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In-beam γ-spectroscopy with relativistic radioactive ion beams (1999)

Wan, S. ; Gerl, J. ; Cub, J. ; [et al.]

Springer

The European physical journal 6 (1999), S. 167-174

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ISSN: 1434-601X

Keywords: PACS: 25.60.+v reactions induced by unstable nuclei – 25.75.+r relativistic heavy ion collisions – 23.20.Lv gamma transitions and level energies – 27.40.+z 39 〈 A 〈 58 – 29.30.Kv X- and γ-ray spectroscopy

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract: This work demonstrates the feasibility of in-beam γ-spectroscopy employing radioactive ion beam species at relativistic energies of E = 210 ∼ 280 A· MeV. Neutron-rich nuclei below 48Ca with neutron number between the two magic numbers 20 and 28 have been investigated. Using a Pb target, single step inelastic excitation originating mainly from Coulomb interaction takes place populating preferentially low-lying low-spin states and enabling the extraction of B(E2) values. On a C target, nucleon removal reactions are dominating and medium-spin states are populated thus offering spectroscopic information in neighboring nuclei. Cross sections of inelastic excitation are determined and compared to coupled-channels calculations. Two new states of the very neutron-rich nucleus 44Ar at 1.78(8) MeV and 2.61(16) MeV are deduced from γ-transitions.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s100500050331

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Photochemische Reaktionen. 71. Mitteilung. Die Photoisomerisierung eines spirocyclischen α, β-EpoxyketonsEin Teil der Resultate wurde bereits in Vortragsreferaten erwähnt [2]. (1973)

Wüthrich, H. J. ; Siewinski, A. ; Schaffner, H. ; [et al.]

New York, NY : Wiley-Blackwell

Helvetica Chimica Acta 56 (1973), S. 239-258

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ISSN: 0018-019X

Keywords: Chemistry ; Organic Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: On direct UV. irradiation and on triplet sensitization with acetophenone the spirocyclic epoxyketone (R)-(-)-9 undergoes racemization (Φ313/334 0.014, ΦSens 0.0060) and rearrangement to the enantiomeric spiro-β-diketones (R)-(+)-14 (Φ313/334 0.068, ΦSens 0.0037) and (S)-(-)-14 (Φ313/334 0.024, ΦSens 0.0023). The quantum yield data show that triplet reaction due to intersystem crossing is unimportant on direct irradiation, and they exclude that one common diradical intermediate of type d (Scheme 8) for the three reaction paths is involved in both the singlet and the triplet reaction. The postulate of photolytic Cα—O epoxide cleavage to intermediates of type d for the rearrangement requires that the rate of rearrangement is greater than the rate of rotation around the Cα—Cβ; bond in a given d, and that the rate difference is greater in singlet-generated d than in the triplet analogue. Reclosure of diradicals d and/or photolytic Cα—Cβ cleavage to diradical e and reclosure can account for the racemization of 9.The optically active spiro-β-diketone 14 was found to racemize also on direct irradiation and on triplet sensitization. Furthermore, both 14 and the isomeric β-diketone 20, which was obtained by UV. irradiation of the homocyclic epoxyketone 19, photochemically isomerize to the enol lactones 23 and 21, respectively.

Additional Material: 3 Ill.