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  • Articles  (28)
  • 36.40.+d  (28)
  • Springer  (28)
  • American Institute of Physics
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  • 1995-1999  (8)
  • 1990-1994  (20)
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  • 1995  (8)
  • 1992  (20)
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  • Physics  (28)
  • Geosciences
  • 1
    Electronic Resource
    Electronic Resource
    Static and dynamical distortions of helium clusters (1995)
    Springer
    The European physical journal 98 (1995), S. 421-428 
    Details
    ISSN: 1434-6036
    Keywords: 36.40.+d ; 33.70.Jg ; 67.40.Yv
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We examine the effects of impurities (“doping”) and rotational excitation on the structural and energetic properties of helium clusters. Quantum Monte Carlo (QMC) techniques are used to study ground and rotationally excited states of pure and doped clusters. We use exponentially correlated wave functions and treat the molecular impurities as rigid. Whereas pure HeN show essentially monotonic decay of density from a central maximum value, addition of impurities induces local ordering of He to an extent dependent on the impurity-He binding. Rotational excitation of HeN gives rise to extremely large centrifugal distortions. The location of impurities also appears to change upon rotational excitation. The implications of these distortions on impurity spectra are discussed for SF6HeN, and compared to recent experimental results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01338418
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  • 2
    Electronic Resource
    Electronic Resource
    CARS diagnostics of a CO2-laser pyrolytic experiment for the production of nanosized ceramic powders (1995)
    Springer
    Applied physics 61 (1995), S. 367-375 
    Details
    ISSN: 1432-0649
    Keywords: 36.40.+d ; 42.65.Dr
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Spatial distributions of rotational temperatures and molecular number densities of C2H2 and H2 were measured with CARS during the production of ultrafine SiC powders in a laser pyrolytic process flame. By means of a CO2 laser, the reaction gases SiH4 and C2H2 (or alternatively C2H4) are converted into SiC and H2. From the CARS measurements temperature gradients are determined between 8.8 × 105 K/m and 1.6 × 106 K/m with corresponding heating rates of 1.8 × 106 K/s and 1.3 × 106 K/s. The CARS data also allow an estimation of the gas expansion behaviour in the reaction zone. Moreover, they show that diffusive velocity components of the hydrogen in the hot reaction zone do not exceed 0.4 m/s.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01081537
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  • 3
    Electronic Resource
    Electronic Resource
    The dimer sputtering mechanism of Cu(001) at low bombarding energy (1992)
    Springer
    Applied physics 55 (1992), S. 364-371 
    Details
    ISSN: 1432-0630
    Keywords: 79.20.N ; 36.40.+d
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The emission of dimers during bombardment of a Cu(001) surface by Cu atoms of 300 and 1000eV energy is studied. A molecular dynamics simulation method based on many-body potentials is employed. At 300eV bombarding energy, around 81% of the sputtered dimers originate from second-nearest neighbor sites. 58% of these are ejected in a collision sequence correlated by the projectile. These dimers lead to a second maximum in the kinetic energy distribution of emitted dimers at around 8eV, besides a maximum at 4eV. Only the latter is found at 1000eV bombarding energy. As in this case mostly next-neighbor surface atoms are sputtered, the specific emission mechanism found at 300eV is irrelevant. Finally, we show that the direction of the angular momentum of sputtered dimers is correlated with the original surface site of the dimers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00324086
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  • 4
    Electronic Resource
    Electronic Resource
    Calculation of the dispersion of the third-order optical nonlinearity in C60 films (1995)
    Springer
    Applied physics 60 (1995), S. 49-55 
    Details
    ISSN: 1432-0630
    Keywords: 42.65.An ; 36.40.+d ; 31.20.Sy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Using wave functions determined from ground-state local-density calculations, we have calculated the wave-dispersed free response of the optical nonlinear polarizabilityγ (3)(−3ω;ω,ω,ω), for the C60 molecule andχ (3)(−3ω;ω,ω,ω) i.e. Third-Harmonic Generation (THG) for films using a sum-over-states approach. The influence of screening was determined by applying an external static electric field in separate selfconsistent calculations to evaluate induced dipole moments which was used to determine the static linear and nonlinear polarizabilities. The polarizabilities calculated in the static limit were used to determine an effective screening parameter which was, in turn, used together with an RPA approach to calculate screened wave-dispersed, third-order nonlinear optical properties such asγ (3)(−3ω;ω,ω,ω) andχ (3)(−3ω;ω,ω,ω). Comparing evaluated polarizabilities with experimental values we found that the non-resonant free polarizability compares well in absolute magnitude with experimental results. Inclusion of screening results in a polarizability about two orders of magnitude below the experimental values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01577612
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  • 5
    Electronic Resource
    Electronic Resource
    Pairing effects in metal clusters (1992)
    Springer
    The European physical journal 22 (1992), S. 659-666 
    Details
    ISSN: 1434-6079
    Keywords: 74.20.Fg ; 36.40.+d
