Proton-hole states in Bi From the Po (t, α) reaction

The ²¹⁰Po(t, α)²⁰⁹Bi reaction has been studied at 20 MeV triton energy with an overall resolution of 20 keV FWHM. Absolute cross sections were established by a comparison of the (t, α) intensities to elastic triton scattering. The three lowest single-proton states in ²⁰⁹Bi were observed and spectroscopic factors were extracted from the measured cross sections by DWBA analysis. Starting at 2.43 MeV, six levels were strongly excited. These states have large 2p-1h proton components. The spectroscopic factors were extracted by a comparison of ²¹⁰Po(t, α) cross sections to ²⁰⁸Pb(t, α)²⁰⁷T1 single-proton-hole cross sections measured previously at the same bombarding energy. The observed states and their properties were analyzed within the framework of the particle- (or hole) vibration coupling model. Surface vibrational states in ²⁰⁸Pb coupled to single protons as well as the proton pair addition modes (states in ²¹⁰Po) coupled to a proton-hole were included in the analysis.     

Levels of 209Po and 211Po populated in one-neutron stripping and pickup from 210Po

Energy levels of ²⁰⁹Po have been populated with the ²¹⁰Po(d, t)²⁰⁹Po and ²¹⁰Po(p, d)²⁰⁹Po reactions at bombarding energies of 17.0 and 17.8 MeV respectively. Fifteen levels were observed below 2.7 MeV of excitation. Energy levels of ²¹¹Po were populated with the ²¹⁰Po(d, p)²¹¹Po reaction, also at 17.0 MeV. Thirty-five levels, almost all new, were observed below 3.9 MeV of excitation. Comparison of experimental angular distributions with DWBA calculations allowed l-value assignments and extraction of spectroscopic factors for many levels. In ²⁰⁹Po the observed level structure is well described in terms of a simple particle-vibration coupling model. In ²¹¹Po the level structure is more complex and the simple model is not adequate.     

Two-proton multiplets in Po

The ²⁰⁹Bi(α,t)²¹⁰Po reaction at 45 MeV has been used to study ²¹⁰Po. Many new levels have been observed and proton configurations are suggested for the lowest three multiplets.     

The γ-Decays of 210Po-Levels from the (3He, d*γγ)-Reaction

An in-beam experiment with the subcoulomb reaction ²⁰⁹Bi(³He, d^*γγ)²¹⁰Po at 20.5 MeV was performed with two Euroball Cluster detectors in Cologne. It closed the gap between the low energy levels of the level-scheme and the high energy levels found in ²⁰⁹Bi(³He, d)²¹⁰Po and ²⁰⁸Pb(⁴He, t)²¹⁰Po particle experiments. New branchings have been found and the (³He, d^*γγ) reaction below the coulomb-barrier has been used successfully. Received: 17 December 1998 / Revised version: 27 January 1999     

Experimental study of excitation functions and isomer ratios for 211, 212Po

Excitation functions have been measured for ground states and isomers populated in the ²⁰⁸Pb(α, n)²¹¹Po, ²⁰⁹Bi(α, np)²¹¹Po, ²⁰⁹Bi(α, p)²¹²Po and ²⁰⁹Bi(α, n)²¹²At reactions for α-beams ranging from 45 MeV to 172.5 MeV. The experimental results have been compared with theoretical calculations assuming direct and preequilibrium reaction mechanisms, respectively. It is found that the experimental excitation functions can be reproduced satisfactorily by calculations in the framework of the preequilibrium model. Isomer ratios have been extracted from the data as well. Their energy dependence can be reproduced by an optical-model calculation for beam energies larger than about 60 MeV.     

