4f(1P) giant dipole resonance in La3+

Photoabsorption of free ${\mathrm{La}}^{3+}$ ions in the $4d$ excitation region has been measured using the dual-laser plasma technique. A dramatic strong and broad ${4d}^{9}4f{(}^{1}P)$ giant dipole resonance was observed. The interpretation of the results is provided using theoretical techniques which go beyond the independent particle approximation. In particular the strong term dependence for $4f{(}^{1}P)$ gives evidence of strong polarization effects for the description of the giant dipole resonance.