No abstract

Monocrystals and powders of some binuclear Cu(I1) carboxilates which EPR spectra cannot be described by the usual S = 1 spin Hamiltonian were investigated. It is shown that all the peculiarities of their spectra can be interpreted taking temperature dependent intermolecular exchange into account. The observed effects are discussed assuming that the triplet exciton is able to migrate through the crystal lattice.Einkristalle und Pulver einiger binuklearer Cu(I1)-Carboxilate werden untersucht, deren EPR-Spektren mit dem gewohnlichen S = 1 Spinhamiltonoperator nicht beschrieben werden konnen. Es wird gezeigt, daB alle Besonderheiten ihrer Spektren mit der Annahme einer temperaturabhingigen, intermolekularen Austauschwechselwirkung erkliirt werden konnen. Die beobachteten Effekte werden mit der Annahme eines durch das Kristallgitter wandernden Triplett-Exzitons diskutiert.The presence of an exchange interaction between copper atoms in Cu(I1) carboxilates allows to consider such compounds as binuclear ones whose molecules are constructed similarly to the copper acetate monohydrate [l]. Their general formula can be written as (RCOO),Cu, -2 L. The exchange interaction between copper atoms in binuclear molecules gives rise to the formation of a ground singlet state with S = 0 and an excited triplet state with S = 1, which is responsible for the paramagnetism of dimeric Cu(1I) carboxilates. I n this case the following spin Hamiltonian can be used for the interpretation of the EPR spectra:

The fast luminescence, the transient absorption spectra, and the recombination kinetics are observed and investigated in a-Al,O,. Absorption spectra reveal short-lived bands at 2.75 and 2.15 eV. Their decay times remain the same (30 to 200 ns) in the temperature interval 80 to 293 K. They are found to be almost the same as the lifetime of the fast components of the luminescence band at 3.8 eV. They are expected to be due to interstitial aluminium ions. Experimental results argue for subthreshold creation of short-lived Frenkel defect pairs in the cation sublattice of a-Al,O,. Die schnelle Lumineszenz und die Ubergangs-Absorptionsspektren sowie die Rekombinationskinetik in a-Al,O, werden untersucht. Die Absorptionsspektren zeigen Bander mit kurzer Lebensdauer bei 2,75 und 2,15 eV. Ihre Abklingzeiten bleiben im Temperaturintervall von 80 bis 293 K die gleichen (30 bis 200ns) und stimmen annahernd mit der Lebensdauer der schnellen Komponente des Lumineszenzbandes bei 3,8 eV uberein. Sie werden Zwischengitter-Al-Ionen zugeschrieben. Die Experimente sprechen fur die unterschwellige Bildung von Frenkel-Defekt-Paaren kurzer Lebensdauer im Kationenuntergitter des a-Al,O,.

No abstract

HBrO4, which is obtained from NaBrO4 by a known procedure, is neutralized by NH4OH or by RbOH to yield NH4BrO4 (space group Pnma, Z=4) and the novel compound RbBrO4 (space group Pnma or Pn2,a, Z=4).