Dose assessment of bremsstrahlung induced by beta-emitting radioisotopes of uranium-238 series and lead in human tissues

In the natural uranium-238 decay series, pure beta isotopes such as ²³⁴Th, ²³⁴Pa, ²¹⁴Pb, ²¹⁴Bi, ²¹⁰Pb and ²¹⁰Bi are released. The few lead isotopes such as ²¹¹Pb, ²¹²Pb, ²¹³Pb and ²¹⁵Pb are good beta emitters. In certain nuclear reactions of reactor these isotopes are released. These beta isotopes have maximum beta energies, which induce the bremsstrahlung radiation. The bremsstrahlung component of these beta isotopes has been traditionally ignored in dosimetry calculations. The shapes of bremsstrahlung spectra are a basic ingredient in the understanding and quantification of beta-ray dosimetry. The bremsstrahlung spectra produced by these high-energy isotopes such as ²³⁴Th, ²³⁴Pa, ²¹⁴Pb, ²¹⁴Bi, ²¹⁰Pb, ²¹⁰Bi, ²¹¹Pb, ²¹²Pb, ²¹³Pb and ²¹⁵Pb in bone, muscle and teeth are studied, and the computed spectral distributions are presented. The spectral shapes are primarily responsible for variations in the shapes of depth–dose distributions. They are intended to provide a quick and convenient reference for spectral shapes and to give an indication of the wide variation in these shapes. The evaluated beta bremsstrahlung dose as a function distance for the studied nuclides is also presented. The efficiency, intensity and dose rate of bremsstrahlung induced by beta isotopes of natural uranium-238 decay series and beta-emitting lead isotopes in human tissues such as brain, breast, heart, kidney, liver, muscle, pancreas and bone have also been studied in the present investigation. The values of bremsstrahlung dosimetric parameters are low for pancreas, but they are high for bone. For all studied tissues these parameters are high for ²³⁴Pa, but low for ²¹⁰Pb.     

Isovector correlations and pion single charge exchange reactions in light nuclei

The reactions ⁷Li(π⁺, π⁰)⁷Be(g.s.), ⁷Li(π⁺, π⁰)⁷Be1(429keV) and ¹³C(π⁺, π⁰)¹³N(g.s.) are treated in DWIA, including corrections arising from two-step processes in which an intermediate state is reached in the course of the charge exchange. The distortions are introduced by means of a first-order optical potential; no special assumptions of extreme high energy limits are made. The closure sum over intermediate states in the two-step charge exchange mechanism leads to an isovector two-particle correlation function whose properties for p-shell nuclei are discussed in detail. Consequences of the introduction of effective transition operators for the single-step mechanism, with and without spin-flip, and for the two-step contribution are discussed, as are the allowable modifications in nuclear shell radii consistent with present knowledge of Coulomb energies. Comparison is made with experiment — in the case of the separated ⁷Be states, for the first time — and with other theoretical approaches.     

EPR parameters and defect structures of the off-center Ti ion on the Sr site in neutron-irradiated SrTiO3 crystal

The EPR parameters (g factors and hyperfine structure constants A) for the tetragonal Ti³⁺ center in cubic phase and the rhombic Ti³⁺ center in tetragonal phase in the neutron-irradiated SrTiO₃ crystals are calculated from the third-order perturbation formulas of EPR parameters for d¹ ions. These low-symmetry Ti³⁺ centers in both phases of SrTiO₃ are due to the Ti³⁺ ion at “off center” on the Sr²⁺ site. From the calculation, the defect models (including the direction and magnitude of the Ti³⁺ off-center displacement) of the two Ti³⁺ centers in SrTiO₃ are estimated and the EPR parameters of both Ti³⁺ centers are reasonably explained on the basis of the defect models. The results are discussed.     

