Quantitative analysis by (p,X) and (p, γ) reactions at low energies

Production of atomic X-rays and nuclear γ-rays by bombardment with 0–3 MeV protons of thick targets is described. In the case of low-Z atomic X-rays, the absorption in the target is very large, while in the case ofK X-rays from high-Z atoms or for γ-rays, this phenomenon is negligible. Both of these reactions can be used for analysis of elements from F to U, and the sensitivities and the accuracies of the determinations are discussed. A table is given showing the γ-ray energies observed in 11 substances and the limits of sensitivity.     

Effect of cascade coincidences on the efficiency calibration of a gamma-X detector

The sensitivity on n-type gamma-X detectors for low-energy X- and -rays calls for coincidence corrections in the efficiency calibration that do not apply to the calibration of p-type detectors. Corrections were calculated for the effect of cascade coincidences between -rays, X-rays, annihilation radiation, and bremsstrahlung, for 15 radionuclides frequently used for efficiency calibration. Experimental results are presented for a -X detector with 37% relative efficiency at distances from 0.9 to 17.5 cm. After coincidence correction smooth efficiency curves were found for the energy range 12 to 2750 keV, even for the position closest to the detector.     

The emission of X-rays by fission fragments

Approximately 5% of the -ray transitions in fission fragments are internally converted, giving rise to X-rays. X-ray energies are characteristic of Z, but yields depend strongly and not smoothly on Z and A of the fragments and on time. If these biases can be accepted, X-rays can be used to identify the atomic number of fission fragments. More generally, internal conversion and X-ray emission must be interpreted in the context of detailed knowledge of -ray transitions.     

Tables of gamma rays emitted by radionuclides produced through photonuclear reactions

The tables have been prepared as an auxiliary for the interpretation of results in photoactivation analysis. They include data concerning the disintegration of radionuclides produced by (γ, n) reactions on all stable isotopes with a relative abundance greater than 1% and by (γ, p) reactions on elements withZ≤39. The γ-rays are listed in ascending order of the energies; half-lives, intensities and other useful informations are also included.     

Prompt gamma rays from triton-induced reactions on oxygen and their use for analysis

Triton-induced reactions on oxygen were studied with a view to using the prompt γ-rays for analytical purposes. Five γ-rays were found to be potentially useful, of which three had a high intensity, the n(1, 0), n(2, 0) and p(1, 0) γ-rays, the other two being the n(3, 0) and the unresolved pair α(1, 0)–α(2, 0). The γ-rays are labelled according to the conventions(a,b), wheres is the light prompt product and the γ-photon is emitted by de-excitation from levela tob in the heavy product nucleus. The method had a relative precision of 2 to 3.5% for surface oxygen concentrations from 50 to 3 μg/cm². The sensitivity with 1 900 keV tritons was 0.13 μg/cm² on surfaces of steel or copper which did not yield interfering γ-rays, but 0.45 μg/cm² on aluminium where interfering γ-rays were emitted.     

Validation of gamma-ray true coincidence summing effects modeled by the Monte Carlo code MCNP-CP

When radionuclides decay by cascading photons, the accuracy of the measured nuclide activity may be affected by true coincidence summing effects. The effects can be quantified by Monte Carlo simulations that can handle correlated γ-and X-ray emissions from a radionuclide. Analysis techniques are also available commercially to correct for the effects due to cascading γ-rays. The MCNP-CP code was used to compute the effects in high purity germanium detectors for several commonly used nuclides and geometries and the results were compared to measurements and an analysis technique. Excellent agreement in true coincidence summing corrections predicted by MCNP-CP and the analysis technique was obtained. In addition, the X-ray true coincidence summing effects were evaluated.     

