Clusters of Divalent Elements: Electronic Properties of Cd_x‐Aggregates

Abstract

We have recently succeeded in generating and detecting neutral cadmium clusters Cd, (x < 80) in a seeded supersonic molecular beam. The mass spectrometric abundances of photoionized clusters exhibit remarkable intensity variations. There are large intensity ratios for Cdlo/Cdll as well as Cd20/Cd21 indicating the closing of electronic shells with 20 and 40 electrons. The photoelectron spectra of neutral cadmium clusters show the formation and filling of shells, indeed. Discrete electronic states (2s') have been observed directly in the photoelectron spectra of mass specified Cdlo clusters. Pronounced electronic shell closings are also clearly observed for clusters with 70 electrons (Cd33, 92 electrons (Cd4&. and 138 electrons (Cd,,). Furthermore, we have obtained quantitative information on the size dependence of ionization potentials and photoionization cross sections. The ionization potentials (7.7 f 0.1 eV for the dimer Cd2 and 5.0 f 0.1 eV for Cd&) decrease rapidly but rather smoothly with increasing cluster size.

Ionization potentials and charge localization in small charged group 12 clusters

“…The clusters built up with the 12 group elements (Hg, Cd and Zn) have drawn attention to the nature of the chemical bonding. As the cluster size is increasing, a transition from van der Waals interaction to covalent and finally metallic behavior has been predicted and studied experimentally for mercury [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] and for cadmium [12,19,20]. Numerous amount of theoretical works [21][22][23][24][25][26][27][28][29][30] have been devoted to reveal the phase transitions in mercury clusters.…”

“…The evolution of surface plasmon absorption has been observed with respect to the cluster size [5,6]. Nevertheless the measurement of the ionization potential by either photoionization [11,12] or electron-impact ionization mass spectroscopy [3,7] was the main technique to assess the transition of the chemical bond in neutral mercury clusters.…”

The importance of being tetrahedral: the cadmium pyramids CdN; N = 4, 10, 20, 35 and 56

“…For the divalent Group-12 elements Zn and Cd, with two valence electrons per atom, anomalously strong abundance peaks are found for clusters of 6,10,18,20,28,30,32,35,40,41,46,54,57, 60 and 69 atoms. 4,5 The peaks for Cd N with N ¼ 10, 20 and 35 are very pronounced. While other than tetrahedral magic numbers occur, we here study the question whether the systems with the tetrahedral magic numbers are actually tetrahedral.…”

Spodium bonding with noble gas atoms

“…Ionization potentials (IPs), photoelectron spectra and mass spectrometric abundance have all been established by previous experimental investigations on Cd clusters. [10][11][12] These experiments have seen the significance of electronic shell structures and a quick switch from van der Waals to metallic behaviour. An empirical tight-binding computation has been used to theoretically describe the IPs of Cd n clusters up to 55 atoms.…”