N2H+ and N2D+ in interstellar molecular clouds. II- Observations

Abstract

We present observations of the $J$=1--0, 2--1, and 3--2 rotational transitions of N$_2$H$^+$ and N$_2$D$^+$ towards a sample of prototypical dark clouds. The data have been interpreted using non--local radiative transfer models.Comment: 12 pages, 18 figure