  The coupled states A^{1}\Sigma_{u}^{+} (^{1}D +}1}S), c^{3}\Pi_{u} (^{3}P +
^{1}S) and a^{3}\Sigma_{u}^{+} (^{3}P +}1}S) of the calcium dimer are
investigated in a laser induced fluorescence experiment combined with
high-resolution Fourier-transform spectroscopy. A global deperturbation
analysis of the observed levels, considering a model, which is complete within
the subspace of relevant neighboring states, is performed using the Fourier
Grid Hamiltonian method. We determine the potential energy curve of the
A^{1}\Sigma_{u}^{+} and c^{3}\Pi_{u} states and the strengths of the couplings
between them. The c^{3}\Pi_{u} and \as states are of particular importance for
the description of collisional processes between calcium atoms in the ground
state ^{1}S_{0} and excited state ^{3}P_{1} applied in studies for establishing
an optical frequency standard with Ca.
