V. 0. MARTIROSYAN et al. : ESR of the %Ions in a Trigonal Field 44 1 phys. stat. sol. (b) 72, 441 (1975) Subject classification: 19; 13.4; 22.8.1 Erevan State University (a) and V . I . Vernadskii Institute of Geochemical and Analytical Chemistry, Academy of Sciences of the USSR, Moscow (k) ESR of the %-Ions in a Trigonal Field: Fe3+ in a-LiI03 BY V. 0. MARTIROSYAN (a), M. L. MEILMAN (b), I. N. MAROV (b)l), V. V. ZHUKOV (b), and K. T. SEVINYAN (a) The ESR spectra of Fe3+ impurity ions localized in positions of trigonal symmetry in a-LiIO, single crystals are investigated in the X-and &-bands at room temperature. The parameters of spin-Hamiltonian are: g,, = g!1 = 2.0014; g,, = gg2 = g 1 = 2.0080; b.2 = = 7.831 GHz; b i = -0.133 GHz; b: I= -0.101 GHz. In X-band the temperature dependence of the spectra in the interval (-180 to + 180 "C) is studied. Possible models of active centres in cc-LiIO, crystals are discussed. The results show that a preferable substitution scheme in the investigated crystals is Fez+ ---f Li+. A close connection is obtained between the fine structure parameters of the ESR spectra of iron group ions in crystals of lithium iodate, niobate, and tantalate. Es werden die ESR-Spektren von Storstellen der Fe3+-Ionen auf Platzen mit trigonaler Symmetrie in a-LiJ0,-Einkristallen im Xund &-Band bei Zimmertemperatur untersucht. Folgende Parameter des Spin-Hamiltonoperators wurden bestimmt : g, = gil = 2,0014; gll = gg2 = gL = 2.0080; b! = 7,831 GHz; b i = -0,133 GHz; bi = -0,101 GHz. Fur das X-Band wurde die Temperaturabhkngigkeit der Spektren im Bereich von -180 bis 180 "C untersucht. Mogliche Modelle der aktiven Zentren in den a-LiJ0,-Kristallen werden diskutiert. Die Ergebnisse zeigen, daB in den untersuchten Kristallen die Substitution Fez+ --Li+ bevorzugt ist. Es wird eine enge Verkniipfung erhalten zwischen den Feinstrukturparametern der ESR-Spektren der Ionen der Eisengruppe in den Kristallen von Lithiumjodat, -niobat und -tantalat.

Doubly differential 8-electron emission cross sections A2~(E,,6,)/AE,AflZ, have been measured as a function of the electron energy E, and the electron emission angle 6, for the collision systems 1.4 MeV U-' U33+ on neon and argon. The angular distributions of the emission cross sections show a maximum at 6, = 60", in agreement with parameter-free n-body classical-trajectory Monte Carlo ( ~-C T M C ) calculations. The cross sections show an extreme anisotropy between forward and backward emission compared with those of light-ion data. The cross sections decrease exponentially for 6,2 90". The n -c T M c calculations indicate that the large projectile Coulomb force highly polarises the target-atom electrons in the two-centre field. A large fraction of the ionised electrons are emitted into an angular region of 6, = 60" opposite to the recoiling target ion. The two-centre potential is crucial for the description of such clustered emission of S electrons.

No abstract

No abstract

No abstract