Alkali metal clusters mass spectra

The abundance spectrum of Na clusters from Knight et al. s work [4] is shown in Figure 8.1a. Sharp drops are clearly seen after A = 8, 20, 40, 58 (and 92). Later on, mass spectra of other alkali metal clusters showed similar features [5-8]. Particularly interesting is Martin et al. s [8] work, which extended the observed mass spectrum for alkali clusters up to A = 2500. Katakuse et al. measured the abundance spectra of noble metal clusters Cu, Ag, and Au, and found sharp drops after A = 3,9,21, 35, 41, 59, 93. .. [9,10]. Since alkali, Cu, Ag, and Au atoms all have one s electron each in the outermost valence shell, and experiments were performed on cationic clusters of the noble metals, drops in abundance occur at the same number of valence electrons in all these clusters. 

Example ED from untreated wire emitters in the presence of intentionally added alkali metal salts was used to obtain mass spectra of tartaric acid, arginine, pentobarbital and other compounds. [78,80] Besides [Mh-H]" quasimolecular ions, m/z 175, the FD mass spectrum of arginine exhibits [M+Na], m/z 197, and [Mh-K]", m/z 213, ions due to alkali metal cationization as well as [2M-i-H], m/z 349, cluster ions (Fig. 8.14). [37]... 

Experiments on noble metal clusters (Cun, AgN, Aun) indicate the existence of shell-effects, similar to those observed in alkali clusters. These are reflected in the mass spectrum [10] and in the variations of the ionization potential with N. The shell-closing numbers are the same as for alkali metals, that is N = 2,S,20,40, etc. Cu, Ag and Au atoms have an electronic configuration of the type nd °(n + l)s so the DFT jellium model explains the magic numbers if we assume that the s electrons (one per atom) move within the self-consistent, spherically symmetric, effective jellium potential. 

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