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1.
Thick-target yield of γ-rays emitted in the reactions14N(p,p′γ1)14N and15N(p,αγ1)12C were measured as a function of bombarding energy in order to select the conditions favoring the employment of these reactions
in nitrogen isotopic analysis. The applicability of these reactions in the determination of relative as well as absolute nitrogen
isotopic abundances was demonstrated at 4.3 MeV bombarding energy.
Supported in part by the International Atomic Energy Agency, Vienna, Austria. 相似文献
2.
M. L. Böttger D. Birnstein W. Helbig 《Journal of Radioanalytical and Nuclear Chemistry》1980,58(1-2):183-187
The energy-dependent range of charged particles in activation analysis according to the reaction12C(d,n)13N permits the method to be applied to carbon determination in model epitaxial layers of sufficient thickness. We investigated
100 μm epitaxial layers of the n-type and undoped 50 μ layers as to p− Czochralski substrates. Deuterons were slowed down with Cu and Ta foils having a limiting energy of 13.5 MeV, to 4.2 MeV
and 2.9 MeV, respectively. In the resulting activation depths of 52 and 102 μm, the sensitivity of the method, which is 3·1014 at ·cm−3C at Ed=10 MeV in silicon, is reduced to 25% and 10%, respectively. An optimal flux of 0.9 μA·cm−2 was maintained. After irradiation, 20 or 10 μm were etched off. The sample was inductively fused at 1500 K in a Pb3O4/B2O3 mixture.13N was passed with He as carrier gas into an absorption vessel kept at 77 K, and its activity was measured in γ, γ-coincidence. 相似文献
3.
K. Shikano A. Mori M. Shimizu T. Ohtsuki H. Yuki K. Masumoto 《Journal of Radioanalytical and Nuclear Chemistry》2005,266(2):211-216
Summary We have studied the photon activation analysis of carbon in InF3-based fluoride, chalcogenide and tellurite glasses for fiber amplifiers, and especially the nuclear interference from a matrix
produced by (γ,n), (γ,2n), (γ,p) and (n,γ) reactions and a flow method for the rapid and simple separation of 11C. A chemical separation technique is indispensable for determining carbon, because seventeen radionuclides are observed in
these glasses. The flow method can sequentially be undertaken, the fusion of an irradiated sample with an oxidizer, the conversion
of 11C into 11CO2, and the absorption of 11C in ethanolamine solution. We used a mixture of Pb3O4 and B2O3 as the oxidizer. There is interference with the 11C measurement because 18F and 68Ga are produced in fluoride and chalcogenide glasses by the 19F(γ,n), 23Na(γ,αn) and 69Ga(γ,n) reactions, respectively, and also absorbed in ethanolamine solution. Therefore, this flow method can only be applied
to tellurite glasses. The chemical yield provided by the flow method was close to 100% when determining carbon in Japanese
Iron and Steel Certified Reference Materials (JSS) by using lithium carbonate as a standard sample. We determined that the
carbon concentrations in four kinds of tellurite glass were 7 to 14 ppm. 相似文献
4.
W. D. James W. D. Ehmann C. E. Hamrin L. L. Chyi 《Journal of Radioanalytical and Nuclear Chemistry》1976,32(1):195-205
The feasibility of using fast neutron (14 MeV) activation analysis techniques for the determination of oxygen and nitrogen
in coal has been investigated. Conditions that favor instrumental neutron activation analysis (INAA) include the absence of
problems associated with sample dissolution and the capability of extremely rapid analyses as compared to older techniques
such as the Kjeldahl method for nitrogen. Most previous oxygen determinations have been by difference after major component
analyses. In the present study, oxygen was determined in sized coal and its low temperature ash (LTA) with the difference
representing the organic oxygen content. Both the oxygen and nitrogen analyses employ a multiscaling technique with the former
based on the16O(n, p)16N reaction, while the latter utilizes the annihilation radiation produced by the product of the14N(n, 2n)13N reaction. The high-energy gamma-radiation associated with the decay of16N was essentially free of spectral interferences for coal analysis, although fluorine could cause a primary interference if
the F/O ratio exceeds 0.02. In the nitrogen work, experiments were performed to determine correction factors to account for
the effects of the12C(p, γ)13N and13C(p, n)13N “knock-on” reactions and the39K(n, 2n)38K reaction which produce interfering β+ emitting radionuclides. Data are presented for oxygen in Western Kentucky No. 9 and No. 11 coal and coal ash and for nitrogen
in eleven different coals. 相似文献
5.
