  Precise potentials for the ground state X1Sigma+g and the minimum region of
the excited state 2_1Sigma+u of Sr2 are derived by high resolution
Fourier-transform spectroscopy of fluorescence progressions from single
frequency laser excitation of Sr2 produced in a heat pipe at 950 Celsius. A
change of the rotational assignment by four units compared to an earlier work
(G. Gerber, R. M\"oller, and H. Schneider, J. Chem. Phys. 81, 1538 (1984)) is
needed for a consistent description leading to a significant shift of the
potentials towards longer inter atomic distances. The huge amount of ground
state data derived for the three different isotopomers 88Sr2, 86Sr88Sr and
87Sr88Sr (almost 60% of all excisting bound rovibrational ground state levels
for the isotopomer 88Sr2) fixes this assignment undoubtedly. The presented
ground state potential is derived from the observed transitions for the radial
region from 4 to 11 A (9 cm-1 below the asymptote) and is extended to the longe
range region by the use of theoretical dispersion coefficients together with
already available photoassociation data. New estimations of the scattering
lengths for the complete set of isotopic combinations are derived by mass
scaling with the derived potential. The data set for the excited state
2_1Sigma+u was sufficient to derive a potential energy curve around the
minimum.