Simple formulae for heavy ion subcoulomb transfer probabilities. Application to one and two-proton transfers in bismuth

A simple analytical formula is given to express the transition probability in a quasi-elastic transfer reaction. This formula is derived from the DWBA amplitude, using assumptions based on the fact that the main contribution to the DWBA integral comes from a narrow domain of distances of approach. Recoil effects are taken into account. This method is applied to calculate the excitation functions for one and two-proton transfer reactions induced in²⁰⁹Bi by heavy ions, below and near the barrier. The curves obtained are compared to the excitation functions measured for the production of residual²¹⁰Po and²¹¹At. The corresponding transfer reactions involve excitation energiesE ^* of the residue lying in the range 0–8 MeV. This excitation energy is taken as a free parameter in the calculation, and the valuesE _opt ^* which lead to the best agreement between the calculated and experimental curves are consistent with the classical values for the optimum reactionQ-values. Nuclear Reactions. Simplified transition probability for quasi-elastic transfer. Calculatedσ(E) ²⁰⁹Bi(X, Y)²¹⁰Po,²¹¹At,X=¹⁴N,¹⁶O,¹⁹F,⁴⁰Ar,⁴⁰Ca,⁵⁶Fe,⁶³Cu near threshold. Compared experimental data. Deduced optimum excitation energy.     

210Po in popular medicinal herbs from Poland

Herbs are an important part of traditional medicine in Poland. Therefore, the aim of this study was the determination of polonium ²¹⁰Po in 48 selected medicinal herb samples from the Polish market. The activity concentrations of ²¹⁰Po were measured using alpha spectrometry. The activity concentration of ²¹⁰Po was in the range from 0.3?±?0.1 to 28.2?±?0.4 Bq kg^–1. The obtained results were compared with corresponding studies conducted worldwide. A higher ²¹⁰Po activity concentration was observed in the above-ground part of plants. The obtained results show that the highest ²¹⁰Po activity concentration was observed in evergreen plants and winter-hardy plants. Yet even infusions with 2 g of the most contaminated herbs examined were considered to be radiologically safe.     

The reaction 48Ca + 238U → 286112* studied at the GSI-SHIP

The fusion reaction of ⁴⁸Ca projectiles with ²³⁸U target nuclei was studied at the velocity filter SHIP of GSI in Darmstadt. Two decay chains were measured, which fully confirm data that were previously assigned to the isotope ²⁸³112 in experiments at the Flerov Laboratory in Dubna. Two other events are consistent with a 50% spontaneous-fission (SF) branch of this isotope. The mean value obtained for the half-life of ²⁸³112 is (6.9 ^+6.9 _-2.3 s, the α energy is (9.520±0.015) MeV, and the total kinetic energy (TKE) of SF is (238±14) MeV. The half-life of the α decay daughter nucleus ²⁷⁹Ds is (0.18 ^+0.32 _-0.07 s, and the TKE of SF is (210 ⁺³² _-11 MeV. The cross-section deduced from all four events is (0.72 ^+0.58 _-0.35 pb , measured at an excitation energy of 34.6MeV of the compound nucleus ²⁸⁶112.     

On the β-decay 210Bi(RaE) → 210Po(RaF)

It was the aim of the present work to extract nuclear wave functions directly from experimental data of β-transitions. As a favourable example the 1^? (1.153 MeVβ^?)0⁺ β-transition of ²¹⁰Bi(RaE) was studied. The results obtained are compared with theoretical wave functions and good quantitative agreement, especially for the ground state of the daughter nucleus ²¹⁰Po, was found. It is explicitely demonstrated how, in this case, the higher order terms of the transition matrix elements contribute. The results for the matrix element ratios μ and Λ are discussed. In particular it is shown that it is not possible to test CVC theory by examining Λ.     

Asymmetric mass distribution from the fusion-fission reaction40Ar+243Am

The mass distributions and total c.m. kinetic energies of fission fragments formed in the reaction⁴⁰Ar+²⁴³Am at bombarding energies of 214, 222, 240 and 300 MeV have been measured using the angular correlation method. Angular distributions and anisotropy for 222 and 300 MeV have also been obtained. A symmetric mass distribution corresponding to the decay of a highly excited compound nucleus was obtained at 300 MeV bombarding energy. However, with decreasing bombarding energy the fission fragment mass distribution becomes asymmetric, the most probable heavy fragment mass being about 200–210 amu.     

