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1.
Charged particle spectrometry was used to determine the isotopic concentration of lithium in lithium fluoride targets irradiated
with a deuteron beam of 4.0 MeV. Alpha particles emitted by the6Li(d, α)4He and7Li(d, α)5He reactions were used as a measure of6Li and7Li, respectively. From the6Li/7Li α-count ratio the isotopic concentration of6Li was determined for isotopic concentrations over the range 7.42 (natural) to about 30 atom%6Li, with a relative standard deviation of±4.1%. Alpha particles from the19F(d, α)17O reaction could also be measured as an internal standard, extending the measurements from natural to 100 atom%6Li and giving a relative standard deviation of ±1.9%. The effect of target thickness on the accuracy of the determinations
was investigated. 相似文献
2.
K. Müller R. Henkelmann J. P. Biersack P. Mertens 《Journal of Radioanalytical and Nuclear Chemistry》1977,38(1-2):9-17
The isotopes3He,6Li,7Be and10B exhibit extremely large cross sections, between 1 and 48 kilobarn, for (n, p) or (n, α) reactions with thermal neutrons.
Together with now available extracted thermal neutron fluxes of 10( n·cm−2·sec−1 or more, these reactions present a highly sensitive method of detecting the mentioned light elements in any heavy matrix
material. Through the experimentally determined energy losses of the emitted protons or α-particles, also well resolved depth
profiles can be obtained, as demonstrated here for some relevant examples from semiconductor and fusion technology. 相似文献
3.
The non-destructive determination of lithium was performed by using a Cerenkov counter for the detection of the 13 MeV (max)
β-particles from the 0.84 sec8Li produced by the reaction7Li(n,γ)8Li. Under optimal conditions for a favorable signal-to-noise ratio, a count rate of about 35 cps/μg lithium at the beginning
of the measurement was obtained, with a background of 4.5 cps and a working range of 3–400 μg lithium. The interference of
other elements was studied. Several lithium-containing minerals and a sample of Dead Sea water were analyzed. The isotopic
composition of lithium in aqueous solutions was determined by the simultaneous measurement of the neutrons produced by the
reactions6Li(n,α)t and18O(t,α)17N, and the β-particles emitted by8Li. 相似文献
4.
J. F. Singleton N. E. W. Hartley 《Journal of Radioanalytical and Nuclear Chemistry》1979,48(1-2):317-325
A scanned microbeam has been used to profile tapered corrosion sections of thickness up to 500 μm. The method of beam scanning
and data collection is described and selected profiles are presented for the reactions D(3He, p)α,12C(d, p)13C,14N(p, α)12C and18O(p, α)15N. Finally the advantages and limitations of the technique are discussed. 相似文献
5.
Three different proton-induced reactions were used to analyze 19 pure lithium compounds of known composition. Prompt alpha-particles were measured from the reaction7Li(p, )4He at Ep=4.5 MeV and prompt gamma-rays of 429 and 479 keV from the ractions7Li(p,n)7Be and7Li(p,p)7Li, respectively, at Ep=4.5 MeV. Elemental stopping powers were calculated from tables and used to compute the stopping power of the target matrices by Bragg's Law. Apparent discrepancies in the measured yield could point to deviations from Bragg's Law and hence to molecular effects. The maximum value for any molecular effect was found to be <5.5%. 相似文献
6.
I. Golicheff M. Loeuillet Ch. Engelmann 《Journal of Radioanalytical and Nuclear Chemistry》1974,22(1-2):113-129
The experimental device used is described. Excitation functions are given for an angle of observation 150° with respect to
the incident beam. The possibilities of applying these reactions to the measurement of surface lithium and fluorine concentrations
are considered. The detection limits for these two elements are shown to be 5·10−3 μg·cm−2 with protons of energy between 1,350 and 1,500 keV. The method is compared with that based on the detection of prompt γ-rays
from the reactions7Li(p, γ)8Be and19F(p, α γ)16O.
相似文献
7.
