Paris car parking problem for partially oriented discorectangles on a line

The random sequential adsorption (RSA) of identical elongated particles (discorectangles) on a line ("Paris car parking problem") was studied numerically. An off-lattice model with continuous positional and orientational degrees of freedom was considered. The possible orientations of the discorectanles were restricted between θ∈[-θ_{m};θ_{m}] while the aspect ratio (length-to-width ratio) for the discorectangles was varied within the range ɛ∈[1;100]. Additionally, the limiting case ɛ=∞ (i.e., widthless sticks) was considered. We observed that the RSA deposition for the problem under consideration was governed by the formation of rarefied holes (containing particles oriented along a line) surrounded by comparatively dense stacks (filled with almost parallel particles oriented in the vertical direction). The kinetics of the changes of the order parameter and the packing density are discussed. Partial ordering of the discorectangles significantly affected the packing density at the jamming state, φ_{j}, and shifted the cusps in the φ_{j}(ɛ) dependencies. This can be explained by the effects on the competition between the particles' orientational degrees of freedom and the excluded volume effects.