In this thesis accurate predictions for the spectroscopic parameters of l-C3H+ and C4 are made
from state-of-the-art electronic structure calculations. Both molecules are of interest to
interstellar cloud chemistry and only scarce experimental information about their rovibrational
properties is available. Christopher J. Stein recapitulates the basics of the computational
methods applied and gives an in-depth description of the computer program developed for the
rovibrational calculations.
