Search for 22^{22}Na in novae supported by a novel method for measuring femtosecond nuclear lifetimes

Classical novae are thermonuclear explosions in stellar binary systems, and important sources of $^{26}$Al and $^{22}$Na. While gamma rays from the decay of the former radioisotope have been observed throughout the Galaxy, $^{22}$Na remains untraceable. The half-life of $^{22}$Na (2.6 yr) would allow the observation of its 1.275 MeV gamma-ray line from a cosmic source. However, the prediction of such an observation requires good knowledge of the nuclear reactions involved in the production and destruction of this nucleus. The $^{22}$Na($p,\gamma$)$^{23}$Mg reaction remains the only source of large uncertainty about the amount of $^{22}$Na ejected. Its rate is dominated by a single resonance on the short-lived state at 7785.0(7) keV in $^{23}$Mg. In the present work, a combined analysis of particle-particle correlations and velocity-difference profiles is proposed to measure femtosecond nuclear lifetimes. The application of this novel method to the study of the $^{23}$Mg states, combining magnetic and highly-segmented tracking gamma-ray spectrometers, places strong limits on the amount of $^{22}$Na produced in novae, explains its non-observation to date in gamma rays (flux < 2.5x$10^{-4}$ ph/(cm$^2$s)), and constrains its detectability with future space-borne observatories.Comment: 18 pages, 3 figures, 1 tabl

An above-barrier narrow resonance in F-15

Intense and purified radioactive beam of post-accelerated O-14 was used to study the low-lying states in the unbound F-15 nucleus. Exploiting resonant elastic scattering in inverse kinematics with a thick target, the second excited state, a resonance at E-R = 4.757(6)(10) MeV with a width of Gamma = 36(5)(14) keV was measured for the first time with high precision. The structure of this narrow above-barrier state in a nucleus located two neutrons beyond the proton drip line was investigated using the Gamow Shell Model in the coupled channel representation with a C-12 core and three valence protons. It is found that it is an almost pure wave function of two quasi-bound protons in the 2s(1/2) shell. (C) 2016 The Authors. Published by Elsevier B.V

Toward the limit of nuclear binding on the N=Z line : Spectroscopy of Cd 96

A γ-decaying isomeric state (τ1/2=197-17+19 ns) has been identified in Cd96, which is one α particle away from the last known bound N=Z nucleus, Sn100. Comparison of the results with shell-model calculations has allowed a tentative experimental level scheme to be deduced and the isomer to be interpreted as a medium-spin negative-parity spin trap based on the coupling of isoscalar (T=0) and isovector (T=1) neutron-proton pairs. The data also suggest evidence for the population of a 9+ T=1 state, which is predicted by shell-model calculations to be yrast. Such a low-lying T=1 state, which is unknown in lighter mass even-even self-conjugate nuclei, can also be interpreted in terms of the coupling of T=0 and T=1 neutron-proton pairs

Narrow resonances in the continuum of the unbound nucleus 15^{15}F

The structure of the unbound $^{15}$F nucleus is investigated using the inverse kinematics resonant scattering of a radioactive $^{14}$O beam impinging on a CH$_2$ target. The analysis of $^{1}$H($^{14}$O,p)$^{14}$O and $^{1}$H($^{14}$O,2p)$^{13}$N reactions allowed the confirmation of the previously observed narrow $1/2^{-}$ resonance, near the two-proton decay threshold, and the identification of two new narrow 5/2$^{-}$ and 3/2$^{-}$ resonances. The newly observed levels decay by 1p emission to the ground of $^{14}$O, and by sequential 2p emission to the ground state (g.s.) of $^{13}$N via the $1^-$ resonance of $^{14}$O. Gamow shell model (GSM) analysis of the experimental data suggests that the wave functions of the 5/2$^{-}$ and 3/2$^{-}$ resonances may be collectivized by the continuum coupling to nearby 2p- and 1p- decay channels. The observed excitation function $^{1}$H($^{14}$O,p)$^{14}$O and resonance spectrum in $^{15}$F are well reproduced in the unified framework of the GSM

