[en] The present work investigates the 4 ²P impact excitation of potassium by longitudinally polarized electrons. Exchange scattering causes a polarization transfer from the primary electron beam to the ensemble of excited atoms which results in a non zero circular polarization of the fluorescence light emitted in foreward direction. The experimental values of light polarization agree well with values calculated using close coupling data of Moores. (orig.)

[en] The hyperfine structure (HFS) of the four high lying, metastable atomic states 3d⁴ 4s ²H_9/2,11/2 and 3d³ 4s²²D_3/2,5/2 of V-51 have been measured. The measurements are carried out using the ABMR-LIRF method (atomic beam magnetic resonance, detected by laser induced resonance fluorescence). The magnetic dipole and the electric quadrupole interaction constants A, B have been obtained from these measurements. (orig.)

[en] In (ns-np)-excitation of alkali atoms by polarized electrons some of the spin orientation of the primary electron beam is transferred to the excited atoms because of exchange collisions. In the present work the polarization transfer to Na, K, Rb, and Cs respectively is studied by looking for the circular light polarization transfer of (np-ns)-decay radiation emitted in forward direction following impact excitation by a beam of longitudinally polarized electrons. Maximum polarization transfers are observed at collision energies with values about 1.5 times that of np-thresholds. The transfer increases with increasing atomic number. In case of (6s-6p)-excitation of cesium 45% of primary electron spin polarization is transferred to the atoms at maximum. The agreement with available close coupling data is statisfactory. (orig.)

[en] Since 1990 our Institute has been conducting Be-7 measurements in the atmosphere in order to use it as a tracer for air coming from the upper layers of the atmosphere and for stratospheric ozone. In this paper we present the results on Be-7 and ozone concentrations obtained with a one year monitoring campaign carried out in Sondrio, an alpine town in Northern Italy. For a few interesting events, correlation between beryllium and ozone is observed. Be-7 reveals itself as a good marker which reaches ground level during particularly rare events, such as stratospheric intrusions. (Author)

[en] A new imaging technique is presented, based on the detection of Compton scattering photons and a further statistical analysis of the collected data. The photon detection has been performed by the Enhanced Compton Spectrometer (ECoSp) a recently devised instrument that allows one to collect the backscattered photons by investigating the tested sample from one side only. Photons collected during the planar scanning of a given area are used to describe the electronic density of the sample as a density image; afterwards, the Principal Component Analysis (PCA) was applied to the image. As a case study, a non-destructive testing of plaster substrates supporting mural paintings has been performed using this technique, searching for flaws, defects, fractures and so on. The rationale behind this procedure is that the presence of such gaps, into the otherwise uniform material, can be revealed because the existing correlation between the backscattering radiation detected by ECoSp from each adjacent volume of interest (VOI) during the scanning. The principal component correlation analysis, performed over the resulting data from all VOIs, then reveals each gap in his size, shape and position

[en] The hyperfine structure (HFS) of the four high lying and metastable fine structure levels of vanadium-51 have been calculated. The calculations are based on the parametrization of one- and two-body interactions to the second order perturbation theory for a model space of the three configurations 3d^3+M4s^M (M=0,1,2). The experimental HFS data were measured using the laser spectroscopic double-resonance technique (ABMR-LIRF) with high-frequency precision. (orig.)