Theoretical analysis of ionic autoionization spectra of lanthanum via an intermediate state [Xe]5d6d 1P1

In the framework of multi-channel quantum defect theory, eigenquantum defects μ_α and the transformation matrices U_iα of La⁺ are calculated from first principles by relativistic multi-channel theory, while the dipole matrix elements D_α are obtained by fitting with experimental data. Then the ionic autoionization spectra of lanthanum via the intermediate state Xe]5d6d ¹P₁ in the energy region of 90213--91905~cm^-1 are obtained. Experimental peaks are classified and assigned by comparing with the corresponding calculated spectra. More specifically, four ionic autoionization Rydberg series converging to La²⁺ 5d_5/2²D_5/2 and several states converging to higher lying states of La²⁺ are found and assigned.