In this thesis I present the results of photoassociation measurements in ensembles ofatomic calcium over an intensity range of below 1 W/cm2 up to 600 W/cm2. The temperatureof the atoms was reduced to 1 μK by laser and evaporative cooling. Afterwardsthe two most-weakly bound states in the excited molecular potentials that dissociateto the asymtote 3P1+1S0 have been investigated regarding the shape and absolute rateof the resonances. The investigation showed that the measured rates differ by morethan an order of magnitude compared to theoretical calculations. The predictions arebased on a scattering formalism by Bohn & Julienne and wave functions derived fromcoupled-channel calculations. The shape of the resonances, the width in particular,agrees well with the numerical calculations. Especially the power broadening at highintensity is reproduced by the experiment. Further the light shift introduced by thephotoassociation laser has been measured which also differs from the predictions.In the further course of the thesis the numerical simulations were improved by consideringadditional influences like the exact dependence of the Franck-Condon density andthe light shift of the photoassociation laser as a function of the collision energy. Additionallythe modeling of the experimental setup with a special emphasis on the volumeof the optical trap and thus the density of the atomic ensemble was improved and theinfluence of varying trap depth and photoassociation duration has been studied. Investigatingpossible explanations for the discrepancy of the measured rates compared totheory, I show that by a modification of the coupling parameter and the spontaneousdecay rate of the molecular state the rates measured in the experiment can be reproducedtheoretically, with the restriction that at high intensity the calculated line shapeno longer agrees with the measurement. In the last chapter an improved experimentalapparatus is presented that by using an optical lattice suppresses thermal broadeningand thus simplifies the analysis substantially.