Rapid determination of tungsten in rocks using183mW

A rapid method has been developed for the determination of tungsten, especially in rocks. The reaction¹⁸²W(n, γ)^183mW (T=5.3 sec), with a thermal neutron capture cross-section of 0.5 b was used. The samples were irradiated in the fast pneumatic system of the FRM, which is described briefly. The low-energy γ-rays of the isomer^183mW were measured by a high-resolving Ge(Li) detector. The sensitivity of the method is 0.1 mg tungsten with an accuracy of about 5%; the minimum concentration is 0.1–0.2% W in geological samples. The analysis time is 2 min per sample.     

Chemical effects on K and L shell production cross sections and transfer probabilities in Nb compounds

In this study, the chemical effects on σ_Ki (i = α, β), σ_Lα cross sections, K_β/K_α X-ray intensity ratios and vacancy transfer probabilities from K to L (η _KL) for pure Nb and Nb compounds were investigated. The samples were excited by 59.5 keV γ-rays from ²⁴¹Am and 5.96 keV photon energy from a ⁵⁵Fe annular radioactive sources. K and L X-rays emitted by samples were counted by an Ultra-LEGe detector with a resolution of 150 eV at 5.9 keV. While it was observed that the chemical bonding had an effect on the σ_Kβ, σ_Lα cross sections and K_β/K_α X-ray intensity ratios for compounds, it was almost negligible for σ_Kα cross section because K_α transitions (2P_3/2,1/2→1S_1/2) occurred in inner shells. It is well known that interactions between central element atom and ligands come into existence in valence state, so outer energy levels are sensitive to the chemical environment. The experimental values of σ_Kα cross section and η _KL are in good agreement with theoretically calculated and other experimental values of pure niobium, but the experimental values of the σ_Kβ, σ_Lα cross sections and K_β/K_α X-ray intensity ratios have differences for some compounds because valence electrons have different bond distances and binding energies in different compounds.     

Determination of 131mXe and 133mXe in the presence of 133gXe via combined beta-spectroscopy and delayed coincidence

The International Monitoring System for the Comprehensive Nuclear-Test-Ban Treaty will include measurements of Xe fission products. Pacific Northwest National Laboratory has developed an automated system for separating Xe from air which detects Xe fission products using a beta-gamma counting system for ^131mXe, ^133mXe, ^133gXe, and ^135gXe. Betas and conversion electrons are detected in a plastic scintillation cell containing the Xe sample. Gamma and X-rays are detected in a NaI(Tl) scintillation detector which surrounds the plastic scintillator sample cell. Two-dimensional pulse-height spectra of gamma-energy versus beta-energy are obtained. The plastic scintillator spectrum in coincidence with the 31-keV X-rays from ^131mXe. ^133mXe, and ^133gXe is a complex mixture of conversion electrons and betas. A new technique to simultaneously measure the delayed coincidence (T _1/2 = 6.27 ns) between beta-particles from ^133gXe and conversion electrons depopulating the 81-keV state in 133 Cs is being developed. This technique allows separation of the ^133gXe beta spectrum from the conversion electrons due to ^131mXe and ^133mXe and uniquely quantifies all three nuclides.     

Isomeric yields of130Sb,132Sb,134I,and136I in the thermal neutron fission of235U

Isomer yield ratios of¹³⁰Sb,¹³²Sb,¹³⁴I and¹³⁶I isomers formed in the thermal neutron fission of²³⁵U have been calculated from our previous experimental studies that led to the identification of these species. In those studies the iodine and antimony fractions formed in fission were rapidly separated and the decay of -rays belonging to each isomer pair were followed using Ge(Li) detectors and a multichannel analyzer. The isomer ratios were calculated from growth and decay considerations of these -rays. The results are compared with the recently published values obtained with an on-line isotope separator, those from LOHENGRIN, and those from model calculations. Angular momenta of fission fragments corresponding to the measured isomer yields have also been calculated.     