Reactions on 209Bi induced by intermediate energy protons and the effect of direct reactions

Excitation functions and ranges of recoil nuclei in the ²⁰⁹Bi(p, 3n)²⁰⁷Po, ²⁰⁹Bi(p, 4n) ²⁰⁶Po and ²⁰⁹Bi(p, p3n)²⁰⁶Bi reactions have been measured for incident energies from 18 MeV up to 52 MeV. It has been found that the recoil ranges in (p, p3n) reactions are rather shorter than those in (p, 4n), and that beyond E_p = 40 MeV the high energy tail of the excitation function for (p, p3n) is roughly flat, in contrast to the decreasing tail for (p, 4n). A theoretical analysis of the excitation functions and of the nuclear recoil ranges has been made. It has been found that in (p, p3n) reactions the direct process plays a very important part in the reaction mechanism. It is also found that the reaction mechanisms of (p, 3n) and (p, 4n) reactions should be interpreted by means of an admixture of the equilibrium compound process and the pre-equilibrium decay process at bombarding energies up to 40 MeV and 50 MeV, respectively, and that the direct process seems to appear at bombarding energies higher than these respective energies.     

π− Production in16O +27Al at 38, 65 and 93 MeV/u

Negative pion production cross-sections are measured at 38, 65 and 93 MeV per nucleon in O + Al reaction. Rough estimations of the total cross sections are given and compared to previous neutral pion data. Double differential cross sections at 93 and 65 MeV/u show enhancement for pions with velocity close to the beam. At variance no effect is observed at 38 MeV, where π^? and π⁰ distributions are identical. Fewπ ⁺ detected at 38 MeV support this result. This indicates that at the lowest incident energy nearly the whole projectile participates in the production reaction.     

Energieverlust und Reichweite von α-Teilchen in Bor im Energiebereich von 0,2 bis 5,3 MeV

With a scintillation spectrometer the air equivalent of boron for α-particles has been measured as a function of the energy. The boron foils (50?120 μg·cm^?2) were evaporated onto thin mica. The α-particle energy was set to between 0.2 and 5.3 MeV by letting the particles of a²¹⁰Po-α-source pass through air. With known data for the energy loss in air the range and stopping power in boron have been determined. The error of each measured datum is about 2%.     

On absolute values of α-decay rates

A possible way to remove the discrepancy between calculated and measured α-widths is discussed. The decay rates of ²¹²Po and ²¹⁰Po are computed with the help of shell-model wave functions for parent and daughter nucleus.     

Study of the excitation function fluctuations of the dissipative28Si+48Ti binary collision in the incident energy interval from 206.9 MeV to 213.8 MeV

It is shown that the Partially Overlapping Molecular Level Model (POMLM) accounts for the experimental results of the dissipative²⁸Si +⁴⁸Ti collision around 210 MeV incident energy. The general trend of the properties of the fluctuations as well as the average angular distributions are reproduced by the same set of main parameters. A general consistency is also found between the present data and the data obtained in previous work on the same colliding system performed at lower incident energy (around 123 MeV).     

Energy dependence of the optical model parameters for 3He ions scattered from 40Ca and 58Ni

The differential cross sections for the elastic scattering of ³He ions on targets of ⁴⁰Ca and ⁵⁸Ni have been measured at incident energies of 27.7, 51.4, 73.2 and 83.5 MeV. The results of optical model analyses showed that only one unique potential (J_R ≈ 330 MeV · fm³) with a surface absorptive term can provide acceptable fits to the large angle elastic scattering cross sections at 83.5 MeV. The particular geometrical set found at 83.5 MeV could not, however, give an adequate fit to the data with energy less than 40 MeV. Subsequent analyses indicated that a break in the energy dependence of the real potential is observed for the low energy data. Explicit energy dependent terms were obtained by fitting all the data simultaneously. These phenomenological potentials were also compared with the folded nucleon-nucleus potential. The influence of the α-particle channels on the elastic scattering of ³He ions at 83.5 MeV was also examined.     

