  The laser technique of polarisation labelling of levels has been used to
study the excited 1$^1\Sigma^{+}_{\mathrm{u}}$ state of $^{88}$Sr$_2$, in most
part heavily perturbed by the neighbouring electronic states. By observation of
completely resolved rovibronic spectra we have determined positions of 2556
spectral lines originating from the labelled levels in the ground
X$^1\Sigma^{+}_{\mathrm{g}}$ state and terminating on levels of the perturbed
complex. The experimental results are confronted with the existing theoretical
predictions.
