Atomic structure calculations and beam-foil observations of La IV

Abstract

Relativistic Hartree-Fock and multiconfigurational Dirac-Fock calculations of atomic structure and transition rates have been carried out in trebly ionized lanthanum (La 3+ , Z = 57). The calculations have to cope with configuration interaction effects but also with the very complex situation of the collapse of the 4f wave function. The calculations are compared to experimental data obtained with beam-foil spectroscopy in the extreme ultraviolet, at ion energies that favour the production of the spectrum La IV. Besides lines known from sliding spark discharges, many more lines are observed that have not yet been identified. Time-resolved measurements yield three level lifetimes in La IV that agree roughly with the results of our own calculations.PACS Nos: 32.30.Jc, 32.70.Cs, 34.50.Fa, 31.15.ag, 31.15.xr Résumé : Des calculs Hartree-Fock relativistes de structures atomiques et de taux de transition et des calculs à l'aide de l'approche multiconfigurationnelle de Dirac-Fock ont été effectués dans le lanthane trois fois ionisé (La 3+ , Z = 57). Ces calculs doivent prendre en compte l'interaction de configuration mais aussi la situation très complexe associée à la contraction de l'orbitale 4f. Les calculs ont été comparés aux données expérimentales obtenues à l'aide de la spectroscopie faisceau-lame dans l'ultraviolet lointain à des énergies qui favorisent l'émission du spectre de La IV. Outre les raies spectrales connues à partir des spectres d'étincelles glissantes, beaucoup de raies supplémentaires ont été observées qui n'ont pas encore été identifiées. Les mesures résolues dans le temps ont permis d'obtenir trois durées de vie dans La IV qui sont en accord satisfaisant avec les résultats de nos calculs.[Traduit par la Rédaction]

Recent Investigations of Heavy Elements (37≤Z≤92)

“…[12]). BFS is one of the rare methods allowing the investigation of the atomic structure of moderately charged ions.…”

“…We have investigated with the BFS the spectrum emitted by the triply ionized lanthanum (La 3+ ) [12]. This work has emphasized the difficulties inherent to the investigation of the fourth spectrum of the rare-earths which could eventually be observed in some hot stars.…”

“…The available observations are however affected by large uncertainties mostly due to the lack of atomic data for the elements or ions of interest. For these reasons, HFR and MCDF calculations of atomic structure and transition rates have been carried out in trebly ionized lanthanum (La 3+ , Z = 57) [12]. Up to now, experimental data (lifetimes or transition probabilities) are available only for two elements of the group (i.e.…”

Overview of recent advances performed in the study of atomic structures and radiative processes for the lowest ionization stages of heavy elements

“…This experimental technique was used in a few cases in our work (i.e., for Xe VI-IX and La IV ions) [36][37][38][39]. The instrumental device of Liège University, Belgium, was employed for that purpose.…”

“…Indeed, up to a recent past, their radiative properties were essentially investigated from spectroscopy experiments on ions embedded in compounds or crystal lattices. Following our previous investigations of La IV [39], Ce IV [159], and Yb IV [160], we have recently extended the theoretical analysis of trebly ionized lanthanide atoms by considering the Fig. 2.…”