Experimental data are presented for comparison of the determination of oxygen by the16O(3He, p)18F,16O(3He, α)15O and18O(p, α)15N prompt nuclear reactions, and of their use in the lattice location, by the ion-channelling technique, of oxygen atoms in
single crystal targets of elements such as niobium, where oxygen contents of ≈0.1 atomic % or more can be obtained. Both reaction
cross-sections and lattice-defect production rates are considered in the comparison. Details are given of an arrangement for
automatic crystallographic angular scanning of nuclear reaction and backscattering yields in channelling/lattice location
measurements. 相似文献
8.
Determination of isotopic composition of lithium by neutron activation analysis; comparison with mass spectrometry 总被引:1,自引:0,他引:1
An activation analysis method is described for routine determination of6Li-abundances in various lithium compounds on the basis of the reaction sequence6Li(n,α)T and16O(t, n)18F and the measurement of18F. Irradiations of diluted equeous solutions of samples containing CrO3 as internal flux monitor were carried out at a thermal neutron flux density of ϕ≤1011 n·cm−2·sec−1. Interferences from variations in neutron self-shielding oxygen concentration and triton range do not exceed 0.5% when using
the dilution technique. The results for6Li abundances from 3.52 to 7.60% with standard deviations of 1 to 2.5% were confirmed by mass spectrometric measurements. 相似文献
9.
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
10.
Y. Duval M. Thellier C. Heurteaux J. C. Wissocq 《Journal of Radioanalytical and Nuclear Chemistry》1980,55(2):297-306
The unidirectional influx of borate has been studied inLemna minor plants with the aid of purified boron isotopes,10B and11B. Isotope10B was detected specifically by nuclear reaction10B(n, α)7Li in the presence of “homogeneous” detectors. Despite technical difficulties in performing the10B-estimations in the plant samples themselves, the results obtained here were consistent with those of efflux experiments,
published previously, where the10B-measurements were performed in the external solution. Kinetic parameters of borate transports inLemna minor have been calculated. 相似文献
11.
S. Shibata Y. Takashima R. Gensho M. Honda 《Journal of Radioanalytical and Nuclear Chemistry》1977,36(1):11-18
The nuclide53Mn was produced by the following three nuclear reactions,52Cr(d, n)53Mn,51V(3He n)53Mn and50Cr(α, n), (α, p)53Mn. Enriched52Cr and50Cr metal targets were prepared on copper plate holder by electrodeposition. The commercially available natural vanadium foil
was used for the51V(3He, n)53Mn reaction. Each target was bombarded in a cyclotron. Manganese was extracted and purified without using carrier from the
bombarded targets by anion and cation exchanges and solvent extraction. The isotopic ratio53Mn/55Mn was measured by mass spectrometry and the amount of55Mn was determined by neutron activation analysis. The activity of53Mn obtained was 7 dpm by 750 millicoulombs in3He bombardment (E3He=20 MeV). The activity due to by-product54Mn was about several thousands times higher than that of53Mn in3He and deuteron bombardments, which were produced through51V(3He, γ)54Mn and53Cr(d, n)54Mn. In alpha bombardment (Eα=15 MeV), the activity of53Mn produced was 8 dpm by 95 millicoulombs. The activity ratio, dpm54Mn/dpm53Mn, was about 3, and this ratio was the best one among the results so far obtained. 相似文献
12.
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
13.
14.
H. Yonezawa T. Shigematsu K. Kudo 《Journal of Radioanalytical and Nuclear Chemistry》1982,68(1-2):135-143
Oxygen in silicon was determined by the secondary nuclear reactions of6Li(n, α)T and16O(t, n)18F. Lithium fluoride was deposited in vacuum on fused quartz, covered with the sample and irradiated in a nuclear reactor.
The depth profiles of18F in fused quartz and in silicon were observed, and enough depth to eliminate surface oxygen was estimated. On the basis of
these results, oxygen was determined by the average cross-section method. Oxygen concentration in CZ silicon with various
growing condition was 5–26 ppm and was consistent with those determined by the infrared absorption method. The detection limit
of oxygen in silicon is 5 ppm. 相似文献
15.
