Compilation, Calculation and Validation Of Fundamental Data for Diatomic Molecules Ursel Fantz and Dirk Wünderlich Max-Planck-Institut für Plasmaphysik, EURATOM Association, Boltzmannstr. 2, 85748 Garching, Germany The compilation of atomic and molecular data for plasma edge modelling is focussed on atomic and molecular hydrogen (and its isotopomeres) and on hydrocarbon species, i.e. CH and C2 molecules. Franck-Condon factors and transition probabilities are calculated with the code TraDiMo on the basis of potential curves and dipole transition moments compiled from literature. The already available data set for transitions in hydrogen molecules has been extended by calculating transitions from the hydrogen molecule to the ground state of the molecular hydrogen ion. Vibrationally resolved cross sections and rate coefficients for electron impact collisions are compiled from literature and, if not available, calculated using the code IPProg, which is based on the Impact Parameter method. Data sets for CH and C2 will be presented, which are also the basis for collisional radiative modelling using the flexible code Yacora. The analysis of populating and depopulating processes allows for an assessment of their relevance in plasma edge, e.g. calculations of photon emissivity coefficients. In order to address the importance of heavy particle collisions in dissociation modelling of hydrocarbons, Yacora calculations with and without taking into account heavy particle collisions will be shown. Calculated population densities and particle densities are validated by dedicated experiments in laboratory plasmas and in the plasma edge of fusion experiments.