstrahlung-induced reactions with the aid of large volume Ge(Li) detectors

An experimental arrangement at the bremsstrahlung beam of a 65 MeV electron linac has been optimized with regard to the detection of prompt deexcitation γ-rays from small target quantities by Ge(Li) detectors. The 100 cm 3 Ge(Li) diodes have been calibrated by means of radioactive sources and radiative proton capture reactions. The influence of counting rate effects and background radiation during the bremsstrahlung burst are discussed. Deexcitation photon spectra from 28Si(γ,γ′), 25Mg(γ,χγ′) and 31P(γ,χγ′) reactions are presented.

Level structure ofPd106from the decay ofRhg106

The low-spin level structure of $^{106}\mathrm{Pd}$ was studied using high-resolution large volume Ge(Li) detectors for $\ensuremath{\gamma}$-ray singles, coincidence, and angular correlation measurements. The measurements allowed the resolution of most of the discrepancies found among previous studies. In particular, the use of two Ge(Li) detectors for coincidences and angular correlations allowed unambiguous placement of previously multiply placed $\ensuremath{\gamma}$ rays and resolved discrepancies in energy level or ${J}^{\ensuremath{\pi}}$ assignments. The experimental level structure and $B(E2)$ ratios are compared with predictions of an anharmonic spherical vibrator model and a rotor-vibrator model; we find that the evidence strongly supports the latter of the two models.

Decay of68Cum(3.75 min) and68Cug(30s)

The decay of the 68Cum+g has been investigated using a large volume Ge(Li) spectrometer. The 68Cu activities were produced by irradiating enriched 68Zn as well as spectroscopically pure Zn targets with fast neutrons. The isomer is seen to decay 91% via the isomeric transitions to 68Cug. The spin-parity of 68Cug has been established to be 1+and the excited levels in 68Cu have been interpreted as 2+ (84.6 keV), 3- (610.5 keV) and 6-721.5 keV). The results are incorporated into a revised decay scheme of 68Cum+g.

Allowed electron-capture branches in the decay of 34mCl

The decay of 34mCl has been studied with 36 and 100 cm 3 Ge(Li) detectors and with a high-resolution large volume Ge(Li)-NaI(Tl) Compton-suppression spectrometer. The 34mCl activity was produced with the reaction 24Mg( 12C, pn) 34Cl at E( 12 C) = 35 MeV by bombarding thick natural Mg targets. The half-life was measured to be τ 1 2 = 32.06 ± 0.08 min . Nine γ-ray transitions were observed including four γ-rays not seen previously. The measured γ-ray intensities determine new electron-capture branches of (0.030 ± 0.006) % and (0.032 ± 0.003) % to 34S levels at 4.69 and 4.88 MeV with log ft values of 5.48 ± 0.08 and 5.26 ±0.04, respectively. These log ft values imply allowed transitions and are consistent with the known J π values of J π = 4 + and 3 + of the 4.69 and 4.88 MeV levels, respectively. A lower limit of log ft ⪢ 6.9 is obtained for the allowed electron-capture branch to the J π = 2 +, 4.89 MeV level. Other previously observed decay branches have been confirmed. Since the decay of 34mCl proceeds (46.9 ± 1.0)% to the 34Cl ground state, the latter decay was studied concurrently; 34Cl(0)with J π = 0 +, T = 1 decays exclusively to its analog 34S(0) and the sum of the intensities of four other allowed branches is less than 1.2 × 10 −4 of the intensity of the ground-state branch. The experimental results are compared with recent shell-model calculations performed in a large configuration space.

