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Alpha decay of the new isotopes 188,189Po (1999)

Andreyev, A.N. ; Ackermann, D. ; Cagarda, P. ; [et al.]

Springer

The European physical journal 6 (1999), S. 381-385

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ISSN: 1434-601X

Keywords: PACS:23.60.+e α decay – 27.70.+q 150 ≤ A ≤ 189 – 27.80.+w 190 ≤ A ≤ 219

Source: Springer Online Journal Archives 1860-2000

Topics: Physics

Notes: Abstract. New neutron-deficient isotopes 188,189Po have been produced in the complete fusion reaction of 52Cr ions with a 142Nd target at the velocity filter SHIP. The evaporation residues were separated in-flight and subsequently identified on the basis of α-γ and α-conversion electron coincidence measurements and of α-α position and time correlations. In 189Po a ground state to ground state α decay with Eα1= 7540(20) keV, T1/2= 5(1) ms and two fine structure α-decays at Eα2= 7264(15) keV and Eα3= 7316(15) keV have been observed. In 188Po (T1/2= 400+200 −150μs) a ground state to ground state α decay at Eα= 7915(25) keV and a fine structure α decay at Eα= 7350(40) keV have been found. Improved data on the α-decay of 189Bi were obtained.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s100500050359

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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.