| 1. |
- Bjornstad, T., et al.
(författare)
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Study of the Giant Gamow-Teller Resonance in Nuclear Beta-Decay - the Case of Ar-32
- 1985
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Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474. ; 443:2, s. 283-301
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Tidskriftsartikel (refereegranskat)abstract
- Delayed proton and gamma emissions following the β-decay of 32Ar have been studied. The half-life of 32Ar is 98 ± 2 ms, and the T = 2 analogue state in 32Cl lies at the excitation energy 5036 ± 12 keV. From the intensity of the feeding to this state the proton intensities can be converted to an absolute scale leading to a total proton branching ratio of (43 ± 3)%. From proton-gamma coincidence measurements it emerges that (1.9 ± 0.2)% of the protons lead to the first-excited state in 31S. A level scheme up to 8.75 MeV excitation in 32Cl has been constructed and the Gamow-Teller strength function has been deduced. The result is a renormalization of the axial-vector strength to (49 ± 5)% of the free-nucleon value.
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| 2. |
- Borge, M. J. G., et al.
(författare)
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Study of the Giant Gamow-Teller Resonance in Nuclear Beta-Decay - the Case of Ar-33
- 1987
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Ingår i: Physica Scripta. - : IOP Publishing. - 1402-4896 .- 0031-8949. ; 36:2, s. 218-223
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Tidskriftsartikel (refereegranskat)abstract
- Delayed proton and gamma emissions following the beta decay of 33Ar have been studied. From the calculated intensity of the feeding to the T = 3/2 analogue state in 33C1, the proton intensities have been put on an absolute scale leading to a proton branching ratio of 38.7 ± 1.0%. A proton branch to the first excited state in 32S at 2230.2 keV (1π = 2+) with an intensity of 0.77 ± 0.10% was obtained from gamma singles and proton-gamma coincidence data. The complete spectroscopic information on 33Ar allows the Gamow-Teller (GT) strength function from the gound state and up to 9.25 MeV excitation energy in 33C1 to be deduced. The total strength observed in this interval is 2.90 in absolute units.
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| 3. |
- Andersson, Arne, et al.
(författare)
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Ammoxidation of 3-Picoline: An Activity and High-Resolution Electron Microscopic Investigation of Vanadium Oxide Catalysts
- 1986
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Ingår i: Journal of Catalysis. - 1090-2694. ; 98:1, s. 204-220
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Tidskriftsartikel (refereegranskat)abstract
- A V2O5 catalyst was used in the ammoxidation of 3-picoline to nicotinonitrile. It was observed that the selectivity for the formation of CO2 as a function of temperature passed through a minimum. This is explained to be due to the existence of weakly bonded electrophilic oxygen species at low temperatures, and an increasing degradation involving O2− at high temperatures. A comparison of two different V2O5 preparations shows the beneficial effect of the V2O5(010) plane on the formation of nicotinonitrile. The exposure of planes other than the (010) plane as the source of formation of CO2 is discussed by consideration of bond strength values. The activity, selectivity, and composition of the charged V2O5 catalyst were followed as a function of time-on-stream at various temperatures. It was found that the V2O5 phase was reduced in the course of the reaction. V4O9, VO2(B), VO2 (tetragonal), and even more reduced phases were formed depending upon the reaction temperature used. Of the pure oxides, V4O9 was found to be both less active and less selective than V2O5. VO2(B), however, is more active but less selective compared to V2O5. The phases formed were characterized by various methods including high-resolution transmission electron microscopy (HRTEM). This technique made it possible to image the View the MathML source phase boundary for the first time. The general direction of this boundary is parallel to the (301) plane of V2O5. Micrographs of VO2(B) show that the nature of defects formed depends on the reaction temperature. After use at 695 K two types of planar twin lamellae were formed. At a slightly higher temperature partly amorphous defects appeared. The influence on the catalytic reaction of the phase boundaries and defects formed is discussed.
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