High resolution observations of interstellar NaI and CA II towards the Scorpio-Centaurus association

High-resolution observations (3.6 km/s FWHM) of interstellar Na I and Ca II toward 28 stars in the direction of the Sco-Cen association are presented. The observed velocity structure, velocity dispersions, column densities and Na I/Ca II ratios are discussed. Of the 58 identified velocity components (toward 23 stars), 46 (or 79 percent) were found to have negative LSR velocities. This is in agreement with previous results, and indicates a general outflow from the Sco-Cen association. By fitting an expanding shell model to the observed velocities an expansion velocity of 7 km/s was obtained. If the further assumption is made that only one component per star arises in such a shell, the best-fitting expansion velocity was found to be 9 km/s. In the latter case, the remaining components were variously identified (depending on their velocities and Na I/Ca II ratios)