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Motivated by the experimental finding of oddeven alternations in the mass spectra and ionization potentials of metal clusters, we have investigated the possibility of interpreting these results as evidence for pairing correlations among the electrons. For the present exploratory calculations, we have used a spherical BCS model which we have applied, as an example, to some Al clusters. Additional model calculations have been carried out for Na N with 34〈N〈100 in order to illustrate a possible systematics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01426369
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  • 6
    Electronic Resource
    Electronic Resource
    Production and properties of CO2 cluster anions (1992)
    Springer
    The European physical journal 24 (1992), S. 289-296 
    Details
    ISSN: 1434-6079
    Keywords: 36.40.+d ; 35.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Stoichiometric and non-stoichiometric negatively charged CO2 cluster ions have been produced in a crossed neutral cluster/electron beam ion source. The abundance and stability of these ions have been studied with a double focussing sector field mass spectrometer. The observed abundance anomalies (“magic numbers”) in the mass spectra of (CO2) n − and (CO2) n O− ions correlate with corresponding small and large metastable fractions of these ions (for loss of one CO2 unit). Variation of the measured metastable fractions as a function ofn are related to corresponding changes in the monomer binding energies. In addition, we have observed for the first time (CO2) n O 2 − ions (i.e. at electron energies above 8 eV with an energy resonance at about 14 eV) and we discuss possible production mechanisms for these ions. Relative electron attachment cross sections have been determined in the energy regime O〈E≦20 eV for (CO2) n − , (CO2) n O− and (CO2) n O 2 − withn=1 to 20. The shape of the cross section function for (CO2) n O− is strongly dependent on the cluster sizen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01425751
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  • 7
    Electronic Resource
    Electronic Resource
    Cluster size effects (1992)
    Springer
    The European physical journal 24 (1992), S. 247-275 
    Details
    ISSN: 1434-6079
    Keywords: 36.40.+d ; 31.20.Ej ; 35.20-i ; 33.80.-b
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In this paper we address some of the unique, novel and basic features of clusters, which involve the physical and chemical consequences of their large surface/volume ratio and the size dependence of the properties of large finite systems. Energetic, quantum, electronic, spectroscopic, and electrodynamic size effects in clusters were quantified by cluster size equations (CSEs), which describe the gradual “transition” from the large finite cluster to the infinite bulk system, with increasing the cluster size. Some progress was also accomplished in the description of the “transition” from cluster microsurfaces to macrosurfaces, which can be described in terms of surface CSEs. The analysis implies a nonuniversality principle for cluster size effects, with different physical properties being described in terms of distinct CSEs. The CSEs provide a quantitative answer to a central question in the area of cluster chemical physics: What is the minimal cluster size for which its properties become size invariant and do not differ in any significant way from those of the macroscopic sample of the same material? A unified (but not universal) description is advanced for the merging between the properties of microscopic large finite systems and those of a macroscopic bulk material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01425749
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  • 8
    Electronic Resource
    Electronic Resource
    On the electrostatic energy of charged alkali clusters (1992)
    Springer
    The European physical journal 23 (1992), S. 269-274 
    Details
    ISSN: 1434-6079
    Keywords: 36.40.+d
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In the framework of the jellium model an algorithm is presented to calculate the electrostatic energy of charged metal clusters of arbitrary shape. Explicit expressions are given for some special shapes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01437404
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  • 9
    Electronic Resource
    Electronic Resource
    Molecular dynamics of 300 keV (D2O)100 clusters on Ti-D (1992)
    Springer
    The European physical journal 24 (1992), S. 385-394 
    Details
    ISSN: 1434-6079
    Keywords: 36.40.+d ; 52.20.Hv ; 79.20.Nc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We use the molecular dynamics code DAMSEL to predict the velocity distributions for beam and lattice atoms after bombardment of Ti-D “foils” of thickness 20.86 Å by 300 keV (D2O)100 cluster ions. From these distributions we estimate the D-D nuclear fusion yield. We find that cluster bombardment reduces the overall energy deposition of the beam in the lattice compared to that of the individual beam atoms of the same velocity. However, a small portion of lattice atoms (〈1%), and a larger percentage of beam atoms (∼30%), have energies above the maximum present in the case of bombardment by individual D or O atoms. The folding of the standard D-D fusion cross sections over the relative velocity distributions produced by beam and lattice deuterons produce a fusion yield estimate of ∼1×10−21 fusions per cluster, with the high-energy distributions of beam deuterons playing the most important role. This is nine orders of magnitude lower that the data of Beuhler et al. While transient (∼10 fs) atom densities 50% higher than that of the initial lattice are recorded in the course of the simulation, the average energy transferred per lattice atom — 23 eV — is insufficient to support any “collision spike” explanation of the observed fusion yield.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01426688
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  • 10
    Electronic Resource
    Electronic Resource
    Collision induced fragmentation of mass-selected (CO2) n + clusters (1992)
    Springer
    The European physical journal 22 (1992), S. 521-527 