The decays of 21.55 min 162gTm and 24.3 s 162Tm (a new isomer)

The decay of the 21.55 min ground state and of the 24.3 s isomeric state of 162Tm was investigated with semiconductor detectors. The γ-ray spectrum was investigated with a Compton-suppression Ge(Li)-NaI(Tl) arrangement. A Si (Li) detector, mounted in an electron transport solenoid, was used to investigate the conversion electron spectrum. Three-dimensional coincidence measurements were performed with large-volume Ge(Li) detectors. The 162Tm ground state has spin-parity 1 − and Nilsson assignment p[411]↓− n[521]↑. An allowed β-transition (log ft ≈ 6.4) was observed to a 2 −, 2 octupole vibrational level at 1572.84 keV. The Q-value determined from positon-gamma coincidence measurements is 4705 ± 70 keV. The discrepancy of the experimental K / β + ratio with theoretical predictions might possibly be explained by a large number of unobserved weak γ-rays besides the total of 315 stronger ones observed in this study. The average β-strength function was calculated to be 1.2 × 10 −5. Among the 50 levels observed in the decay, the 2 +, 4 + and 6 + members of the ground-state band, the 2 +, 3 + and 4 + members of the γ-band, several 0 + and 2 + members of the K = 0 β-bands and 1 −, 2 − and 3 − octupole vibrational levels were identified. Parameter values Z γ (0) and Z γ (2) determining the mixing between the γ-band and the ground-state band, allow no conclusive evidence about unequalness of the intrinsic quadrupole moments of the ground states and the γ-band. The Z(0) parameters, determining the mixing between the β-bands and the ground-state band, and X parameters determining the ratio of E0 to E2 transition probabilities, were deduced. A previously unreported 24.3 sec isomer in 162Tm was observed to decay in 10% of the cases by an allowed unhindered (log ft = 4.7) β-ray transition to a level at 1712.20 keV in 162Er. The Nilsson configurations assigned to the isomeric and 1712.20 keV levels are p[523]↑ + n[521]↑ 5+ and n[523]↓ + n[521]↑ 4+ respectively. The isomeric level decays in 90% of the cases by an E3 transition ( E IT < 125 keV) to a p[404]↓ −n[521]↑ 2− level at 66.90 keV in 162Tm, which decays by an (M1+ < 40 % E2) to the 21.55 min 162Tm 1 − ground state.

Properties ofGd156levels populated in the decay of 15.2 dayEu156

$\ensuremath{\gamma}$ rays emitted in the radioactive decay of 15.2 day $^{156}\mathrm{Eu}$ have been studied with large volume Ge(Li) detectors in both singles and coincidence modes. A total of 95 $\ensuremath{\gamma}$-ray transitions were observed in the $^{156}\mathrm{Eu}$ decay and 84 of these are placed in the $^{156}\mathrm{Gd}$ level scheme which consists of 26 excited states. Seven of these levels are assigned here for the first time. Many of the inconsistencies that have complicated the interpretation of previous work have been resolved in these studies. In particular, it has been possible in the extensive coincidence measurements to resolve several multiplets in the $\ensuremath{\gamma}$-ray spectrum and, therefore, to obtain accurate branching intensities for members of both the $\ensuremath{\gamma}$-vibrational band and two ${K}^{\ensuremath{\pi}}={0}^{+}$ excited bands.RADIOACTIVITY $^{156}\mathrm{Eu}$ (from $n$ capture on $^{154}\mathrm{Sm}$); measured ${E}_{\ensuremath{\gamma}}$, ${I}_{\ensuremath{\gamma}}$, $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coin; deduced $log\mathrm{ft}$. $^{156}\mathrm{Gd}$ deduced levels, $J$, $\ensuremath{\pi}$, ICC. Enriched $^{154}\mathrm{Sm}$ target, Ge(Li) detectors.

Instrumental method for the determination of trace elements in water samples by neutron activation analysis

Thermal neutron activation analysis and a large-volume high-resolution Ge(Li) gammaray spectrometer, connected on-line to a DEC PDP 8/L computer, have been used to measure the concentrations of Na, Sc, Cr, Fe, Co, Ni, Zn, As, Se, Br, Rb, Ag, Sb, Cs, W and Hg in some Italian subsurface water samples. The instrumental method requires neither a chemical separation technique nor a pre- or post-concentration of the trace elements to be detected. As a consequence, this method eliminates many inherent errors associated with chemical determinations. The technique is sensitive, precise and particularly suitable for routine analysis of many trace elements at both natural and pollution levels in water samples. The interferences due to fast neutron (n, p) and (n, α) reactions are not appreciable, with the only exception of the54Fe(n, p)54Mn and58Ni(n, p)58Co reactions. Losses of volatile, elements, e. g. As, Br and Hg, during irradiation proved to be negligible.

