Laser photodetachment electron spectroscopy studies of heavy atomic anions

Abstract

Laser photodetachment electron spectroscopy (LPES) experiments have been performed at the Negative Ion Research Facility at the University of Nevada, Reno, using a crossed ion-laser beams apparatus to investigate the structure and dynamics of heavy atomic anions. A small ion accelerator is used to produce monoenergetic beams of negatively-charged atomic ions. Ejected electrons (photoelectrons), produced by the collision of the ions with linearly-polarized photons, are collected and their kinetic energy is measured with a hemispherical-sector electrostatic analyzer. The resultant photoelectron spectrum is used to determine the electron affinity (EA) of several of the lanthanides, while limits on the electron affinities for others are inferred. In addition, the angular asymmetry parameters and angular distribution patterns of photoelectrons created by laser photodetachment of several heavy atomic anions, as well as the spectral dependence of those angular distributions, have been determined. Electron affinities and photoelectron angular distribution asymmetry parameters can offer crucial information regarding the electronic structures of these heavy atomic anions, and represent key information for models of these complex systems.

Linear quantum capacitance scaling for lanthanide and actinide atoms: Analysis of two differing sets of electron-affinity predictions

“…Also, using the A values of O'Malley and Beck, capacitance scaling for f -filling lanthanide atoms follows the pattern observed in p-filling first and second row neutral atoms. Further, work by investigators [17][18][19] other than O'Malley and Beck favors the 6p electron attachments that occur in their lanthanide electron affinity calculations and that appear to be instrumental in producing the single capacitance scaling line seen in Fig. 1.…”

“…If all those anion attachments did not occur in such a simple manner, in the same orbital, the resulting capacitance scaling might not occur on a single line. There is some independent evidence from experiments [17,18] and from theory [19], however, that electron attachments to produce lanthanide anions in their ground states do take place in 6p orbitals. This argues further in favor of capacitance scaling along a single line, like that in Fig.…”

Conundrum in Measured Electron Affinities of Complex Heavy Atoms

“…Measured EAs for atomic Eu [1,4], Tb [17], Tm [18], Nd [17] and Nb [6,9] are available and, except for Nb, have been compared with other data in [2]. It is noted that ref.…”

Negative Ion Binding Energies in Complex Heavy Systems

“…(1) In [2] it was concluded that both the measured and the calculated EAs for the lanthanide atoms Eu [4][5][6][7][8], Tb [9,10], Tm [11,12], Gd [5,10] and Nd [5,6,9], including the Nb [13][14][15][16] atom require reinterpretation. New recommended EA values for these atoms were presented.…”