Application of Samsonov’s configuration model in establishing the influence of the electronic structure of d-metals on thermal electron emission of WBa cathodes

DOI: 10.62564/M4-OM7404

Olena Makarenko, Iryna Podchernyaeva, Olha Hetman

Frantsevich Institute for Problems of Materials Science National Academy of Science of Ukraine


Electron emission from WBa-cathodes is carried out from an adsorbed layer of barium and oxygen atoms on W or other d-metal adsorbents. When films of the d-metals Re, Os, Ir and Ru are deposited on the emitting surface, the work function φ decreases by 0.2 eV; and in the case of Pt, Pd and Au, it increases by 0.2 eV. The aim of the work is determine the effect of the electronic structure of d-metals on the work function of the WBa cathode using the Samsonov configuration model. According to Samsonov’s configuration model, the formation of a condensed state is accompanied by the division of valence electrons into two subsystems: localized and itinerant electrons. Free-filled and half-filled configurations such as s2, s2р6, d0, d5, d10 are the most energetically stable in the spectrum of configurations.According to Samsonov’s model, oxygen atoms are electron acceptors, since they tend to fill the valence orbitals 2s22p4 with electrons in the energetically more stable state of 2s22p6. Ba atoms are electron donors, donating their 6s2 valence electrons to oxygen to form surface dipoles Ba+– O- with ionic bonds. These dipoles reduce the work function of W. Re, Os, Ir and Ru atoms have unpaired electrons in the orbitals d6 and d7, which, upon energy absorbing, transform into sp-valence states and can be electron donors, ensuring the maximum population of sp - states of oxygen. As a result, the degree of polarizability of Ba+ – O- dipoles on the surface of these adsorbents increases, which further reduces φ. Pt, Pd and Au atoms with stable d9 and d10 orbitals have a reduced donor ability and do not have the effect of reducing the work function. Сonclusion. The main mechanism of emission of WBa cathodes is the donor-acceptor interaction of adsorbed atoms among themselves and with the adsorbent, leading to the formation of polarized dipoles responsible for the escape of electrons into vacuum.

Keywords
Samsonov configuration model, WBa-cathode, work function of electron, donor-acceptor interaction

Acknowledgments
Not provided

References
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