List-mode coincidence data analysis for highly selective and low background detection of gamma-nuclides in activated samples

Highly selective and sensitive γ-ray detection was performed by coincidence and anticoincidence event analysis after list-mode data acquisition using an HPGe spectrometer equipped with NaI(Tl) and plastic scintillation detectors. In order to obtain the most suitable detection of specific nuclides, coincidence or anticoincidence spectra could be freely constructed by extracting events with particular time and energy correlations. Although the detector arrangement of this system was the same as that of a typical Compton suppression spectrometer, background counts were drastically reduced and γ-rays of particular nuclides could be selectively detected by using γ-γ, γ-X, γ-X-X, and γ-β⁺ coincidences.     

Negative pion transfer process in a hydrogen-containing gas mixture

Annihilation γ-rays of π⁰ and pionic X-rays were measured in the gas mixtures of H₂+Z and CH₄+Z systems (Z=He, Ne, Ar and Kr). Pion capture probability of hydrogen atom was obtained from the annihilation γ-ray counts and the capture probability of Z atom was obtained from the pionic X-ray intensities. Transfer rates were determined from the data based on a combined large mesomolecular model. The transfer rates obtained were smaller than the systematics of the Russian group. Difference in the transfer rate between the gas and the liquid phases was found by a comparison of the present results with our previous ones.     

Application of fast solvent extraction processes to studies of exotic nuclides

The nucleus²³Na has been investigated by studying the primary γ-rays emitted from 53 keV neutron capture in it using a high resolution and high efficiency (100%) HPGe detector and NaI(T1) detector for anti-Compton. 24 primary γ-rays were placed in the²⁴Na, in which 3 primary γ-rays were new ones from a (n, γ) reaction, and reported for the first time. In order to obtain an exact energy calibration within 7 MeV,⁵⁶Fe(n,γ)⁵⁷Fe reaction was used at thermal neutron energy. Intensity calibration was obtained from the²⁷Al(p,γ)²⁸Si reaction atE _p=2046 keV. The neutron binding energy of²⁴Na was determined to be 6959.75 keV.     

Dependence of the Kβ/Kα intensity ratio on the oxidation state

The K/K X-ray intensity ratios were measured for pure Cr, Mn, Co and Cu belonging to the 3 d shell as well as in their compounds, to look for the influence of the chemical environment on the fluorescence yield ratios. The vacancies in the K shell created by 59.5 keV -rays from an²⁴¹Am source and the X-rays were measured using a Ge(Li) detector. A steady increase of the K/K intensity ratio was observed with increasing oxidation. The present results agree with previously published experimental data.     

Influence of chemical effect on the Kβ/Kα X-ray intensity ratios for calcium and potassium compounds

K_β/K_α X-ray intensity ratios of some K and Ca compounds were studied. The samples were excited by 5.96 keV γ-rays emitted from (50 mCi ⁵⁵Fe filtered annular) radioisotope source and characteristic K X-ray from the samples were measured by a Si(Li) detector, with a resolution of 0.16 keV at 5.9 keV. The experimental values were compared with the calculated theoretical values for K and Ca.     

On the applicability of radionuclides emitting low energy X-rays for in situ radiotracer adsorption studies

In this paper, methodology and applicability of the in situ radiotracer “thin gap” method are presented and discussed via some studies of Cr(VI) electroreduction on Pt electrode by measuring the low energy (E = 4.90 keV) X-rays of ⁵¹Cr used for labeling. Two types of scintillators, 2 mm thick β-plastic and 300 μm thick CaF₂(Eu), were tested for nuclear detection. The plastic scintillator cannot be utilized for selective measurement of the soft X-rays emitted by ⁵¹Cr, hence, it does not allow us the estimation of the surface excess of chromium containing species on Pt electrode. In contrast to this, CaF₂(Eu) is suitable for selective detection of low-energy X-rays; therefore, the radioelectrochemical cell equipped with the latter detector provides very promising measuring conditions for the extension of the radiotracer “thin gap” method towards application of the low-energy X-ray emitters.     

