Identification of cross-relaxation resonances of12B implanted in sc aluminum

Polarized¹²B nuclei were produced andrecoil implanted in single crystals of fcc aluminum. The boron decay asymmetry andrelaxation times were measured as a function of external magnetic field values andat different orientation angles of the crystal. To identify the resonances at certain field values in the¹²B depolarization in Al, a consistent theory based on the principle of a multi-spin system and Nuclear level-crossing has been developed. A unique identification of the resonances, based on the resonant interaction between boron andparticular pairs of aluminum neighbours, is perfectly possible. The strong dissipative coupling of the Al nuclei with the electron bath of the lattice hinders a straightforward interpretation of the resonance width anddepth.     

Hyperfine coupling of12B in noble metals and Al; enhancement of the conduction-electron spin susceptibility by e-e exchange

We have remeasured the Korringa contributionT _1e to the nuclear spin lattice relaxation time of the interstitial¹²B in nobel metals and in Al. TheT _1e T times the squared Knight shiftK of¹²B taken from the literature, that is the Korringa product of¹²B, shows that the conduction-electron spin susceptibility is exchange enhanced similarly to that sensed by the matrix nucleus. The enhancement factors are equal within the experimental errors for both interstitial and matrix positions in Cu and Ag. The enhancement factors at the boron and at the matrix position are different in Au and Al.     

Two magnon light scattering in K2MnF4

The light scattering spectra of the two dimensional Heisenberg antiferromagnet K₂MnF₄ are reported. At low temperatures a two magnon band is observed and four bands due to phonons as well.     

Pade-Approximants for the Electron Gas and for Symmetrical Plasmas

The range of validity for several Pade-formulae for thermodynamic functions is checked in comparison with most recently available numerical data. Landscapes of maximum deviation are plotted. Application to symmetrical electron-positron and electron-hole plasmas is performed. An evaluation of the critical data for the droplet transition in semiconductors is given.     

On the index of a holomorphic vector field tangent to a singular variety

In this article we define and compute an index for a holomorphic vector field on a (possibly singular) subvariety of a complex manifold, provided the subvariety is a local complete intersection. This index reduces to the usual Poincaré-Hopf index in case the subvariety is smooth, and is equal more generally to the index defined in [GSV] and [SS].     

EPR and luminescence of Mn2+ in MgF2 single crystals

EPR spectra of Mn²⁺ in MgF₂ crystals grown by the Bridgman technique were measured at 300 and 20 K. Application of the superposition model to the zero field splitting (ZFS) patterns indicates complete absence of dynamic contributions to the ZFS. The luminescence spectra are also in accord with substitutional incorporation of Mn²⁺.