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Thorald Bergmann

Thorald Bergmann

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37
Publications
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1,693
Citations
Citations since 2016
0 Research Items
152 Citations
2016201720182019202020212022051015202530
2016201720182019202020212022051015202530
2016201720182019202020212022051015202530
2016201720182019202020212022051015202530

Publications

Publications (37)
Article
Magic numbers in cluster mass spectra can be caused by either geometric or electronic structure. The study of metallic compound clusters allows the number of atoms and the number of electrons in clusters to be controlled independently. We report magic numbers in the mass spectra of Cs-compound clusters and pure Na clusters containing up to 700 free...
Article
Full-text available
Polynuclear species of zirconium in acidic aqueous solution are investigated by combining X-ray absorption spectroscopy (XAFS) and nanoelectrospray mass spectrometry (ESI-MS). Species distributions are measured between pHC 0 and pHC 3 for [Zr] = 1.5–10 mM. While the monomer remains a minor species, with increasing pH the degree of polymerization in...
Article
Der faszinierende Übergangsbereich zwischen dem atomaren und dem makroskopischen Verhalten der Materie läßt sich anhand von Clustern aus einigen Atomen untersuchen.
Article
A 5.3W average output power at a pulse repetition-rate of 40kHz was achieved with a diode-end-pumped Nd:YVO4 regenerative amplifier. In a continuous-wave operation an optical efficiency of 43% was reached. The output pulse duration is 19ps, if seeded by a 7-ps-oscillator. A maximum pulse repetition-rate of 80kHz and a maximum pulse energy of 350J w...
Conference Paper
5 W average output power was achieved with a diode-end-pumped Nd:YVO<sub>4</sub> regenerative amplifier at a repetition rate of 35 kHz. A commercial 10-psoscillator was used as seed pulse source. Stable TEM<sub>00</sub> operation was obtained.
Article
5 W average output power was achieved with a diode-end-pumped Nd:YVO4 regenerative amplifier at a repetition rate of 35 kHz. A commercial 10-psoscillator was used as seed pulse source. Stable TEM00 operation was obtained.
Article
Large clusters are notoriously hard to detect. Clusters of fullerene molecules containing up to 10000 carbon atoms pose a special problem in that they tend to bounce elastically off the detector. High post acceleration and multiple charging can be used to overcome the problem of detection. Intensity anomalies in the mass spectra of (C60)n and (C70)...
Article
In order to make a qualified judgement of the ion optical properties of a time-of-flight system, it is necessary to have a method of presentation that does not require an extensive background in ion optical theory to understand it. The authors present such a method. This method gives a more clear understanding of state-of-the-art time-of-flight sys...
Chapter
In 1949 Maria Goeppert-Mayer [1] and Haxel, Jensen and Suess [2] suggested a shell model to explain magic numbers of stability for atomic nuclei. Recently, a similar model has been used to sucessfully describe another fermion system — the electrons in metallic clusters [3–18].
Chapter
In 1949 Maria Goeppert-Mayer1 and Haxel, Jensen and Suess2 suggested a shell model to explain magic numbers of stability for atomic nuclei. Recently, a similar model has been used to sucessfully describe another fermion system — the electrons in metallic clusters3–18.
Chapter
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 shel...
Article
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 shel...
Article
The properties of bulk metal are so different from those of a metal atom that it is sometimes hard to imagine how they might be related. However, a connection can be established by studying a succession of clusters containing 2, 3, 4, 5, ... atoms. If the properties of the solid were found to evolve gradually and continuously with increasing cluste...
Article
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 co...
Article
Recently observed magic number data for Na N 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 exper...
Article
Intensity anomalies (magic numbers) have been observed in the mass spectra of sodium clusters containing up to 22 000 atoms. For small clusters (Na n ,n1500) 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, indicati...
Article
Periodic patterns in the mass spectra of (Mg)n for 147 ⩽ n ⩽ 2869 indicate that these clusters have icosahedral symmetry.
Article
Magic numbers in cluster mass spectra can be caused by either geometric or electronic structure. The study of metallic compound clusters allows the number of atoms and the number of electrons in clusters to be controlled independently. We report magic numbers in the mass spectra of Cs-compound clusters containing up to 700 free electrons.
Article
Injecting neutral species at right angles to the direction of acceleration and using quadrupole ion optics allows for highest resolution and good sensitivity in time‐of‐flight mass spectrometers. We have designed such ion optics using a finite element field calculation. Imaging and timing errors have been compensated. With an acceleration voltage o...