A Satellite-Borne High Resolution Ge(Li) Gamia-Ray Spectrometer System Part 2: Description of the Electronic, Data Handling and Auxiliary Sensor Systems

The first high-resolution gamma-ray spectrometer system employing Ge(Li) detectors has been designed and successfully flown on an earth-orbiting satellite. The complete scientific payload consists of two large-volume Ge(Li) spectrometers for the measurements of photons in the 40 keV - 2.8 MeV energy range with 4096-channel energy resolution and six auxiliary sensors for measuring the location, intensity and energy spectra of charged-particle backgrounds in earth orbit. To achieve and maintain an overall systems resolution of 3.5-4 keV in photon energy, a low-noise bias power supply and charge sensitive preamplifier-amplifier combination were designed for the germanium detectors. Amplified signals are analyzed in a 4096-channel analyzer of the linear-ramp type, with an integral and differential linearity of ± 0.2 percent and ± 1.0 percent, respectively. Individual pulse-height addresses are sampled at a rate of 1625 addresses/sec and time tagged together with absolute count-rate data by the experiment digital-data-handling system and then stored on magnetic tape recorders. A detailed description of the gamma-ray spectrometer electronic system including the method of collecting and analysis of flight data is given.

Double-photon decay in 90Zr nucleus

Double-photon decay in the 0 + to 0 + transition in 90Zr was measured with two large-volume Ge(Li) detectors, at angles of 90° and 180°. The branching ratio of double-photon decay with respect to the sum of internal-conversion electrons and internal pairs was (3.17 ± 0.77) × 10 −4. The angular correlation of two photons is in agreement with that of (E1, E1) transition, although it does not exclude other possibilities.

Search for weak transitions in the decay of125Sb and accurate gamma intensities

The weak transitions in the decay of125Sb have been investigated through gamma ray measurements with high resolution X-ray and with large volume Ge(Li) detectors. The 172.6, 178.8 and 198.5 keV gamma rays are confirmed, while others previously reported were not. Accurate intensities were obtained for the stronger transitions. The weighted averages of these intensities which cover the range of 116 to 670 keV are useful for calibration of Ge(Li) systems.

States in Odd-OddCu62Populated by the Decay ofZn62

The decay of 9.2-h $^{62}\mathrm{Zn}$ to states in odd-odd $^{62}\mathrm{Cu}$ has been studied with the aid of large-volume Ge(Li) $\ensuremath{\gamma}$-ray detectors. 19 $\ensuremath{\gamma}$ rays were found to belong to this decay, and all were placed in a decay scheme containing states in $^{62}\mathrm{Cu}$ at 0 (${J}^{\ensuremath{\pi}}={1}^{+}$), 40.94 (${2}^{+}$), 243.44 (${2}^{+}$), 287.98 (${2}^{+}$), 426.3 (${3}^{+}$), 548.4 (${1}^{+}$), 637.5 (${1}^{+}$), 915.6 (${[1]}^{+}$), 1142.5 (${[0,\phantom{\rule{0ex}{0ex}}1]}^{+}$), 1280.8 (${[0,\phantom{\rule{0ex}{0ex}}1]}^{+}$), and 1429.9 keV (${[1,\phantom{\rule{0ex}{0ex}}0]}^{+}$). These were combined with existing in-beam $\ensuremath{\gamma}$-ray particle-transfer data to yield a rather complete $^{62}\mathrm{Cu}$ level scheme. The status of shell-model calculations in this nuclear region is discussed, and it is demonstrated that a gratifying number of facts about the low-lying $^{62}\mathrm{Cu}$ states can be explained using simple odd-odd configurations as predicted by the neighboring odd-mass nuclei.