P. M. Pollard J. W. McMillan D. J. Malcolme-Lawes 《Journal of Radioanalytical and Nuclear Chemistry》1982,70(1-2):349-370
Sensitive and selective nuclear reaction methods have been sought for the nuclear microprobe measurement of the spatial distributions
of13C and13C/12C ratios. The13C(α, n)16O reaction, with neutron detection, is the most selective for13C, and has a sensitivity of ca. 100 ppm. The reactions13C(d, p)14C and12C(d, p)13C, with proton detection, are the most sensitive for the simultaneous measurement of13C and12C, with detection limits of 30 and 2 ppm respectively. Less sensitive alternative reaction pairs are;13C(3He, p)15N and12C(3He, p)14N;13C(d, nγ)14N and12C(d, pγ)13C;13C(3He, pγ)15N and12C(3He, pγ)14N. The conditions governing their use, particularly light element interferences, are detailed. 相似文献
6.
W. J. Naudé M. Peisach R. Pretorius P. J. Strebel 《Journal of Radioanalytical and Nuclear Chemistry》1968,1(3):231-241
Carbon, nitrogen and oxygen were determined in gases by time-of-flight spectrometry of prompt neutrons from the respective
reactions12C(d, n)13N,14N(d, n)15O and16O(d, n)17F, produced by a pulsed beam of deuterons of 2 MeV (for nitrogen) or 3 MeV. The analysis is non-destructive and requires about
15 min. per sample. The relative standard deviation for all three elements was about ±3%. Detection limits, using a total
irradiation current of 20 millicoulombs, for carbon, nitrogen and oxygen, respectively, were 6·10−8 g, 2·10−7 g and 1.7·10−7 g per cm2 cross-sectional area of irradiating beam. 相似文献
7.
Boron carbide is widely used as industrial material, because of its extreme hardness, and as a neutron absorber. As part of
a round-robin exercise leading to certification of a new reference material (ERM-ED102) which was demanded by the industry
we analysed nitrogen in boron carbide by inert gas fusion analysis (GFA) and instrumental photon activation analysis (IPAA)
using the 14N(γ,n)13N nuclear reaction. The latter approach is the only non-destructive method among all the methods applied. By using photons
with energy below the threshold of the 12C(γ,n)11C reaction, we hindered activation of matrix and other impurities. A recently installed beam with a very low lateral activating
flux gradient enabled us to homogeneously activate sample masses of approximately 1 g. Taking extra precautions, i.e. self-absorption
correction and deconvolution of the complex decay curves, we calculated a nitrogen concentration of 2260 ± 100 μg g−1, which is in good agreement with our GFA value of 2303 ± 64 μg g−1. The values are the second and third highest of a rather atypical (non-S-shape) distribution of data of 14 round-robin participants.
It is of utmost importance for the certification process that our IPAA value is the only one not produced by inert gas fusion
analysis and, therefore, the only one which is not affected by a possible incomplete release of nitrogen from high-melting
boron carbide.
Figure Twin-Detector system for analyzing spatially extended samples 相似文献
8.
1H MAS NMR and15N NMR studies of adsorbed N2 and N2O molecules were used to characterize Br?nsted and Lewis acidic sites of unmodified γ-Al2O3 and γ-Al2O3 modified with NaOH. Changes in the concentrations of surface hydroxyls with the increase in the number of more “basic” OH
groups for NaOH/γ-Al2O3 have been found by1H MAS NMR experiments. Two different types of Lewis acidic sites in γ-Al2O3 have been revealed using15N NMR studies. The strongest sites are poisoned even at small NaOH concentrations (ca. 0.05 wt.%). Not only the number of electron-accepting sites but also their strength are supposed to decrease for modified
γ-alumina. 相似文献
9.
