Il Nuovo Cimento (1911-1923)

In this paper a thermodynamical treatment of nuclear polarization in paramagnetic solids is developed. The general validity of the results obtained byA. W. Overhauser for alkali metals, is confirmed. We find that it is possible to achieve a degree of nuclear polarization equal to the one obtainable with the same magnetic field and temperature for electrons.

Si descrive un metodo di spettrofotometria fotografica con sorgente ausiliaria basato sull’uso di una fenditura a V,secondo il quale è possibile desumere i rapporti di intensità direttamente dai rilievi microfotometrici, senza passare attraverso la curva caratteri’stica. Si mostrano i vantaggi che presenta in generale l’uso delle fenditure a Ve si suggeriscono alcuni perfezionamenti relativi alla pratica spettrofotometrica consueta.

The scanning methods for the photographic emulsions, used in the study of the pion-proton elastic scattering, are discussed. A particular method is described, which is useful in the research of the backwards scatterings (135° <θ c.m. ⩽ 180°). It has been employed in order to detect some eventual contribution of waves withl > 1, by analysing the behaviour of dσ/dΩ in this angular interval. The analysis of dσ/dΩ for the scattering process π+ + p at 120 MeV, based on 871 events, shows that no wave withl > 1 is present in a measurable quantity. The phase-shifts of theS andP waves result: $$\alpha _3 = - 10.3 \pm 2.9; \alpha _{33} = 31.8 \pm 1.6; \alpha _{31} = - 2.6 \pm 1.6.$$