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We present a detailed map of uranium distribution and its uncertainties in the Variscan Basement of Northeastern Sardinia (VBNS) at a scale of 1:100,000. An area of 2100 km2was investigated by means of 535 data points obtained from laboratory andin situgamma-ray spectrometry measurements. These data volume corresponds to the highest sampling density of the European Variscides, aimed at studying the genetic processes of the upper crust potentially triggered by an enrichment of radiogenic heat-producing elements. For the first time, the Kriging with Variance of Measurement Error method was used to assign weights to the input data which are based on the degree of confidence associated with the measurements obtained using different gamma-ray spectrometry techniques. A detailed tuning of the model parameters for the adopted Experimental Semi-Variogram led to the identification of a maximum distance of spatial variability coherent to the observed tendency of the experimental data. We demonstrate that the obtained uranium distribution in the VBNS, characterized by several calc-alkaline plutons emplaced within migmatitic massifs and amphibolite-facies metamorphic rocks, is an excellent benchmark for the study of ‘hot’ collisional chains. The uranium map of VBNS, and in particular the Arzachena minor pluton, confirms the emplacement model based on the recognition of the different petrological associations characterizing the Variscan magmatic processes in the Late Paleozoic. Furthermore, the presented model of the uranium content of the geological bedrock is a potential baseline for future mapping of radon-prone areas. [ABSTRACT FROM PUBLISHER]

High-spin states in 138Nd were investigated using the reaction 94Zr(48Ca, 4n), detecting coincident γ rays with the GASP spectrometer. A rich level scheme was constructed including four bands of negative parity at low spins, eight bands of dipole transitions, and eight bands of quadrupole transitions at medium spins. The cranked shell model and the tilted-axis cranking model are used to assign configurations to the observed bands, where zero pairing is assumed. For selected configurations the case of finite pairing is also considered. A consistent notation for configuration assignment that applies for both zero and finite pairing is introduced. The observed bands are interpreted as rotation around the short and long principal axes (quadrupole bands), as well as around a tilted axis (dipole bands). The dipole bands have an intermediate character, between magnetic and collective electric rotation. A pair of dipole bands is identified as candidates for chiral partners. The possible existence of the wobbling mode at low deformation and medium spins is discussed. The consistent interpretation of the multitude of observed bands strongly supports the existence of stable triaxial deformation at medium spins in 138Nd. [ABSTRACT FROM AUTHOR]

The level scheme of the neutron-deficient nucleus 95Pd has been studied with the 58Ni + 40Ca fusionevaporation reaction at 135 MeV with the GASP y-ray array, the ISIS silicon ball, and the N-ring neutron detector. Excited levels with spins at least up 45/2 h are reported for both parities. The observed experimental data are compared to large-scale shell-model calculations. [ABSTRACT FROM AUTHOR]

Abstract: An increasing demand of environmental radioactivity monitoring comes both from the scientific community and from the society. This requires accurate, reliable and fast response preferably from portable radiation detectors. Thanks to recent improvements in the technology, γ spectroscopy with sodium iodide scintillators has been proved to be an excellent tool for in-situ measurements for the identification and quantitative determination of γ ray emitting radioisotopes, reducing time and costs. Both for geological and civil purposes not only 40K, 238U, and 232Th have to be measured, but there is also a growing interest to determine the abundances of anthropic elements, like 137Cs and 131I, which are used to monitor the effect of nuclear accidents or other human activities. The Full Spectrum Analysis (FSA) approach has been chosen to analyze the γ spectra. The Non Negative Least Square (NNLS) and the energy calibration adjustment have been implemented in this method for the first time in order to correct the intrinsic problem related with the χ 2 minimization which could lead to artifacts and non physical results in the analysis. A new calibration procedure has been developed for the FSA method by using in situ γ spectra instead of calibration pad spectra. Finally, the new method has been validated by acquiring γ spectra with a 10.16cm×10.16cm sodium iodide detector in 80 different sites in the Ombrone basin, in Tuscany. The results from the FSA method have been compared with the laboratory measurements by using HPGe detectors on soil samples collected particular, the 137Cs isotopes has been implemented in the analysis since it has been found not negligible during the in-situ measurements. [Copyright &y& Elsevier]

