Electronic Structures and Related Properties. Electron Impact Ionization Potentials of Gold and Silver Clusters Me_n, n ≤ 22

Abstract

Small noble metal clusters were produced by a gas aggregation technique and were investigated mass spectrometrically using electron ionizing energies ranging from 100 eV down to the threshold region. For energies above approximately 20 eV electronic effects are displayed, that characterize a stable cationic distribution, i.e. enhanced stability is found for odd numbered clusters posessing an even number of electrons, furthermore, shell closing appears at n = 3, 9, 21… On the other hand, the electronic effects found while investigating the threshold energy region have to be attributed to neutral clusters, i.e. even numbered clusters are more stable.–The vertical ionization potentials in this region clearly demonstrate the manifestations of shell effects as well as distinct even‐odd oscillations. For both Ag and Au a dramatical drop in the ionization potential is observed from dimer to trimer. The overall size‐dependence of the ionization energies differs from that of alkali clusters due to the presence of d‐electrons.

An investigation of enhanced secondary ion emission under Aun+ (n=1–7) bombardment

“…From our calculations, the ionization potential and electron affinity obtained for the gold atom are 9.58 eV and 2.31 eV, respectively, in good agreementÅ withÅ theÅ experimentalÅ valuesÅ ofÅ 9.23Å eVÅ [44,45]Å andÅ 2.31Å eVÅ [45].Å ForÅ theÅ goldÅ dimer,Å theÅ calculated ionization potential, binding energy, bond length, and frequency were 9.59 eV, 2.12 eV, 2.55 Å, and 170 cm Ϫ1 , respectively. This compares well with the experimentallyÅ determinedÅ valuesÅ ofÅ 9.50Å eVÅ [44],Å 2.35Å eVÅ [45],Å 2.47 ÅÅ [45],Å andÅ 191Å cm Ϫ1Å [45].…”

Far-IR Spectra of Small Neutral Gold Clusters in the Gas Phase

“…The mass spectrum contains no signals for this cluster size, neither for the bare cluster, nor for its krypton complexes. This can be attributed to the very high ionization potential of this cluster, which is measured to be 8.8 eV [29] and thus well above the photon energy used here for ionization (7.8 eV). The predicted ground state structure is a planar triangle (D3h, 1 E').…”

“…From n = 9 on, all bare gold clusters and the Kr complexes are efficiently ionized. For the bare clusters, this follows largely the known experimental vertical ionization energies that had been determined via threshold electron impact ionization [29]. The Kr complexes are expected to have a lower ionization energy (IE) compared to the bare clusters by approximately the strength of the charge-induced dipole interaction in the cationic AunKr + complex [55].…”

“…There are only few direct experimental studies on neutral gold clusters in the gas phase. Their ionization potentials have been determined by threshold electron impact ionization [29], excited states of Au3 have been characterized via resonant two-photon ionization spectroscopy [30], and for the same size, a vibronic spectrum in the mid-IR has been measured in a Ne matrix [31]. Optical spectra of odd-sized clusters Aun (n = 7, 9, 11, 13) have been measured using photodissociation of weakly bound complexes with Xe atoms [32] as well as for mass-selectively deposited small (n = 1-5, 7-9) Au clusters in Ne matrices [33].…”

Structures, Stabilities, Reactivities, and (Hyper)Polarizabilities of Small Gold Clusters

“…Among the metal clusters, there is an increasing interest [20][21][22][23][24][25][26][27][28][29][30][31][32] in the noble metals (Cu, Ag, and Au) because they can be considered as a connection between the alkali metals and the transition metals. We recall that their electronic configurations are nd 10 (n + 1)s 1 , with n = 3, 4, and 5, respectively to Cu, Ag and Au.…”