类铍离子低激发态等电子系列的能量、精细结构和超精细结构

采用多组态相互作用方法及Rayleigh-Ritz 变分方法，并考虑相对论修正和质量极化效应，获得了类铍离子等电子系列（Z=4-10）低激发态1s²2p2p ¹D^e和1s²2p3p ³P^e的相对论能量。同时还计算了精细结构和超精细结构。计算结果与其他理论和实验符合的很好。     

Production of P-wave charm and charm-strange mesons in hadronic Z0 decays

Results are presented on the production of excited charm and excited charm-strange mesons in hadronic Z⁰ decays. The results are obtained from approximately 4.3 million hadronic Z⁰ decays, collected on or near the Z⁰ resonance using the OPAL detector at LEP. The D⁰ ₁(2420) and D^*0 ₂ (2460) mesons are reconstructed in the D^*+π^-. final state and their separate production rates in charm fragmentation and in weak decays of b-hadrons are determined. Assuming that the decay widths of these mesons are saturated by the allowed D*π and Dπ final states, the charm hadronization fractions and the inclusive branching ratios of b-hadrons to these neutral P-wave charm mesons are determined to be     

Cold reaction valleys in the radioactive decay of superheavy 286112, 292114, and 296116 nuclei

Cold reaction valleys in the radioactive decay of superheavy nuclei ²⁸⁶112, ²⁹²114, and ²⁹⁶116 are studied taking Coulomb and Proximity Potential as the interacting barrier. It is found that in addition to alpha particle, ⁸Be, ¹⁴C, ²⁸Mg, ³⁴Si, ⁵⁰Ca, etc. are optimal cases of cluster radioactivity since they lie in the cold valleys. Two other regions of deep minima centered on ²⁰⁸Pb and ¹³²Sn are also found. Within our Coulomb and Proximity Potential Model half-life times and other characteristics such as barrier penetrability, decay constant for clusters ranging from alpha particle to ⁶⁸Ni are calculated. The computed alpha half-lives match with the values calculated using Viola-Seaborg-Sobiczewski systematics. The clusters ⁸Be and ¹⁴C are found to be most probable for emission with T _1/2 < 10³⁰ s. The alpha-decay chains of the three superheavy nuclei are also studied. The computed alpha-decay half-lives are compared with the values predicted by Generalized Liquid Drop Model and they are found to match reasonably well.     

Coulomb forces in the three-body problem with application to direct nuclear reactions

Faddeev equations are considered in the case of three charged particles interacting with both separable nuclear two-body interactions and also including Coulomb forces. Modified Faddeev equations with Coulomb Green's functions are introduced. The three-body amplitudes are given into pure Coulomb and distorted-Coulomb amplitudes. Introducing a decomposition in the angular momentum states, a set of three-body integral equations is obtained. The effect of pure coulomb amplitudes is studied in direct nuclear reactions and found to give a large contribution to the cross sections. The three-body integral equations obtained are applied for direct nuclear reactions. The angular distributions for¹²C(⁶Li,d)¹⁶O,¹⁶O(⁶Li,d)²⁰Ne, and¹²C(⁶Li,α)¹⁴N transfer reactions are calculated as well as for the⁶Li elastic scattering on¹²C. From the good agreement between the theoretically calculated and experimental data, better spectroscopic factors are extracted. The effect of including Coulomb forces in the three-body problem is found to improve the results by about 16.26%.     

Behavior of the giant-dipole resonance in 120Sn and 208Pb at high excitation energy

The properties of the giant-dipole resonance (GDR) are calculated as a function of excitation energy, angular momentum, and the compound nucleus particle decay width in the nuclei ¹²⁰Sn and ²⁰⁸Pb, and are compared with recent experimental data. Differences observed in the behavior of the full-width-at-half-maximum of the GDR for ¹²⁰Sn and ²⁰⁸Pb are attributed to the fact that shell corrections in ²⁰⁸Pb are stronger than in ¹²⁰Sn, and favor the spherical shape at low temperatures. The effects shell corrections have on both the free energy and the moments of inertia are discussed in detail. At high temperature, the FWHM in ¹²⁰Sn exhibits effects due to the evaporation width of the compound nucleus, while these effects are predicted for ²⁰⁸Pb.     

