Predicted abundances of different molecules in gas phase (top row), ice surfaces (middle row), and ice mantles (bottom row) of TMC 1 (left column), and Barnard 1b (right column), according to the different desorption schemes. They are plotted as a function of the number density, together with the visual extinction that corresponds to such densities (see Figs. 4a and b, 5a and b), and the time according to a freefall collapse.