Consistency of ΛΛ hypernuclear events

In this work, we report on the study of Ni-doped SnO₂ nanoparticles prepared by a polymer precursor method. X-ray diffraction (XRD) data analysis evidenced the formation of only the tetragonal rutile-type phase in all samples. Meanwhile, the mean crystallite size shows a progressive reduction with the Ni content, the unit cell volume and residual strain does not show any clear dependence on the Ni content. Room temperature M?ssbauer spectra were well modeled by using two doublets which represent the particle core and shell surface regions. Assuming that the isomer shift (IS) of the core region remains constant for all samples, the isomer shift of the shell region shows a linear increase with the Ni content. That increase was assigned to the progressive increase in the s-electronic density produced by either the generation of oxygen vacancies or the formation of Ni complexes at the surface due to the surface segregation of Ni ions as the Ni content is increased. Larger QS values obtained for the doublet of the shell are associated with the stronger distortions in the nearest surrounding of tin atoms produced by the surface segregation of Ni ions.