Ω− non-leptonic decays

Non-leptonic decay rates for Ω^? are calculated in a model where strong interactions introduce new ΔI = 1/2 operators in the effective hamiltonian. Both Ω^?→Ξ^0,?π^?,0 and Ω^?→Λ⁰K^? are predicted to be nearly parity conserving. ΔI = 1/2 contributions are found to dominate the sum of the pionic rates, while ΔI = 3/2 contributions are non-negligible in each of them. Rough agreement in magnitude with experimental data is obtained.     

Measurement of the reactions K+d → K+d and K+d → p+pn and an investigation of elastic K+-nucleon scattering at 4.6 GeV/c

The coherent elastic reaction K⁺d → K⁺d and the break-up reaction K⁺d → K⁺pn are studied in a K⁺d experiment at 4.6 GeV/c which the CERN 2 m bubble chamber. Partial and differential cross sections are given and the slopes of the differential cross sections are determined. The results for the reaction K⁺d → K⁺p(n_s), where n_s denotes the spectator neutron, are compared with those of the reaction K⁺p → K⁺p on free protons. Combining our data with existing data on the reactions K⁺d → K⁰pp and K⁺p → K⁺p, parameters of the elastic K⁺-nucleon scattering at 4.6 GeV/c are determined in the framework of the Glauber model. The D-wave of the deuteron and spin-flip effects are taken into account.     

Transport of excess charge carriers in liquid and solid hydrogen

The temperature dependence of the drift mobility of excess charge carriers in liquid and solid hydrogen has been investigated. Both negative and positive carriers are observed in the liquid with mobilities ～ 5 × 10^-3 cm² V^-1 sec^-1 at 15 K; the mobile carriers in the solid are believed to be negatively Charged with a mobility ～ 6 × 10^-6 cm² V^-1 sec^-1 at 13 K. The mechanisms of charge localization and transport are discussed.     

Spin-parity assignments of excited states in 12C

The reaction ¹²C(α, α')¹²C¹(3α) is observed by using 90 MeV a-particles in ionographic matter. The energies of the three α-particles from the break-up of ¹²C¹ are plotted in Dalitz diagrams. The density distributions for the three α-particles in the diagrams are calculated by assuming the spins and parities for the states in ¹²C¹(3α). The spin-parities for the states are assigned by comparing the observed density distributions with those calculated.     

Semiclassical analysis of α-transfer reactions

Semiclassical concepts are used to gain insight into α-transfer reactions. These reactions, interpreted as one-step direct reactions on the basis of DWBA analyses, are treated in analogy with single nucleon transfer reactions for which it is known that semiclassical methods are successful. In this case however the probability of transfer appears to be greatest at a distance of closest approach which is larger than the grazing distance by the order of the α-particle radius. This increase in the effective “grazing” distance is interpreted as a manifestation of the α-particle size at the time of transfer. Angular distributions are calculated semiclassically for the reactions ²⁰⁸Pb(¹⁶O, ¹²C)²¹²Po at 93 MeV and ⁴⁰Ca(¹²C, ⁸Be)⁴⁴Ti at 45 MeV lab energy. They are seen to give a reasonable fit to experiment. Partial wave amplitudes for transfer are also studied.     

Three-body muon-transfer collisions from hydrogen isotope to He<Superscript>2+</Superscript> and Li<Superscript>3+</Superscript> ions

The muon transfer rates from hydrogen isotopes (p,d) to ^3,4He²⁺ and ^6,7Li³⁺ ions are calculated in the hyperspherical close coupling method. Well converged results are obtained. The present rates are comparable to those of existing calculations for He²⁺, but they are much larger for Li³⁺. The resonance parameters are also calculated for resonances near the (Hμ)_1s threshold.     

The competition between different degrees of freedom in the structure of the quintet states of negative parity of some even-even Sn isotopes

Levels 2⁺, 3⁻, 1⁻, 2⁻, 3⁻¹, 5⁻ are interpreted as eigenvalues of a boson expanded Hamiltonian containing a shell model term, pairing, and quadrupole-quadrupole and octupole-octupole interaction. The expansion is performed in terms of standard RPA noncollective phonons and the so-called correlated phonons which are related to the RPA collective phonons by a canonical transformation whose parameters are determined so that the energy of the ground state is minimum. The noncollective degrees of freedom are included via an effective Hamiltonian depending on energy. Formalism is applied to ¹¹⁴Sn, ¹¹⁶Sn, and ¹¹⁸Sn. Also, transition probabilities and quadrupole moments are calculated. Results are compared with experimental data as well as with the previous theoretical calculations.     

