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排序方式: 共有52条查询结果,搜索用时 15 毫秒
1.
K. D. Duch M. Heel H. Kalinowsky F. Kayser E. Klempt B. May O. Schreiber P. Weidenauer M. Ziegler D. Bailey S. Barlag J. M. Butler U. Gastaldi R. Landua C. Sabev W. Dahme F. Feld-Dahme U. Schaefer W. R. Wodrich J. C. Bizot B. Delcourt J. Jeanjean H. Nguyen E. G. Auld D. A. Axen K. L. Erdman B. Howard R. Howard B. L. White S. Ahmad M. Comyn G. M. Marshall G. Beer L. P. Robertson M. Botlo C. Laa H. Vonach C. Amsler M. Doser J. Riedlberger U. Straumann P. Truöl ASTERIX Collaboration 《Zeitschrift fur Physik C Particles and Fields》1989,45(2):223-234
Antiproton-proton annihilation at rest in a gaseous H2 target at NTP into the final state π+ π? K ± π? (K 0) with an undetectedK 0 or \(\bar K^0 \) has been investigated. We observe theE(1420) resonance in the invariant mass spectrum (K 0)miss K ± π? with massM E =1413±8 MeV/c2 and widthГ E =62 ± 16MeV/c2 and find evidence for the production of thef 1(1285). The absolute branching ratio of \(\bar p\) p → π+ π? E 0,E 0 →K 0 L K ± π ? at (61±6)%P wave annihilation is (3.0±0.9)·10?4 of all annihilations. The observed suppression of theE production fromP wave with respect to theS wave together with some simple selection rules suggest that the quantum numbers of theE(1420) areJ pc=0?+ and not I++. 相似文献
2.
C. Amsler F. H. Heinsius H. Koch B. Kopf U. Kurilla C. A. Meyer K. Peters J. Pychy M. Steinke U. Wiedner 《The European Physical Journal C - Particles and Fields》2015,75(3):124
The spin density matrix of the \(\omega \) has been determined for the reaction \({\bar{p}p}\,\rightarrow \,\omega \pi ^0\) with unpolarized in-flight data measured by the Crystal Barrel LEAR experiment at CERN. The two main decay modes of the \(\omega \) into \(\pi ^0 \gamma \) and \(\pi ^+ \pi ^- \pi ^0\) have been separately analyzed for various \({\bar{p}}\)momenta between 600 and 1940 MeV/c. The results obtained with the usual method by extracting the matrix elements via the \(\omega \) decay angular distributions and with the more sophisticated method via a full partial wave analysis are in good agreement. A strong spin alignment of the \(\omega \) is clearly visible in this energy regime and all individual spin density matrix elements exhibit an oscillatory dependence on the production angle. In addition, the largest contributing orbital angular momentum of the \({\bar{p}p~}\)system has been identified for the different beam momenta. It increases from \(L^{max}_{{\bar{p}p~}}\) \(=\) 2 at 600 MeV/c to \(L^{max}_{{\bar{p}p~}}\) \(=\) 5 at 1940 MeV/c. 相似文献
3.
Dr. Bidyut B. Sarma Jonglack Kim Jonas Amsler Dr. Giovanni Agostini Dr. Claudia Weidenthaler Norbert Pfänder Dr. Raul Arenal Dr. Patricia Concepción Dr. Philipp Plessow Prof. Dr. Felix Studt Dr. Gonzalo Prieto 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(14):5855-5864
Realizing the full potential of oxide-supported single-atom metal catalysts (SACs) is key to successfully bridge the gap between the fields of homogeneous and heterogeneous catalysis. Here we show that the one-pot combination of Ru1/CeO2 and Rh1/CeO2 SACs enables a highly selective olefin isomerization-hydrosilylation tandem process, hitherto restricted to molecular catalysts in solution. Individually, monoatomic Ru and Rh sites show a remarkable reaction specificity for olefin double-bond migration and anti-Markovnikov α-olefin hydrosilylation, respectively. First-principles DFT calculations ascribe such selectivity to differences in the binding strength of the olefin substrate to the monoatomic metal centers. The single-pot cooperation of the two SACs allows the production of terminal organosilane compounds with high regio-selectivity (>95 %) even from industrially-relevant complex mixtures of terminal and internal olefins, alongside a straightforward catalyst recycling and reuse. These results demonstrate the significance of oxide-supported single-atom metal catalysts in tandem catalytic reactions, which are central for the intensification of chemical processes. 相似文献
4.
