On the 1${}^1{\mathrm{\Sigma }}_{\mathrm{u}}^{+}$ electronic state in strontium dimer

The laser technique of polarisation labelling of levels has been used to study the excited 1${}^1{\mathrm{\Sigma }}_{\mathrm{u}}^{+}$ 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${}^1{\mathrm{\Sigma }}_{\mathrm{g}}^{+}$ state and terminating on levels of the perturbed complex. The experimental results are confronted with the existing theoretical predictions.