Very economical, rapid and pure methods for the production of115mIn and113mIn from115Cd and113Sn, respectively are described. The methods are based on the extraction of115mIn by o-xylene from 7.2M H2SO4 −0.06M HBr, and its reextraction with ≈11M H2SO4 −0.06M HBr from n-hexane. The γ-spectra of the generated115mIn and113mIn indicate that they are free from any other interferences. 相似文献
10.
Nuclear reactions induced on light elements by low energy deuterons are investigated. Differential cross-sections for10B(d, β0)8Be,10B(d, β1)8Be,12C(d, p0)13C,14N(d, β0)12C,14N(d, β1)12C,16O(d, p0)17O,16O(d, p1)17O and16O(d, β0)14N reactions are measured between 0.5 and 3 MeV at an observation angle of 135° with respect to the incident beam. Possible
application of these reactions to the measurement of surface concentration is considered—Special emphasis was given on nitrogen
determination in order to study nitrogen concentration in industrial glasses. Surface nitrogen repartition on glass, origin
of nitrogen, influence of oxidizing and reducing conditions and glass structure are discussed. 相似文献
11.
L. G. Detsuheva M. A. Fedotov L. I. Kuznetsova A. A. Vlasov V. A. Likholobov 《Russian Chemical Bulletin》1997,46(5):874-880
Unsaturated heteropolyanions (HPA) [PW11O39]7− stabilize TiIV hydroxo complexes in aqueous solutions (Ti: PW11 [PW11O39]7−⪯12, pH 1–3). Spectral studies (optical,17O and31P NMR, and IR spectra) and studies by the differential dissolution method demonstrated that TiIV hydroxo complexes are stabilized through interactions of polynuclear TiIV hydroxo cations with heteropolyanions [PW11TiO40
5− formed. Depending on the reaction conditions, hydroxo cations Ti
n−1O
x
H
y
m+ either add to oxygen atoms of the W−O−Ti bridges of the heteropolyanions to form the complex [PW11TiO40·Ti
n−1O
x
H
y
]
k−
(at [HPA]=0.01 mol L−1) or interact with TiIV of the heteropolyanions through the terminal o atom to give the polynuclear complexes [PW11O39Ti−O−Ti
n−1O
x
H
y
]q− (at [HPA]=0.2 mol L−1). When the complexes of the first type were treated with H2O2, TiIV ions added peroxo groups.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 914–920, May, 1997. 相似文献
12.
Among a number of stable and unstable nuclides formed in material exposed to cosmic radiation the spallation nuclide53Mn (T=2·106
a) is investigated in meteoritic manganese by combined techniques of neutron activation and advanced γ-spectrometry. The need
for an economic use of precious meteorites is so ensured best. Intense neutron bombardment transforms the long-livedK-emitter53Mn into54Mn, which is detected by its 0.84 MeV γ-rays. Using the (n,γ) cross section—recently derived byMillard—53Mn-values in the range of 60–600 dpm/kg (10−11 g/g) are found in a larger number of iron meteorite samples, which are only 1–3 g in weight. The determination is very specific
and under appropriate conditions unaffected by side reactions. The attempt to use the44Ti (n,γ)45Ti reactions for the analysis of spallogenic titanium failed, because the σtherm of44Ti was found to be unexpectedly low (10 barns). Additionally,45Sc was determined after (n,γ) reaction by the46Sc γ,γ-cascades.
相似文献
13.
Using13C and1H NMR spectroscopy, titanium(IV) alkylperoxo complexes Ti(OOtBu)n(OiPr)4−n with n=1, 2, 3 and 4 were characterized in the reaction of Ti(OiPr)4 withtBuOOH in CH2Cl2 and CDCl3. 相似文献
14.
