Natural and artificial radioactive pollution in sediment and soil samples of the Bosphorus, Istanbul

This study focused on the determination of natural (²³⁸U, ²³²Th, and ⁴⁰K) and artificial (¹³⁷Cs) radionuclide concentrations both in 55 sediment samples collected from various depths in the Bosphorus and 5 soil samples from the coastline of the Bosphorus, Istanbul, using gamma-ray spectrometry with an HPGe detector. The mean activity concentrations of natural ²³⁸U, ²³²Th, and ⁴⁰K and anthropogenic ¹³⁷Cs were determined to be 11.41 ± 0.21 Bq kg^-1, 6.87 ± 0.16 Bq kg^-1, 369.61 ± 3.41 Bq kg^-1, and 6.54 ± 0.11 Bq kg^-1, respectively, in the sediment samples. The average activity concentrations of ²³⁸U, ²³²Th, ⁴⁰K, and ¹³⁷Cs radionuclides in the soil samples were also measured to be 11.65 ± 0.18 Bq kg^-1, 9.55 ± 0.15 Bq kg^-1, 369.43 ± 3.09 Bq kg^-1, and 4.57 ± 0.09 Bq kg^-1, respectively. Radiological contour maps based on the activity concentrations of natural and artificial radionuclides in the sediment samples for the Bosphorus, Istanbul, were created. The total annual effective doses due to soil samples were calculated to be 34.58 μSv y^-1.

Radiation doses due to smoking different types of tobacco leaves grown in Turkey

The activity concentrations of ²³⁸U, ²³²Th, ⁴⁰ K and ¹³⁷Cs radionuclides in 25 samples of tobacco leaves grown in Turkey have been measured using a high purity co-axial germanium detector. The measured activity concentrations for ²³⁸U ranged from 3.6 to 22.5 Bq kg^-1 with an average of 9.8 Bq kg^-1, for ²³²Th from 0.8 to 11.0 Bq kg^-1 with an average of 2.4 Bq kg^-1, and for ⁴⁰ K from 360.3 to 1,479.5 Bq kg^-1 with an average of 810.0 Bq kg^-1. The concentrations of ¹³⁷Cs, the residue of fallout from the Chernobyl reactor accident, were found to range from 0.2 to 2.1 Bq kg^-1 with an average of 0.5 Bq kg^-1. The results indicate that the average activity concentrations of ²³⁸U and ²³²Th lie within the range of measured values worldwide, whereas for ⁴⁰ K the average was found to be higher. The average annual effective radiation doses from the inhalation of the corresponding tobacco smoke by an adult smoking 20 cigarettes per day was deduced to be 93.3 μSv y^-1 for ²³⁸U, 193.2 μSv y^-1 for ²³²Th, 5.6 μSv y^-1 for ⁴⁰ K, and 292.1 μSv y^-1 in total. The average annual effective dose from ¹³⁷Cs was calculated to be 8.5 nSv y^-1. The resulting average annual effective radiation doses of 0.3 mSv due to the inhalation of natural radiation sources in tobacco were compared with studies worldwide and found much smaller than the worldwide average effective dose of 1.26 mSv. It is concluded that smoking may contribute a non-negligible fraction to the annual effective dose depending on cigarette consumption and activity concentration in tobacco. This study is the first in which natural and anthropogenic radioactivity in tobacco in Turkey was measured. Therefore, it is considered as a baseline study. Further studies are needed to investigate the role of tobacco refinement in the observed reduction of ²³⁸U concentration of refined tobacco.

Large Impact of the Decay of Niobium Isomers on the Reactor ν[over ¯]_{e} Summation Calculations

Even mass neutron-rich niobium isotopes are among the principal contributors to the reactor antineutrino energy spectrum. They are also among the most challenging to measure due to the refractory nature of niobium, and because they exhibit isomeric states lying very close in energy. The β-intensity distributions of ^{100gs,100m}Nb and ^{102gs,102m}Nb β decays have been determined using the total absorption γ-ray spectroscopy technique. The measurements were performed at the upgraded Ion Guide Isotope Separator On-Line facility at the University of Jyväskylä. Here, the double Penning trap system JYFLTRAP was employed to disentangle the β decay of the isomeric states. The new data obtained in this challenging measurement have a large impact in antineutrino summation calculations. For the first time the discrepancy between the summation model and the reactor antineutrino measurements in the region of the shape distortion has been reduced.

Hindered Gamow-Teller decay to the odd-odd N=Z (62)Ga: absence of proton-neutron T=0 condensate in A=62

Search for a new kind of superfluidity built on collective proton-neutron pairs with aligned spin is performed studying the Gamow-Teller decay of the T=1, J(π)=0+ ground state of (62)Ge into excited states of the odd-odd N=Z nucleus (62)Ga. The experiment is performed at GSI Helmholtzzentrum für Shwerionenforshung with the (62)Ge ions selected by the fragment separator and implanted in a stack of Si-strip detectors, surrounded by the RISING Ge array. A half-life of T1/2=82.9(14)  ms is measured for the (62)Ge ground state. Six excited states of (62)Ga, populated below 2.5 MeV through Gamow-Teller transitions, are identified. Individual Gamow-Teller transition strengths agree well with theoretical predictions of the interacting shell model and the quasiparticle random phase approximation. The absence of any sizable low-lying Gamow-Teller strength in the reported beta-decay experiment supports the hypothesis of a negligible role of coherent T=0 proton-neutron correlations in (62)Ga.

Observation of the β-delayed γ-proton decay of (56)Zn and its impact on the Gamow-Teller strength evaluation

We report the observation of a very exotic decay mode at the proton drip line, the β-delayed γ-proton decay, clearly seen in the β decay of the T_{z}=-2 nucleus ^{56}Zn. Three γ-proton sequences have been observed after the β decay. Here this decay mode, already observed in the sd shell, is seen for the first time in the fp shell. Both γ and proton decays have been taken into account in the estimation of the Fermi and Gamow-Teller strengths. Evidence for fragmentation of the Fermi strength due to strong isospin mixing is found.

Observation of low- and high-energy Gamow-Teller phonon excitations in nuclei

Gamow-Teller (GT) transitions in atomic nuclei are sensitive to both nuclear shell structure and effective residual interactions. The nuclear GT excitations were studied for the mass number A = 42, 46, 50, and 54 "f-shell" nuclei in ((3)He, t) charge-exchange reactions. In the (42)Ca → (42)Sc reaction, most of the GT strength is concentrated in the lowest excited state at 0.6 MeV, suggesting the existence of a low-energy GT phonon excitation. As A increases, a high-energy GT phonon excitation develops in the 6-11 MeV region. In the (54)Fe → (54)Co reaction, the high-energy GT phonon excitation mainly carries the GT strength. The existence of these two GT phonon excitations are attributed to the 2 fermionic degrees of freedom in nuclei.

Identification of excited states in the T(z) = 1 nucleus (110)Xe: evidence for enhanced collectivity near the N=Z=50 double shell closure

Gamma-ray transitions have been identified for the first time in the extremely neutron-deficient (N=Z+2) nucleus (110)Xe, and the energies of the three lowest excited states in the ground-state band have been deduced. The results establish a breaking of the normal trend of increasing first excited 2(+) and 4(+) level energies as a function of the decreasing neutron number as the N=50 major shell gap is approached for the neutron-deficient Xe isotopes. This unusual feature is suggested to be an effect of enhanced collectivity, possibly arising from isoscalar n-p interactions becoming increasingly important close to the N=Z line.