RESUMEN
Hyperfine parameters and the pressure dependence of the magnetic transition temperatures of FeRhGe2have been investigated. Sample has been prepared using high pressure-high temperature synthesis technique. FeRhGe2consists of two B20 structure phases with close lattice constants. The phase separation stays constant in the temperature range 4-300 K. The magnetic transition temperaturesTc1= 213 K andTc2= 135 K of FeRhGe2slightly increases with pressure in the range 0-4.5 GPa. We have compared this pressure dependence with some others compounds in the family Fe1-xRhxGe. The two phases in FeRhGe2have slightly different values of the hyperfine magnetic fields.
RESUMEN
The interaction of positronium (Ps) with molecular oxygen dissolved in liquids is experimentally investigated. Computer software has been developed for fitting the positron annihilation lifetime spectra in liquids using parameters with clear physical meaning: rate constants of the Ps chemical reactions, annihilation rate constants of the different positron states, probability of Ps formation in a quasi-free state, typical formation time of a Ps nanobubble. Such processing of the spectra allowed identification of the dominant interaction of the Ps atom with dissolved oxygen. It turns out to be mainly ortho-para-conversion (Ps â 1/4 p-Ps + 3/4 o-Ps), but not oxidation (Ps + O2â e+ + O2-). Values of the reaction rate constants are obtained.
