Formation of positive cluster ions Li_nBr (n = 2–7) and ionization energies studied by thermal ionization mass spectrometry

Abstract

Clusters of the type Li(n)X (X = halides) can be considered as potential building blocks of cluster-assembly materials. In this work, Li(n)Br (n = 2-7) clusters were obtained by a thermal ionization source of modified design and selected by a magnetic sector mass spectrometer. Positive ions of the Li(n)Br (n = 4-7) cluster were detected for the first time. The order of ion intensities was Li(2)Br(+) > Li(4)Br(+) > Li(5)Br(+) > Li(6)Br(+) > Li(3)Br(+). The ionization energies (IEs) were measured and found to be 3.95 ± 0.20 eV for Li(2)Br, 3.92 ± 0.20 eV for Li(3)Br, 3.93 ± 0.20 eV for Li(4)Br, 4.08 ± 0.20 eV for Li(5)Br, 4.14 ± 0.20 eV for Li(6)Br and 4.19 ± 0.20 eV for Li(7)Br. All of these clusters have a much lower ionization potential than that of the lithium atom, so they belong to the superalkali class. The IEs of Li(n)Br (n = 2-4) are slightly lower than those in the corresponding small Li(n) or Li(n)H clusters, whereas the IEs of Li(n)Br are very similar to those of Li(n) or Li(n)H for n = 5 and 6. The thermal ionization source of modified design is an important means for simultaneously obtaining and measuring the IEs of Li(n)Br (n = 2-7) clusters (because their ions are hermodynamically stable with respect to the loss of lithium atoms in the gas phase) and increasingly contributes toward the development of clusters for practical applications.

Study of small chlorine‐doped potassium clusters by thermal ionization mass spectrometry

“…The present investigation of the chlorine‐doped potassium clusters is an extension of our previous studies of small halogen‐doped alkali clusters, and a continuation of our systematic study of IEs of these clusters by the thermal ionization source of modified design MS . The clusters of the type K n Cl + and K n Cl n − 1 ( n > 3) were detected for the first time simultaneously in a cluster beam generated by a potassium fluoride.…”

“…The thermal ionization source of modified design has been used in order to obtain the chlorine–doped potassium clusters and determine their IEs. Experimental details have been given elsewhere . The mass analyzer used in this research is a 12‐in radius, 90° magnetic sector.…”

Study of vaporization of LiI, LiI/C70, LiI/LiF/C70 from the Knudsen cell located into ionization chamber of the mass spectrometer

“…41 These ionization _________________________________________________________________________________________________________________________ (c) 2014 Copyright SCS energies are in agreement with the IEs obtained by theoretical calculations, meaning that the precursors of Li n I + clusters were not the same as mentioned above. units) versus temperature trends before and after the melting point of LiI (469 °C) do not correspond.…”

“…[36][37][38][39][40][41][42][43] In the earlier papers, it was shown that the experimental setup in which the Knudsen cell was located in the ionization chamber provides better conditions than the standard experimental setup of the KCMS for obtaining both the neutral and positively charged "superalkali" clusters of the type Li n X, X = F or I (n = 2, 3, 4, 5 or 6). [36][37][38][39][40][41][42][43] In the earlier papers, it was shown that the experimental setup in which the Knudsen cell was located in the ionization chamber provides better conditions than the standard experimental setup of the KCMS for obtaining both the neutral and positively charged "superalkali" clusters of the type Li n X, X = F or I (n = 2, 3, 4, 5 or 6).…”

Recent Progress on the Design, Characterization, and Application of Superalkalis

“…In the past decades, there has been increasing interest and activity in both experimental and theoretical investigations of mononuclear superalkalis, including ML 2 (M=F, Cl, Br, I; L=Li, Na, K, Cs), ML 3 (M=O, S; L=Li, Na, K), ML 4 (M=N, P; L=Li, Na), and MLi 5 (M=C, Si) . It should be mentioned that, when more alkali metal ligands are introduced, the ML k + n ( n >1) complexes– with more than one valence electron violating the octet rule can also possess lower IEs than that of alkali metal atoms. Hence, these so‐called hypervalent or hypermetalated ML k + n ( n >1) molecules also belong to the superalkali family.…”