The Er3+-doped Al2O3 nanopowders have been prepared by the sol-gel method, using the aluminium isopropoxide [Al(OC3H7)3]-derived γ-AlOOH sols with addition of the erbium nitrate [Er(NO3)3·5H2O]. The five phases of γ-(Al,Er)2O3, θ-(Al,Er)2O3, α-(Al,Er)2O3, ErAlO3, and Al10Er6O24 were detected with the 0–20 mol% Er3+-doped Al2O3 nanopowders at the different sintering temperature of 600–1200°C. The average grain size was increased from about 5 to 62 nm
for phase transformation of undoped γ-Al2O3→α-Al2O3 at the sintering temperature from 600 to 1200°C. At the same sintering temperature, average grain size was decreased with
increase of the Er3+ doping concentration. Infrared absorption spectra of γ-Al2O3 and θ-Al2O3 nanopowders showed the two broad bands of 830–870 and 550–600 cm−1, the three broad bands of 830–870, 750–760, and 550–600 cm−1, respectively. The infrared absorption spectra for the α-Al2O3 nanopowder showed three characteristic bands, 640, 602, and 453 cm−1. The two characteristic bands of 669 and 418 cm−1 for Er2O3 clusters were observed for the Er3+-doped Al2O3 nanopowders when Er3+ doping concentration was increased up to 2 mol%. The 796, 788, 725, 692, 688, 669, 586, 509, 459, and 418 cm−1 are the characteristic bands of Al10Er6O24 phase. 相似文献
15.
V. V. Malyshev 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(11):1940-1945
The conductivity of semiconducting tin dioxide (SnO2) in pure nitrogen and dry air was studied over the temperature range ∼20−650°C. Conductivity was shown to be caused by chemical
transformations of oxygen molecules on catalytically active oxide surfaces. It unambiguously corresponded to the formation
of O− and O2− chemisorbed ions. The experimental data were used to construct the temperature dependences of the chemisorption of O− and O2−. The formation of O− ions was maximum at ≈200°C, and the formation of O2− ions did not reach a maximum at 650°C and increased beyond this limit. The number of electrons entrapped by chemisorbed oxygen
ions and the concentrations of oxygen ions at all formation stages were estimated. 相似文献
16.
A. Ait Haddou M. Berrada G. Paić 《Journal of Radioanalytical and Nuclear Chemistry》1986,102(1):159-175
The yield and average cross section for the reactions11B(p, n)11C,12C(p, )13N,13C(p, n)13N,
12
12
C(d, n)13N,14N(p, )11C,16O(p, )13N,16O(d, n)17F,16O(t, n)18F, and18O(p, n)18F have been measured in different compounds. The charged particles were created in the samples themselves either through recoil by scattering of 14 MeV neutrons off hydrogen and deuterium, or by the (n, t) reaction on6Li using thermal neutrons. The yields of reactions12C(d, n);16O(p, );16O(t, n) and18O(p, n) have been measured using proton, deuteron and triton spectra generated by 14 MeV neutrons in the reactions D(n, p)2n;6Li(n, d);7Li(n, d) and10B(n, d);7Li(n, t) and10B(n, t), respectively. 相似文献
17.
A. V. Levanov A. R. Gromov E. E. Antipenko V. V. Lunin 《Russian Chemical Bulletin》2000,49(4):669-673
The yields of hydrogen atoms, oxygen atoms and molecules, and hydroxyl radicals after a microwave discharge in the mixture
of CO2 and H2 were measured by ESR spectroscopy in a flow-type system. A mathematical model of the kinetics of chemical reactions downstream
the microwave discharge was devised. The concentrations of particles that cannot be detected under our experimental conditions
were estimated.
Experimental values of the concentration sensitivity for an RE-1306 ESR spectrometer are as follows: for a pressure of 1 Torr
and optimized detection conditions, H., 1011 cm−3; O., 3·1010 cm−3; OH., 1010 cm−3; O2, 3·1013 cm−3 (Ref. 7); for a pressure of 2 Torr, H., 5·1012 cm−3; O., 2·1012 cm−3; OH., 2.5·1011 cm−3; O2, 7.5·1014 cm−3 8
Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 4, pp. 665–669, April, 2000. 相似文献
18.