Levels in 89Rb Populated by the Beta Decay of 89Kr

The decay of 3.2 min 89Kr has been investigated with small and large volume Ge(Li) detectors used singly and in a dual parameter coincidence arrangement. A total of 162 gamma rays are identified with the decay of this isotope, 120 of which are placed in a level scheme on the basis of gamma–gamma coincidence evidence and the energy differences between established levels. Levels at 220.9, 497.7, 577.3, 586.1, 930.7, 931.5, 997.6, 1195.5, 1324.6, 1530.1, 1533.6, 1694.1, 1822.1, 1998.9, 2160.5, 2401.5, 2598.5, 2867.2, 3099.7, 3329.9, 3363.1, 3372.1, 3534.1, 3719.3, 4145.1, 4217.4, 4340.9, and 4487.5 keV are well established by coincidence data and many energy sums. The levels proposed at 2783.4, 3429.7, 3456.6, 3978.4, 4058.4, and 4406.5 keV are less securely established. The most probable spins of the ground state and the first two excited states arc 3/2−. 5/2− and 1/2− respectively. Improved energies and intensities of the gamma rays from the decay of 15 min 89Rb have also been determined.

Decay ofP35

The $\ensuremath{\beta}$ decay of $^{35}\mathrm{P}$ to levels of $^{35}\mathrm{S}$ has been studied with a large-volume Ge(Li) detector and a gas-flow proportional counter. The $^{35}\mathrm{P}$ was produced via the $^{37}\mathrm{Cl}(t,\ensuremath{\alpha}p)^{35}\mathrm{P}$ reaction by bombardment of NaCl and LiCl targets with 16-MeV tritons, and was chemically separated by conversion to phosphate ion and adsorption on a selective polyvalent anion exchanger. The half-life was measured to be 47.4 \ifmmode\pm\else\textpm\fi{} 0.8 sec. Only one $\ensuremath{\gamma}$ transition was observed, at 1572.2 \ifmmode\pm\else\textpm\fi{} 0.4 keV. The $^{35}\mathrm{P}$ decays ${99}_{\ensuremath{-}7}^{+10}$% ($logft=4.1\ifmmode\pm\else\textpm\fi{}0.1$) to the 1572-keV ${\frac{1}{2}}^{+}$ first excited level of $^{35}\mathrm{S}$ and 9% ($log\mathrm{ft}6.1$) to the ${\frac{3}{2}}^{+}$ ground state, whence its spin-parity is deduced to be ${\frac{1}{2}}^{+}$. Less than 0.45% of the $\ensuremath{\beta}$ transitions proceed to any of the other known $^{35}\mathrm{S}$ levels. The results are compared with the predictions of a recent shell-model treatment.

An Anticoincidence Guarded, Ge(Li) Detector for Environmental Level Gamma Energy Analyses

The environmental level gamma energy system developed at Atlantic Richfield Hanford Company laboratories consists of a single, large volume Ge(Li) detector with an NaI(Tl) anticoincidence guard, all operating in a laminar flow "Clean Room." A peak height to Compton edge ratio of better than 250:1, together with a reducing background, enables analysis of sample volumes from point sources to 700 cc.

Monthly deposition of 137Cs in the period from 1964 through 1971 at Osaka, Japan.

Monthly deposition of 137Cs at Osaka was measured in the period of 7 years from July 1964 through July 1971. Gamma-ray spectra of the samples collected monthly by the basin method were measured with a large volume Ge(Li) detector shielded with 20 cm iron in order to determine their 137Cs activities. On close examination of the variation of monthly 137Cs deposition, it is noted that, besides the seasonal variation of so-called “spring maximum”, there appeared many peaks, each of which can be assumed to have been caused by the influence of a nuclear explosion. Yearly 137Cs depositions during the period were also estimated and compared with those measured by another institute.

Internal Conversion and Gamma-Ray Studies of the Decay of 101Pd

The decay of 8.47 h 101Pd has been studied by use of large volume Ge(Li)-detectors and a high resolution 50 cm radius double-focussing beta-ray spectrometer. By combining measured internal conversion and gamma-ray intensities multipolarities for all prominent transitions were deduced from the conversion coefficients. Based on the assigned multipolarities a consistent level scheme of 101Rh has been constructed where spin-parity assignments are given for all but one level.