Photoelectron spectroscopy of cold aluminum cluster anions: Comparison with density functional theory results

Abstract

Photoelectron spectra of cold aluminum cluster anions Al(n)(-) have been measured in the size range n=13-75 and are compared to the results of density functional theory calculations. Good agreement between the measured spectra and the calculated density of states is obtained for most sizes, which gives strong evidence that the correct structures have been found. In particular the results confirm the occurrence of rather different structural motifs in this size range, from fcc-like stacks over fragments of decahedrons to disordered structures. An analysis of the density of states of representatives of the different structural motifs shows that the electronic structure is strongly influenced by the cluster geometry, and that a clear jelliumlike electron shell structure is present only in some exceptional cases.

A multi-agent quantum Monte Carlo model for charge transport: Application to organic field-effect transistors

“…[41][42][43][44][45][46][47][48][49][50][51][52][53][54][55] Issendorff and coworkers have also coupled a cryogenic 12-pole linear ion trap with a magnetic-bottle PES analyzer for the study of atomic clusters. 114 The moderate resolution of the magneticbottle analyzer is sufficient for MCAs, for which no slow electrons are possible due to the RCB. However, for singly charged anions, the cryogenic Paul trap offers an opportunity to conduct high-resolution PES using PE imaging.…”

Spectroscopy of metal “superatom” nanoclusters and high-Tcsuperconducting pairing

“…However, we found that for just a few sizes (Al 37,44,66,68 ) with decreasing temperature there appears a bulge-like feature close to the ionization threshold. The clearest and most prominent example is observed in the photoionization spectrum of the closed-shell [9,10,[46][47][48] "magic" cluster Al 66 with 198 valence electrons, as seen in the progression of spectra shown in Fig. 3(b) [43].…”

“…Taking, therefore, for an estimate λ b ≈2 together with the Al 66 intershell spacing of δ≈0.3-0.35 eV (deduced from photoelectron spectroscopy data [10,48] as the distance between the half-maximum points on the facing slopes of the topmost peaks), so that ξ in Eq. (2) is ≈0.15-0.17 eV (since μ is located halfway between the highest-occupied and lowest-unoccupied shells [13]), and a characteristic vibrational frequency ~35 meV, it is found that the equation for T c yields a solution of ≈70 K [64].…”

“…For nanocluster sizes which do not possess a filled spherically symmetric electronic shell, the state degeneracy is lower, but the chemical potential μ becomes positioned at the highest occupied electronic levels (as opposed to lying halfway up to the next unoccupied shell as in the closed-shell "magic" cluster discussed above) and the level spacing also decreases because of the geometrical distortion of the cluster [48]. The first effect works against pairing but the last two make it more favorable, hence high T c may occur in open-shell clusters as well.…”

“…Among the possibilities are Al, Zn, Cd, Ga and In. We chose to work with aluminum because it is a well-known superconductor (crystalline T c =1.2 K, amorphous T c =6 K [44]) and at the same time many Al n clusters with n>40 are well described by the shell model [9,10,[45][46][47][48]. In addition, the metal is essentially isotopically pure 27 Al which eliminates any complications with mass spectrometric identification of cluster sizes.…”