Polonium in cigarette smoke and radiation exposure of lungs

Polonium (²¹⁰Po), the most volatile of naturally-occurring radionuclides in plants, was analysed in three common brands of cigarettes produced in Portugal. The analyses were carried out on the unburned tobacco contained in cigarettes, on the ashes and butts of smoked cigarettes and on the mainstream smoke. ²¹⁰Po in tobacco displays concentrations ranging from 3 to 37 mBq g⁻¹, depending upon the cigarette brand. The ²¹⁰Po activity remaining in the solid residue of a smoked cigarette varied from 0.3 to 4.9 mBq per cigarette, and the ²¹⁰Po in the inhaled smoke varied from 2.6 to 28.9 mBq. In all brands of cigarettes tested, a large fraction of the ²¹⁰Po content is not inhaled by the smoker and it is released into the atmosphere. Part of it may be inhaled by passive smokers. Depending upon the commercial brand and upon the presence or absence of a filter in the cigarette, 5 to 37 % of the ²¹⁰Po in the cigarette can be inhaled by the smoker. Taking into account the average ²¹⁰Po in surface air, the smoker of one pack of twenty cigarettes per day may inhale 50 times ²¹⁰Po than a non smoker. Cigarette smoke contributes with 1.5 % to the daily rate of ²¹⁰Po absorption into the blood, 0.39 Bq d⁻¹, and, after systemic circulation it gives rise to a whole body radiation dose in the same proportion. However, in the smoker the deposition of ²¹⁰Po in the lungs is much more elevated than normal and may originate an enhanced radiation exposure. Estimated dose to the lungs is presented and radiobiological effects of cigarette smoke are discussed.     

<Superscript>210</Superscript>Pb and <Superscript>210</Superscript>Po in fossil fuel combustion at the Šoštanj thermal power plant (Slovenia)

The main aim of the present study was to evaluate ²¹⁰Pb and ²¹⁰Po emissions from the ?o?tanj TPP and to evaluate their mass balance in unit 4. Samples of coal, fly ash, slag and flue gases were analysed for ²¹⁰Pb and ²¹⁰Po content. The results showed that these radionuclides are mostly concentrated in ash (71% and 81% for ²¹⁰Pb and ²¹⁰Po, respectively). Only a small part of the input activity was detected in flue gases. The activities of ²¹⁰Pb and ²¹⁰Po in unit 4 were from 1.1 to 2.7 Bq m^?3 and from 0.37 to 0.56 Bq m^?3, respectively. The mass balance of the two radionuclides in unit 4 show only 6 and 10% differences between the annual activities of the input and output samples.     

Production parameters of the therapeutic 105 Rh radionuclide using medium energy cyclotron

Production cross-sections of the therapeutic ¹⁰⁵Rh radionuclide from proton-induced reactions on natural palladium target were measured using stacked-foil activation technique combined with high resolution ??-ray spectrometry at the MC50 cyclotron of the Korea Institute of Radiological and Medical Sciences. Note that cyclotron production of the ¹⁰⁵Rh radionuclide from natural palladium target was measured here for the first time. Results are compared with the theoretical values obtained using the model codes TALYS and ALICE-IPPE. Thick target integral yields for the investigated ¹⁰⁵Rh radionuclide were deduced from the threshold energy to 40?MeV. Measured data of the ¹⁰⁵Rh radionuclide are important because of its potential applications in nuclear medicine and/or therapeutic purposes. Optimal production circumstances for the therapeutic ¹⁰⁵Rh radionuclide using a cyclotron are discussed elaborately.