Bidyut B. Sarma Jonglack Kim Jonas Amsler Giovanni Agostini Claudia Weidenthaler Norbert Pfnder Raul Arenal Patricia Concepcin Philipp Plessow Felix Studt Gonzalo Prieto 《Angewandte Chemie (International ed. in English)》2020,59(14):5806-5815
Realizing the full potential of oxide‐supported single‐atom metal catalysts (SACs) is key to successfully bridge the gap between the fields of homogeneous and heterogeneous catalysis. Here we show that the one‐pot combination of Ru1/CeO2 and Rh1/CeO2 SACs enables a highly selective olefin isomerization‐hydrosilylation tandem process, hitherto restricted to molecular catalysts in solution. Individually, monoatomic Ru and Rh sites show a remarkable reaction specificity for olefin double‐bond migration and anti‐Markovnikov α‐olefin hydrosilylation, respectively. First‐principles DFT calculations ascribe such selectivity to differences in the binding strength of the olefin substrate to the monoatomic metal centers. The single‐pot cooperation of the two SACs allows the production of terminal organosilane compounds with high regio‐selectivity (>95 %) even from industrially‐relevant complex mixtures of terminal and internal olefins, alongside a straightforward catalyst recycling and reuse. These results demonstrate the significance of oxide‐supported single‐atom metal catalysts in tandem catalytic reactions, which are central for the intensification of chemical processes. 相似文献
5.
C. Amsler 《Czechoslovak Journal of Physics》1994,44(4-5):309-345
Recent results in antiproton-proton annihilation at rest from the Crystal Barrel at CERN/LEAR are reviewed. Rates for annihilation at rest into various two-body channels have been measured. In spite of the complexity of the annihilation mechanism, simple tests based on the underlying quark constituents can be applied. The annihilation process is also useful to investigate the spectrum of light quark mesons and to search for exotic (non-q¯q) mesons. Three scalar states have been found in the 1500 MeV mass region. One of them is a good candidate for the ground state glueball. 相似文献
6.
7.
8.
Zurlo N Amoretti M Amsler C Bonomi G Carraro C Cesar CL Charlton M Doser M Fontana A Funakoshi R Genova P Hayano RS Jørgensen LV Kellerbauer A Lagomarsino V Landua R Rizzini EL Macrì M Madsen N Manuzio G Mitchard D Montagna P Posada LG Pruys H Regenfus C Rotondi A Testera G Van der Werf DP Variola A Venturelli L Yamazaki Y;ATHENA Collaboration 《Physical review letters》2006,97(15):153401
We present evidence showing how antiprotonic hydrogen, the quasistable antiproton (p)-proton bound system, has been synthesized following the interaction of antiprotons with the molecular ion H2+ in a nested Penning trap environment. From a careful analysis of the spatial distributions of antiproton annihilation events, evidence is presented for antiprotonic hydrogen production with sub-eV kinetic energies in states around n=70, and with low angular momenta. The slow antiprotonic hydrogen may be studied using laser spectroscopic techniques. 相似文献
9.
N. Zurlo M. Amoretti C. Amsler G. Bonomi C. Carraro C. L. Cesar M. Charlton M. Doser A. Fontana R. Funakoshi P. Genova R. S. Hayano L. V. Jørgensen A. Kellerbauer V. Lagomarsino R. Landua E. Lodi Rizzini M. Macrì N. Madsen G. Manuzio D. Mitchard P. Montagna L. G. Posada H. Pruys C. Regenfus A. Rotondi G. Testera D. P. Van der Werf A. Variola L. Venturelli Y. Yamazaki 《Hyperfine Interactions》2006,172(1-3):97-105
We descrbe how protonium, the quasi-stable antiproton-proton bound system, has been synthesized following the interaction
of antiprotons with the molecular ion in a nested Penning trap environment. From a careful analysis of the spatial distributions of antiproton annihilation events
in the ATHENA experiment, evidence is presented for protonium production with sub-eV kinetic energies in states around n = 70, with low angular momenta. This work provides a new two-body system for studies using laser spectroscopic techniques.
相似文献
10.
S. Ahmad C. Amsler R. Armenteros E.G. Auld D. Axen D. Bailey S. Barlag G.A. Beer J.C. Bizot M. Caria M. Comyn W. Dahme B. Delcourt M. Doser K.D. Duch K.L. Erdman F. Feld-Dahme M. Ziegler 《Physics letters. [Part B]》1985,157(4):333-339
K and L series X-rays have been observed from p atoms formed in hydrogen gas at NTP in association with annihilations into neutral particles. The total K X-ray yield is (6.5 ± 3.2) × 10?3 per stopped antiproton. A model-dependent fit of the K X-ray spectrum gives a Kα energy of 8.9±0.3 keV, corresponding to a strong interaction shift of (?0.5±0.3) keV. 相似文献