Nuclear data needs for fusion reactor design are briefly outlined. A summary is given of the radiochemical methods like precipitation,
co-precipitation, liquid-liquid extraction, ion-exchange and high-pressure liquid chromatography which have been applied in
the determination of cross-section data for (n, p), (n, n' p), (n, α), (n, n′p), (n, α), (n, n′ α), (n, t) and (n3He) reactions at 14 MeV, especially on potential wall materials and transmuted species. The measured data are discussed briefly.
A radiochemical method is described for the experimental determination of space dependent tritium production rate in a lithium
model blanket. Tritium was separated from Li by vacuum extraction and was determined quantitatively by gas phase β−-counting. A comparison of the experimental and computational results is given. 相似文献
16.
234U/238U α-activity ratios determined by α-spectrometry (AS) and those calculated from the atom ratio data using the half-life values
are compared in some of the isotopic reference materials of uranium and a few other uranium samples. For α-spectrometry, electrodeposited
sources were prepared and a large area passivated ion implanted (IPE) detector (450 mm2) was used for recording the α-spectra. The isotopic composition of U was determined by thermal ionisation mass spectrometry
(TIMS) and the recommended half-life values of234U and238U were used to calculate the α-activity ratio. It is observed that234U/238U α-activity ratios calculated from the atom ratio data are consistently high, with a mean difference of about 5%, when compared
to the α-spectrometry results. This discrepancy warrants confirmation by a few more laboratories and suggests redetermination
of the half-life values of234U and238U. 相似文献
17.
G. Dreibus B. Spettel H. Wänke 《Journal of Radioanalytical and Nuclear Chemistry》1977,38(1-2):391-403
With a newly developed method fluorine and the other halogens have been measured in terrestrial, meteoritic and lunar samples.
As a valuable byproduct lithium was determined also via teh reactions6Li (n,α)t→16O (t, n)18F. From our measurements the following new values for the “cosmic” abundance are derived (in atoms per 106 Si atoms) F 750, Cl 4350, Br 8.83, and I 1.14. We could show that the Li/Be or Li/Zr ratios can be used to estimate the ratio
of the Mg-silicates to the group of refractory elements and in course to calculate the bulk composition of the Moon and other
planetary objects. 相似文献
18.
V. I. Grishkovets 《Chemistry of Natural Compounds》1999,35(5):547-551
Chromatographically inseparable mixtures of oleanolic and ursolic 3-O-α-L-rhamnopyranosyl-(1→2)-O-α-L-arabinopyranosides (glycosides
B1 and B2) and their 28-O-α-L-rhamnopyranosyl-(1→4)-O-β-D-glucopyranosyl-(1→6)-O-β-D-glucopyranosyl esters (glycosides F1 and F2) are isolated from the leaves ofTupidanthus calyptratus Hook f. (Araliaceae). The structures of the isolated glycosides are established from chemical methods and1H and13C NMR spectra. Glycoside F2 is a new triterpene glycoside.
Simferopol' State University. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 627–633, September–October, 1999. 相似文献
19.
W. W. Osterhage 《Journal of Radioanalytical and Nuclear Chemistry》1980,56(1-2):267-275
A compilation of the cross sections (n, p), (n, n′ p), (n, α) (n, n′ α) and (n,3He) for93Nb,92,95,96,97,98,100Mo by 14 MeV neutrons is presented in the form of a table containing the results of nearly 70 different measurements, mainly
obtained by activation analysis. Brief assessments of the experimental methods and the data status are given. 相似文献
20.
J. R. Mcginley L. Žikovský E. A. Schweikert 《Journal of Radioanalytical and Nuclear Chemistry》1977,37(1):275-283
The use of heavy ion activation as a method for the analysis of hydrogen and deuterium has been evaluated. Thick target yields
from reactions of7Li,10B,11B and19F on1H and2H have been determined; activation curves for many of these reactions are presented and interferences are evaluated. Hydrogen
has been determined in titanium via1H(10B, α)7Be at the 100 and 33 ppm levels with relative precisions of 8 to 10%. 相似文献