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The states 1^1Σ^+_u, 1^1Π_u and 2^1Σ^+_u of Sr_2 studied by Fourier-transform spectroscopy

A high resolution study of the electronic states 1^1Σ^+_u and 1^1Π_u which belong to the asymptote 4^1D + 5^1S and of the state 2(A)^1Σ^+_u, which correlates to the asymptote 5^1P + 5^1S, is performed by Fourier-transform spectroscopy of fluorescence progressions induced by single frequency laser excitation. Precise descriptions of the potentials up to 2000 cm^{-1} above the bottom are derived and compared to currently available ab initio calculations. Especially for the state 1^1Σ^+_u large deviations are found. Rather weak and local perturbations are observed for the states 1^1Π_u and 2^1Σ^+_u, while a strong coupling of the state 1^1Σ^+_u to the component Ω=0^+_u of the state 1^3Π_u, which belongs to the asymptote 5^3P + 5^1S, is indicated.