Electronic Energy Levels in the Trivalent Lanthanide Aquo Ions. I. Pr3+, Nd3+, Pm3+, Sm3+, Dy3+, Ho3+, Er3+, and Tm3+

TLDR

The study examines how electrostatic, spin–orbit, and configuration‑interaction parameters vary across the lanthanide series. Free‑ion energy‑level schemes for Pr³⁺, Nd³⁺, Pm³⁺, Sm³⁺, Dy³⁺, Ho³⁺, Er³⁺, and Tm³⁺ aquo ions were determined from absorption spectra in dilute acid at 25 °C, with assignments made by comparing to crystal spectra and correlating calculated and observed band intensities. Several transitions were identified for most ions, producing bands up to 45 000–50 000 cm⁻¹, and the number of assignments justified including configuration‑interaction effects in the energy‑level calculations.

Abstract

The free-ion energy-level schemes of the Pr3+, Nd3+, Pm3+, Sm3+, Dy3+, Ho3+, Er3+, and Tm3+ aquo ions have been determined from their absorption spectra in dilute acid solution at 25°. Energy-level assignments were made by comparison with crystal spectra, and on the basis of correlations between calculated and observed band intensities. For most of the ions, it was possible to identify several transitions giving rise to bands at energies as high as 45 000–50 000 cm−1. Sufficient numbers of assignments were made to justify inclusion of the effects of configuration interaction in the calculation of the energy-level parameters. Variation of the electrostatic, spin–orbit coupling, and configuration-interaction parameters across the lanthanide series is examined.