Analysis of two-nucleon transfer reactions by heavy ions on the basis of one- and two-step processes

Two-nucleon transfer reactions induced by heavy ions are analyzed on the basis of the one-step (simultaneous) and two-step (successive) transfer processes. The reactions considered here are ¹²C(¹⁸O, ¹⁶O)¹⁴C, ⁴⁸Ca(¹⁸O, ¹⁶O)⁵⁰Ca and ⁴⁸Ca(¹⁶O, ¹⁴C)⁵⁰Ti. Finite-range calculations with full recoil are performed for both processes. The results of the calculations show that the two processes are of roughly equal importance and both are needed to reproduce the experimental angular distributions as well as the absolute magnitude of the cross sections. The dependence of the cross section on the choice of the structure wave functions and the relative importance of the intermediate states in the two-step process are also discussed.     

Five-nucleon spectroscopic amplitudes for 1p-shell nuclei

Spectroscopic amplitudes of the ⁵He or ⁵Li cluster in the ground and first excited states are given for lp-shell nuclei. These Spectroscopic amplitudes are calculated with the aid of intermediate-coupling wave functions of initial and final nuclei. Sum rules for pickup and stripping reactions are presented. The selectivity in excitation of the final states in pickup and stripping reactions of the ⁵He or ⁵Li cluster for some targets are discussed.     

Electromagnetic decay of excited 0+ states in 64, 66, 68Zn

The E0 and E2 transitions depopulating the excited 0⁺ states in ^64,66,68Zn are investigated. Several methods of γ-ray, conversion-electron and internal-pair spectrometry are employed, including a new time measurement technique. A total of 5 E0 transitions are observed and the monopole strengths ρ²(0_i⁺ → 0_i⁺) for most of them are extracted. The results and the nature of the excited 0⁺ states are discussed in terms of several nuclear models.     

Spin distributions in the vibrational excitations of closed-shell nuclei

Self-consistent Hartree-Fock and RPA calculations with the Skyrme-type interaction SGII are used for a systematic investigation of the 1⁺ and the triplet 0^?, 1^?, 2^? states in ⁴⁰Ca and ²⁰⁸Pb. Response functions to spin-dependent multipole operators are calculated and the particle-hole structure of the spin-dependent collective states is studied. Collective spin-dependent 0^? and 1^? states above the giant dipole resonance as well as a collective spin-independent 2^? state (twist mode) are identified. Transition spin and current densities are calculated for the collective excitations and found to be useful for the study of these excitation modes.     

Determination of Separated Plutonium,Americium and Curium in Environmental Samples by Sequential Extraction Techniques

A simple, reliable and practical radiochemical method for sequential isolation and determination of plutonium, americium and curium in a wide variety of environmental samples including soils, river sediments and water was developed. The isotopes determined are: ²³⁸Pu, ^239,240Pu, ²⁴¹Am, ²⁴²Cm and ²⁴⁴Cm. The methods involve leaching of soil or sedimental samples with concentrated nitric acid using a pressure digestion technique. Subsequent concentration and separation of nuclides of interest from major matrix elements and other interfering alpha-emitters are carried out by coprecipitation with ferric hydroxide and solvent extractions. Sources suitable for alpha-spectrometry are prepared by electrodeposition from acidic ammonium chloride solution. ²⁴²Pu and ²⁴³Am are used as tracer isotopes of plutonium and americium-curium elements, respectively. Some results of analysis of soils, sediments and water are given. The alpha peaks from ²³⁸Pu, ^239,240Pu and ²⁴²Pu as well as ²⁴¹Am, ²⁴⁴Cm, ²⁴²Cm and ²⁴³Am are well resolved. The entire analytical procedures for plutonium, americium and curium are completed in less than sixteen hours.