Article
The reflector has a central influence on the properties of a time‐of‐flight mass spectrometer. The mass resolution can be greatly improved using a reflector with homogeneous fields. A reflector with homogeneous fields can also have focusing properties and thus enhance sensitivity of the instrument. In this case it is important to be aware of design...
Article
Intensity anomalies (magic numbers) have been observed in the mass spectra of sodium clusters containing up to 22000 atoms. For small clusters (Nan, 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.
Article
The investigation of shell structure in the ground states of atoms is limited to values of the angular momentum quantum number l
Article
Unusually high ionization energies have been observed for Cs–O clusters having certain sizes and composition, namely for Cs2n + zOn with z= 8, 18, 34, 58 and 92. The anomalies are well defined for clusters containing from 1 to 7 oxygen atoms. The indicated values of z are identical to the number of electrons in closed shells of angular momentum. Ma...
Article
Shell structure can be observed in the photoionization mass spectra of sodium clusters containing up to 22000 atoms, if the wavelength of the ionizing light is chosen to be just above the ionization threshold of the clusters of interest. For small cluster (Nan, n≤1500) the anomalies appear to be due to the filling of electronic shells (groups of su...
Article
Mass spectra of metal‐rich, singly and doubly ionized BanOx clusters are characterized by high peak intensities for n=13, 19, 23, 26, 29, 32, and 35 independent of the number of oxygen atoms (x=1,2,3,4). These values are identical to the magic numbers found for Ar clusters. The mass spectra of CanO show a similar behavior. Mass spectra of stoichiom...
Article
Field distortions in the vicinity of wire meshes can change the direction of passing ions. Small deflection angles of ions passing through wire meshes in the reflector can reduce the mass resolution of time‐of‐flight mass spectrometers. We calculate these effects.
Article
To perform experiments with clusters, a time‐of‐flight mass spectrometer with a mass resolution of 35 000 (m/Δm, 50% definition) has been constructed. The main design features of the instrument are presented.
Article
Photoionization spectra of CsnOx clusters have been recorded for 15≤n≤130 and 1≤x≤10. We present a method of interpreting these spectra and a computer algorithm for their evaluation. Several features of these photoionization spectra support the spherical‐jellium‐background model.
Article
Mass spectra of Naz(Na5O2)+ clusters drop sharply at z = 34, 40, 58, 92 and 138. These values are identical to the number of electrons in closed shells of angular momentum. Na138(Na5O2)+, for example, apparently has the electron configuration (1s,1p,1d,2s,1f,2p,1g,2d,1h,3s,2f,1i,3p).
Article
Unusually high ionization energies have been observed for Cs-O clusters having certain sizes and composition, namely for Cs2n+zOn with z=8, 18, 34, 58 and 92. The anomalies are well-defined for clusters containing from 1 to 7 oxygen atoms. The indicated values of z are identical to the number of electrons in closed shells of angular momentum.
Article
Unusually high ionization energies have been observed for Cs-O clusters having certain sizes and composition, namely for Cs2n+zOn with z=8, 18, 34, 58, and 92. The anomalies are well defined for clusters containing from 1 to 7 oxygen atoms. The indicated values of z are identical to the number of electrons in closed shells of angular momentum.
Article
Alcohol clusters containing varying amounts of LiI have been produced and observed in a mass spectrometer. Mass peaks corresponding to clusters of certain sizes and compositions are particularly strong. Total energy calculations have been carried out in order to determine the relative stability and structure of these clusters. From the results of c...
Article
The strong electrostatic interaction between Li+ and I- ions is screened in the presence of polar solvent molecules, eventually resulting in the dissociation of Li+-I-ion pairs. In order to better understand this-solvation process, mass spectrometry experiments and total energy calculations have been carried out on alcohol clusters containing varyi...
Chapter
An accurate description of the structural and vibrational properties of small clusters can be achieved only through a detailed examination of multi¬dimensional total energy surfaces. The importance of various properties of such a surface are illustrated for pure alcohol clusters and for alkali halide fragments dissolved in alcohol clusters.
Chapter
Although clusters are now routinely observed in mass spectrometers, their most fundamental property, their structure, is still essentially unknown /1/. This is a particularly frustrating state of affairs for the theorists, who, if given the structure, can use their sophisticated methods to calculate the electronic and vibrational properties of clus...

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