The spectroscopic quadrupole moment of the T1/2=9.4(5) ns isomer in 193Pb at an excitation energy Eex=(2585+x) keV is measured by the time-differential perturbed angular distribution method as ∣Qx∣=2.6(3) e b. Spin and parity Iπ=27/2¯ are assigned to it based on angular distribution measurements. This state is the band head of a magnetic-rotational band, described by the 1i13/2 subshell with the (3s1/2-21h9/21i13/2)11- proton excitation. The pairing-plus-quadrupole tilted-axis cranking calculations reproduce the measured quadrupole moment with a moderate oblate deformation ϵ2=-0.11, similar to that of the 11¯proton intruder states, which nuclei in the region. This is the first direct measurement of a quadrupole moment and thus of the deformation of a magnetic-rotational band head. [ABSTRACT FROM AUTHOR]

High-spin states in the odd-proton nucleus 173Lu have been populated in a 170Er(7Li,4n) reaction and the emitted γ-radiation was detected with the GASP array. The favoured and unfavoured sequences of the π1/2- [541] band have been considerably extended. The favoured sequence does not show any indication of a band crossing up to a rotational frequency of ≈ 0.45 MeV. This is the largest crossing frequency ever observed for 1/2- [541] bands of odd-proton nuclei with 67 < Z < 77 and 90 < N < 106. Previous Cranked Shell Model (CSM) calculations underestimate the crossing frequency by 100 keV. [ABSTRACT FROM AUTHOR]

High-spin states in the odd-odd nucleus 172Lu have been populated in a 170Er(7Li, 5n) reaction and the emitted γ-radiation was detected with the GASP array. Two sequences of a new identical band have been observed with the transition energies in the favoured and unfavoured sequences being identical within &ssymp; 3 keV at low spins and &ssymp;1 keV at high spins over the whole observed spin range. An interpretation as a pseudo-spin singlet band of π1/2 -[541] ® v1/2 [4201 configuration is proposed. It represents the best example of a pseudo-spin singlet band in normal deformed nuclei known until now. [ABSTRACT FROM AUTHOR]

The reactions [sup 16]O([sup 7]Li, 2n) and [sup 16]O([sup 7]Li, np) populating [sup 21]Na and [sup 21]Ne have been studied at E[sub L]=27 MeV using the GASP γ-detector array. The level schemes for [sup 21]Na and [sup 21]Ne have been extended to higher spin. The population of the bands with K=3/2 and 1/2, forming parity doublets, are compared. Preferential E1 decay between bands of opposite parity is observed in agreement with the octupole scenario. The structure of these bands can be interpreted as consisting of an instrinsic asymmetric ([sup 4]He+[sup 16]O) structure with octupole deformation.© 2003 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

The high-spin states of 80Y have been studied with the reactions 24Mg(58Ni, pnγ) at 180 MeV and 58Ni(24Mg, pnγ) at 77 MeV. Gamma-ray transitions in this nucleus have been unambiguously assigned by using the GASP detector array in conjunction with the recoil mass spectrometer CAMEL and the ISIS Silicon detector ball. These transitions have been arranged into several rotational bands extending up to an excitation energy of about 12 MeV and spin 24 ℏ. The bands are discussed within the framework of the interacting boson–fermion–fermion and cranked shell models. [Copyright &y& Elsevier]

High-efficiency arrays for γ spectroscopy, now available in several Laboratories, make possible the measurement of very weak cross-over transitions of high potential interest. A limit to the measurement possibilities comes, however, from the simultaneous detection of two γ-rays of a stop-over cascade (or “sum-up”), which cannot be distinguished from the true detection of the cross-over transition. We propose a new method to measure (and correct for) the sum-up effect, which can be used with symmetric γ detector arrays (like GASP and GAMMASPHERE), and discuss the possible techniques for identifying and estimating quantitatively the contribution of random pile-up, which can be sizeable at high counting rate. These ideas have been experimented at GASP in a dedicated measurement with a radioactive source of 52Mn. The results of this measurement are presented and discussed. Moreover, as a significant example, the method is applied to deduce the intensity of the E3 cross-over transition from the lowest 3− state of 148Gd. [Copyright &y& Elsevier]