title: Formation and ionization energies of small chlorine-doped lithium clusters by thermal ionization mass spectrometry.
abstract: BACKGROUND
  Theoretical calculations have shown that the first ionization energy of clusters of the type Li(n) Cl (n ≥2), with more than eight valent electrons, is lower than that of alkali metal atoms; hence they are named superalkali. Superalkali clusters can mimic the chemical behavior of alkali metals and may be used as building blocks of new cluster-assembled materials. There is currently no reliable experimental proof of this kind of clusters and such proof is required.
  
  
  METHODS
  The Li(n) Cl (n = 2-6) clusters were produced by a thermal ionization source of modified design, and mass selected by a magnetic-sector mass spectrometer. The modification pertains to the replacement of the side filaments by a cylinder in the triple-filament thermal ionization source. The sample, which is LiCl salt, was pressed into a ring and placed on the inner wall of the cylinder.
  
  
  RESULTS
  It was observed that the ions of clusters with an even number of lithium atoms (Li(2) Cl(+) , Li(4) Cl(+) , Li(6) Cl(+) ) are more stable than the odd-numbered ones (Li(5) Cl(+) , Li(3) Cl(+) ). The ionization energies were determined to be 3.98 ± 0.25 eV for Li(2) Cl, 4.10 ± 0.25 eV for Li(3) Cl, 3.90 ± 0.25 eV for Li(4) Cl, 4.01 ± 0.25 eV for Li(5) Cl, and 4.09 ± 0.25 eV for Li(6) Cl. The presence of a halogen atom reduces the ionization energy of the metal clusters.
  
  
  CONCLUSIONS
  The thermal ionization source of modified design presents a suitable simple way to obtaining and measuring the ionization energies of very small lithium monochloride clusters. Clusters Li(n) Cl, n = 4 to 6, were detected for the first time.
authors.affiliation: VINČA Institute of Nuclear Sciences, University of Belgrade, P.O. Box 522, 11001, Belgrade, Serbia. vsuzana@vinca.rs
authors.forename: S R
authors.initials: SR
authors.lastname: Veličković
authors.forename: J B
authors.initials: JB
authors.lastname: Djustebek
authors.forename: F M
authors.initials: FM
authors.lastname: Veljković
authors.forename: B B
authors.initials: BB
authors.lastname: Radak
authors.forename: M V
authors.initials: MV
authors.lastname: Veljković