Formation, growth mechanism and packing sequences of binary alloy cluster anions from laser ablation of mixtures of lead and transition metals

Abstract

By using laser ablation of the mixtures of a transition metal (M: Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Pd, Ag) plus lead, M/Pb binary cluster anions were observed except for Zn, and the number of transition metal atoms contained in the binary clusters is at most 4. This behavior is different from that reported previously for M/Ge binary clusters. The experiments indicate that it is also very difficult to form Al/Pb clusters. The distribution patterns of M/Pb binary alloy cluster anions are remarkably similar to those of pure Pb clusters, consistent with a formation mechanism in which transition metal atoms are sequentially attached to [M(x-1)Pb(y)](-) clusters and thus form [M(x)Pb(y)](-) clusters by a simple condensation process. As the number of transition metal atoms increases, the intensities of binary clusters gradually decrease. It is proposed that [MPb(4)](-) and [MPb(5)](-) cluster anions might be the unit building blocks of M/Pb binary cluster anions, and the layer packing sequences for magic clusters are predicted on this basis. The [M(x)Pb(y)](-) binary clusters containing 13 atoms (x + y = 13; x not equal 0) are proposed to have an icosahedral structure.

Magic bimetallic cluster anions of M/Pb (M = Au, Ag and Cu) observed and analyzed by laser ablation and time‐of‐flight mass spectrometry

“…In both cases, the binary clusters containing 1, 2 and 3 coinage metal atoms were observed. Similarly to what was observed in our earlier work,17,18 Pb n − and [MPb n ] − were two dominant product series. However, the new species such as [Cu 3 Pb n ] − and [Ag m Pb n ] − (m = 2, 3) can only be distinguished using this high‐resolution mass spectrometer.…”

“…In order to compare with Cu and Ag, M/Pb (M = Cu, Ag) binary cluster anions were also analyzed using this RTOFMS. Some new species other than those observed previously18 were observed. The magic cluster species were investigated, and it was found that electron shell effects play an important role in these magic cluster species.…”

“…As for [MPb 10 ] − and [MPb 12 ] − , based on the bi‐capped square antiprism structure of Pb 10 and the icosahedron structure of Pb 13 ,12,13 the lead packing cage structures with one transition metal inside was proposed 17. However, the magic clusters observed in the [M 2 Pb n ] − and [M 3 Pb n ] − series are difficult to explain based only on this geometrical picture 18…”

“…The stability of magic cluster species of lead (containing 7, 13 and 19 atoms) has been explained assuming the closed polyhedron structures 12,13. In our earlier studies,17,18 similar structures were also used to explain the magic cluster species in M/Pb binary clusters containing one or two transition metals M (M = Co, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Pd, Ag, etc.). However, the magic cluster species present in the Pb n 2+ system (n = 9, 15, 23, 27, 35) satisfy exactly the closed electron shells criterion 16…”

On the Dynamics of Transient Plasmas Generated by Nanosecond Laser Ablation of Several Metals

“…Additionally, the area highlighted in Figure 4 d represents a secondary contribution of the positive Bi ions for wide measuring angles from 30° to 50°. The presence of metal anions in laser-produced plasmas has only been reported by the use of time-of-flight mass spectrometry measurements [ 53 , 54 , 55 , 56 ]; this is one of the first attempts to extend the LP probe technique towards understanding positive ion dynamics during the deposition process.…”