V. Yu. Borovkov S. P. Kolesnikov V. I. Koval’chuk J. L. d’Itri 《Russian Chemical Bulletin》2007,56(5):863-869
Adsorption of 13C18O+12C16O mixtures on the Pt(2.9%)/γ-Al2O3, (Pt(2.6%)+Cu(2.7%))/γ-Al2O3, and (Pt(2.6%)+Cu(5.1%))/γ-Al2O3 catalysts was studied by FTIR spectroscopy. On the metallic Pt surface at coverages close to saturation, CO is adsorbed both
strongly and weakly to form linear species for which the vibrational frequencies of the isolated 13C18O molecules adsorbed on Pt are ∼1940 and ∼1970 cm−1, respectively. The redistribution of intensities of the high-and low-frequency absorption bands in the spectra of adsorbed
13C18O indicates that these linear forms are present on the adjacent metal sites. The weak adsorption is responsible for the fast
isotope exchange between the gaseous CO and CO molecules adsorbed on metal. The Pt-Cu alloys, in which the electronic state
of the surface Pt atoms characteristic of monometallic Pt remains unchanged, are formed on the surface of the reduced Pt-Cu
bimetallic catalysts. The decrease in the vibrational frequencies of the isolated C=O bonds in the isolated Pt-CO complexes
suggests that the CO molecules adsorbed on the Cu atoms affect the electronic properties of Pt.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 831–836, May, 2007. 相似文献
19.
Jye-Bin Lin Jui-Ping Lee Ding-Bang Lin Wen-Kang Chen Wen-Shan Liu Chien-Yi Chen 《Journal of Radioanalytical and Nuclear Chemistry》2009,280(3):481-487
Stray neutron distribution in a medical cyclotron vault room was evaluated by neutron activation analysis (NAA). Neutrons
were generated in the production of radioactive nuclides, such as 18F, 11C, 13N and 15O, for diagnostic usage. Indium foil was adopted to evaluate the stray fast and thermal neutron intensity based on 115In(nf, n′)115mIn and 115In(nth, γ)116m1In reactions, respectively. The indium foils were weighed, sealed and placed at 62 points around the 6.7×8.2 m2 cyclotron room. Additionally, each indium foil was exposed for over 80 minutes during cyclotron operation and γ-peaks were
analyzed using an HPGe detector to evaluate the number of stray fast (Φ
f) or thermal (Φ
th) neutrons. The minimum to maximum numbers of fast and thermal neutrons were (3.47±0.11)×103 to (1.06±0.21)×104 n·cm−2·s−1 and 9 to 965 n·cm−2·s−1, respectively. The minimum detectable limit for stray neutrons was included herein to demonstrate the reliability. Accordingly,
60 and two points, respectively, the confidence level associated with the reported intensities of fast and thermal neutrons
reached 95%. The low qualified ratio in the evaluation of stray thermal neutrons might have been caused by either the high
Compton scattering plateau or the low intensity of the gamma-ray peak in the relevant spectrum. 相似文献
20.
Changlun Chen Di Xu Xiaoli Tan Xiangke Wang 《Journal of Radioanalytical and Nuclear Chemistry》2007,273(1):227-233
The fate and transport of toxic metal ions and radionuclides in the environment is generally controlled by sorption reactions.
The extent of sorption of divalent metal cations is controlled by a number of factors including cosorbing or complexing. In
this work, the effects of pH, humic acid HA/Co(II) addition orders, ionic strength, concentration of HA, and foreign cations
on the Co(II) sorption on γ-Al2O3 in the presence of HA were investigated. The sorption isotherms of Co(II) on γ-Al2O3 in the absence and presence HA were also studied and described by using S-type sorption model. The experimental results showed
that the Co(II) sorption is strongly dependent on the pH values, concentration of HA, but independent of HA/Co(II) addition
orders, ionic strength, and foreign cations in the presence of HA under our experimental conditions. The results also indicated
that HA enhanced the Co(II) sorption at low pH, but reduced the Co(II) sorption at high pH. It was hypothesized that the significantly
positive influence of HA at low pH on the Co(II) sorption on γ-Al2O3 was attributed to strong surface binding of HA on γ-Al2O3 and subsequently the formation of ternary surface complexes such as ≡S-OOC-R-(COO−)
x
Co2−x
. Chemi-complexation may be the main mechanism of the Co(II) sorption on γ-Al2O3 in the presence of HA. 相似文献