Computer-assisted qualitative analysis of gamma-ray spectra

A computer program is described to perform the identification of isotopes in neutron activated samples. The γ-ray energies as obtained from a Ge(Li) γ-ray spectrum are compared with those of a library, containing data for about 250 isotopes. Isotopes whose γ-ray energies match closely with the unknowns are selected as possible constituents. Unlikely attributions are then eliminated by a careful inspection of the γ-rays found. Further exploitation of half-life, the way of production and the sensitivity for the given irradiation and measurement conditions, allow the selection of the most likely constituents in the source. The results of the automated identification agree closely to those obtained by an experienced investigator. The program is written in FORTRAN IV for a PDP-9 computer with a 16 K word memory.     

K+掺杂双钙钛矿Cs2AgInCl6的发光性质

采用固相球磨法制备了K⁺掺杂双钙钛矿Cs₂AgInCl₆纳米材料,该方法无需配体辅助,绿色环保。通过X射线衍射和拉曼光谱对晶体结构进行研究,通过激发光谱、发射光谱和时间分辨光谱对其发光性能进行研究。结果表明,Cs₂AgInCl₆为立方晶体,属于Fm3m空间群,由于宇称禁戒跃迁,其荧光量子产率(PLQY)低,小于0.1%。低于60%的K⁺掺杂主要取代Ag⁺的位置,引起Cs₂AgInCl₆的晶格膨胀,消除了晶格结构的反演对称性,打破了宇称禁戒跃迁,掺杂后Cs₂AgInCl₆的光致发光强度显著增强。K⁺的最佳掺杂比例为40%,Cs₂Ag_0.6K_0.4InCl₆材料发射中心波长为640 nm,半高宽为180 nm,平均荧光寿命达到29.2 ns,PLQY达到10.5%。当K⁺掺杂比例超过60%,K⁺开始取代Cs⁺的位置,产物发生相变,出现立方相的Cs_2-xK_1+x-yAg_yInCl₆和单斜相的Cs_2-xK_1+xInCl₆产物,这些产物由于强电子-声子耦合,非辐射复合占据主导地位。     

Enhanced cell-killing effect of potassium hexachloroplatinum(IV) solution irradiated by60Co γ-rays under the presence of NH4Cl

The enhancement of cell-killing effect induced by⁶⁰Co γ-rays on the aqueous solutions of potassium hexachloroplatinum(IV) (K₂PtCl₆) irradiated in the presence of various concentrations of NH₄Cl was examined. HeLa S-3 cells were treated with the irradiated solutions for 60 minutes at 37°C, and cell survival was measured by colony forming efficiency. The mean lethal concentration (D ₀) for the cells treated with non-irradiated K₂PtCl₆ solution (1 mg/ml) was 34.5 μl/ml. However, it decreased, namely the cell-killing effect of the solution increased with increasing radiation dose up to 2.64·10⁴ Gy in the case of 0.1M NH₄Cl solution (in this condition, theD ₀ decreased to 9.6 μl/ml). No or only a slight enhancement was observed in the case of K₂PtCl₆ solutions irradiated in the presence of NaCl, (NH₄)₂HPO₄, ammonium acetate or glycine. Observations using high performance liquid chromatography (HPLC) of irradiated K₂PtCl₆ solutions revealed the formation of cis- and/or trans-diaminedichloroplatinum (IV) (DDPs(IV)). However, the observed cell-killing action of the solution was too high to be explained by the amount of both the DDPs(IV) formed by γ-rays.     

K β /K α X-ray intensity ratio in the region of 15≤Z≤22

The X-ray intensity ratioK /K has been measured by using a 10 mCi⁵⁵Fe source (MnK X-rays) and high resolution Si(Li) detector system coupled to a computer-controlled multichannel analyzer over the range of 15Z22. Corrections have been made to the measured relative intensities (K andK X-rays) for self-absorption in the sample, air, Be-window absorption and detection efficiency. The results are compared with those of other experiments and with the Scofield calculations.