Ground surface deformation of the urban area in complex engineering-geological conditions in the sinking town of Tuzla (Bosnia and Herzegovina)

deformation of the ground surface and buildings in the town of Tuzla. The southern edge of the deposit dips beneath the northern part of the town. Although relatively small size, the deposit represents an extremely complex geological body The slow, natural processes of dissolution of the deposit's eastern part were accelerated by industrial exploitation of saline water (brine) that lasted over 100 years. Exploitation of the western part of the deposit started much later in 1967, by classical dry underground mining. Natural processes and applied exploitation works endangered part of the town above the deposit. Subsidence has reached its peak in 70-s of the last century, when the city lost huge number of its residential, commercial and cultural facilities. Although the salt exploitation ended (2004 and 2007) very complex processes of degradation of wider deposit environment and urban areas are still ongoing, with visible consequences on the ground surface. Featured are the geodynamic phenomena and deformation caused by a complex structural-tectonic structure of the terrain. Analyzed were also geodetic monitoring data for the period 1956-2010 which present important information about the processes of ground surface movements. Deformation on the ground surface is being developed under the influence of various factors. In the part of the town that was investigated and presented in this paper, the consequences of the salt deposit exploitation on the ground surface are predisposed by complex terrain structure

Horizontal movements of the ground surface in the zone of influence of salt exploitation in Tuzla (Bosna and Herzegovina)

This paper focuses on surface movements determined by geodetic methods and occurred as consequence of brine extraction from Tuzla salt deposit (Bosnia and Herzegovina). Previous studies were mainly focalized on vertical movements, but important information about behavior of the deposit is also available from horizontal movement data. In the case of Tuzla salt deposit the geometry and spatial location of leached/empty spaces are unknown and the comparative analysis of vertical and horizontal movement could be really significant. The spatial identification of points with high values of vertical and horizontal movements depends on the geometry of empty spaces. Horizontal movements investigation has been carried out analyzing data collected by several geodetic measurements. The results obtained by the correlated spatial analysis of vertical and horizontal movements, can identify basic geometric characteristics of the leached/empty spaces. The discussed temporal intervals are two characteristic periods, referred to the capacity of the deposit exploitation. Movement rates per year and correlation between horizontal and vertical movements are considered as indicator parameters defining the character of ground deformation. Spatial analysis of these coefficients values has identified high risk areas, and gives additional information in the geological structures definition

Soil gas mapping in the vicinity of Nikola Tesla thermo power plant disposal field

This paper presents the results of identification of natural ionizing irradiation in the vicinity of Nikola Tesla B power plant ash disposal field. The investigations have comprised the determination of natural gas (radon and thoron) activities with a passive discriminative nuclear track detector (CR 39) in the air column of the depth of 80 cm in the soil. The determination of gamma dose rate has been given as well, including the corresponding GPS coordinates of 28 measuring points

Radon survey in the high natural radiation region of Niska Banja, Serbia

A radon survey has been carried out around the town of Niska Banja (Serbia) in a region partly located over travertine formations, showing an enhanced level of natural radioactivity. Outdoor and indoor radon concentrations were measured seasonally over the whole year, using CR-39 diffusion type radon detectors. Outdoor measurements were performed at 56 points distributed over both travertine and alluvium sediment formations. Indoor radon concentrations were measured in 102 living rooms and bedrooms of 65 family houses. In about 50% of all measurement sites, radon concentration was measured over each season separately, making it possible to estimate seasonal variations, which were then used to correct values measured over different periods, and to estimate annual values. The average annual indoor radon concentration was estimated at over 1500 Bq/m(3) and at about 650 Bq/m(3) in parts of Niska Banja located over travertine and alluvium sediment formations, respectively, with maximum values exceeding 6000 Bq/m(3). The aver age value of outdoor annual radon concentration was 57 Bq/m(3), with a maximum value of 168 Bq/m(3). The high values of indoor and outdoor radon concentrations found at Niska Banja make this region a high natural background radiation area. Statistical analysis of our data confirms that the level of indoor radon concentration depends primarily on the underlying soil and building characteristics. (c) 2006 Elsevier Ltd. All rights reserved