High-resolution studies on laser-induced collisional-energy-transfer profiles

High-resolution spectra of laser-induced collisional energy transfer between europium and strontium are obtained for collisional interactions which are dipole-dipole in nature. A universal profile is found for this laser-induced excitation. For the first time a precise comparison with available calculations is possible. The line core agrees well with a theory assuming a dipole-dipole coupling, but the quasistatic wing deviates from the asymptotic behavior expected for a pure dipole-dipole interaction.