H. Göhlich

Observation of electronic shells and shells of atoms in large Na clusters

Abstract Intensity anomalies (magic numbers) have been observed in the mass spectra of sodium clusters containing up to 22000 atoms. For small clusters (Na n , n ⩽ 1500) the anomalies appear to be due to the filling of electronic shells. The mass spectra of larger clusters are well explained by the completion of icosahedral or cuboctahedral shells of atoms.

Evidence for icosahedral shell structure in large magnesium clusters

Abstract Periodic patterns in the mass spectra of (Mg) n for 147 ⩽ n ⩽ 2869 indicate that these clusters have icosahedral symmetry.

Electronic shells and shells of atoms in metallic clusters

Intensity anomalies (magic numbers) have been observed in the mass spectra of sodium clusters containing up to 22 000 atoms. For small clusters (Nan,n≤1500) the anomalies appear to be due to the filling of electronic shells (groups of subshells having the same energy). The shells can be characterized rather well by a pseudoquantum-number, indicating the possible existence of a symmetry higher than spherical. The mass spectra of larger clusters (1500≤n≤22 000) are well explained by the completion of icosahedral or cuboctahedral shells of atoms. The fact that the two types of shells (electron and atom) occur in distinct and non-overlapping size intervals might indicate the existence of a “liquid” to “solid” transition in going from small to large clusters.

Observation of icosahedral shells and subshells in calcium clusters

Abstract The mass spectrum of hot calcium clusters can be characterized as a recurring set of twenty peaks. Each occurrence of the set corresponds to the formation of one icosahedral shell of atoms. Each of the twenty peaks (subshells) within a set (shell) can be correlated to the coverage of one triangular face. Groupings of five faces arranged around a common verstex play a special role in shell formation.

Fission of highly charged sodium clusters

Abstract Small, highly charged sodium clusters have been produced by multi-step ionization of large clusters followed by evaporative shrinking. The critical size, nc, beyond which Naz+n are stable obeys the approximate relation nc ≈ 8z2. However, significant deviations from constant z2/nc are clearly evident. The critical sizes for z = 2, 3, 4, 5, 6 and 7 are 27±1, 64±1, 123±2, 208±5, 321±5, and 448±10 atoms, respectively.

Ionization energies of sodium clusters containing up to 22000 atoms

Abstract Recently it has been shown that the mass spectra of sodium clusters show evidence for magic numbers up to 22000 atoms. In the present investigation we have measured the ionization potential of large sodium clusters. The results indicate that magic numbers observed earlier are caused by an increase in the ionization energy each time a geometric shell of atoms is completed.

Calculated electronic properties of medium sized sodium clusters: the inhomogeneous jellium model

Recently observed magic number data for NaN clusters in the size range from 100 to 900 atoms cannot be fully explained by density functional calculations using a homogeneous, spherical positive charge background. However, a centrally compressed spherical background yields steps in the ionization potential at just those magic numbers observed experimentally.

Shell-dependent reactivity of sodium clusters with oxygen

Abstract Variations in the reactivity of Na n for 100 ⩽ n ⩽ 800 with molecular oxygen are reported. They can be understood in terms of the recently observed large electronic shell closing effects in sodium clusters.

The Geometric Shell Structure of Metal Clusters

The mass spectrum of hot calcium clusters can be characterized as a recurring set of twenty peaks. Each occurence of the set corresponds to the formation of one complete icosahedral shell of atoms. Each of the twenty peaks (subshells) within a set (shell) can be correlated to the coverage of one triangular face. Groupings of five faces arranged around a common vertex play a special role in shell formation.

Ionization Energies of Large Sodium Clusters: Direct Evidence for Atomic Shell Structure

Recently it has been shown that the mass spectra of sodium clusters show evidence for magic numbers up to 22000 atoms. In the present investigation we have measured the ionization potential of large sodium clusters. The results indicate that magic numbers observed earlier are caused by an increase in the ionization energy each time a geometric shell of atoms is completed.