    Details
    ISSN: 1434-6079
    Keywords: 36.40.+d ; 34.90.+q
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The collisional velocity dependence of the cross sections for fragmentation of mass-selected (CO2) n + (n+2...7) clusters in collisions with Ar atoms is presented. Interesting structure can be observed in the cross sections which indicate that the collision occurs between the Ar atom and one CO2 molecule within the cluster. The results may be explained by assuming that the collision leads to either vibrational excitation of a loosely bound CO2 monomer which then leaves the cluster or excitation of the entire cluster to a dissociative state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01426094
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  • 11
    Electronic Resource
    Electronic Resource
    Electronic structure calculations of small Al n (n=2–8) clusters (1992)
    Springer
    The European physical journal 22 (1992), S. 641-644 
    Details
    ISSN: 1434-6079
    Keywords: 31.20.Ej ; 36.40.+d
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The electronic states of small Al n (n=2–8) clusters have been calculated with a relativistic ab-initio MO-LCAO Dirac-Fock-Slater method using numerical atomic DFS wave-functions. The excitation energies were obtained from a ground state calculation of neutral clusters, and in addition from negative clusters charged by half an electron in order to account for part of the relaxation. These energies are compared with experimental photo-electron spectra.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01426366
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  • 12
    Electronic Resource
    Electronic Resource
    Helium cluster ions RgHe x + (Rg=Ne, Ar and Kr,x≦14) formed in a drift tube cooled by liquid helium (1992)
    Springer
    The European physical journal 22 (1992), S. 645-650 
    Details
    ISSN: 1434-6079
    Keywords: 36.40.+d ; 35.20.Wg
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Rare gas ions Ne+, Ar+ and Kr+ are injected into a drift tube which is filled with helium gas and cooled by liquid helium. Helium cluster ions RgHe x + (Rg=Ne, Ar and Kr,x≦14) are observed as products. Information regarding the stability of RgHe x + is obtained from drift field dependence of the size distribution of the clusters, and magic numbers are determined. The magic numbers arex=11 and 13 for NeHe x + andx=12 for ArHe x + and KrHe x + . NeHe x + , Ar+ and Kr+ are proposed as the core ions for NeHe 13 + , ArHe 12 + and KrHe 12 + , respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01426367
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  • 13
    Electronic Resource
    Electronic Resource
    Ab-initio study of localization of an excess electron in sodium halide clusters (1992)
    Springer
    The European physical journal 23 (1992), S. 91-98 
    Details
    ISSN: 1434-6079
    Keywords: 31.20.Di ; 31.20.Ej ; 31.90.+s ; 36.40.+d
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The equilibrium geometries of Na n F n and Na n F n−1 are optimized forn=2, 3, 4 at the SCF level. The Na n F n molecules appear as formed by Na+ and F− ions. The paper studies the localization of the excess electron in the Na n F n−1 molecules. Na n F n−1 is obtained by removing from Na n F n a fluorine atom, and the excess electron takes the place of this lacking center, and allows a weak bond between the neighbouring Na atoms. Secondary minimum geometries, for which the excess electron has no defined place, are also studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01436708
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  • 14
    Electronic Resource
    Electronic Resource
    Ab initio calculation of the vertical excitation energies of small helium cluster ions (1992)
    Springer
    The European physical journal 22 (1992), S. 741-745 
    Details
    ISSN: 1434-6079
    Keywords: 31.20.Tz ; 33.20.Lg ; 36.40.+d
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Quantum chemical ab initio calculations have been performed for the vertical excitation energies and oscillator strengths of all low-lying electronically excited states of small helium cluster ions, He n + ,n=2, ..., 7. The geometrical structures of the ions were fixed at the equilibrium geometries of the respective ground states, for He 4 + and He 5 + also one alternative structure was considered. The low-lying excited states can be classified into two categories: the electronic transition can occur either within the central He 2 + or He 3 + unit or from the peripheral weakly bound He atoms to this unit. The latter transitions are very weak (f≈0.001), closely spaced, with vertical excitation energies of about 5.7 eV. The He 2 + and He 3 + units have strong transitions at 9.93 and 5.55 eV, respectively; these transitions are only slightly blue-shifted if He 2 + or He 3 + are placed as “chromophores” into the centre of a larger He n + cluster. The large difference in the vertical excitation energy of the strong transition should enable an experimental decision of the question whether the cluster ions have He 2 + or He 3 + cores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01437257
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  • 15
    Electronic Resource
    Electronic Resource
    Effects of surface roughness on the electronic structure of metallic clusters (1992)
    Springer
    The European physical journal 24 (1992), S. 57-63 
    Details
    ISSN: 1434-6079
    Keywords: 36.40.+d ; 31.20.Pv ; 05.40.+j
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We study the electronic level density in spherical clusters. Due to the granularity of the ionic background the surface is irregular at the microscopical level. We show that this affects the shell structure and that the level statistics display from the bottom to the top of the spectrum a transition from a poissonian behaviour to one consistent with the predictions of random matrices theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01436604
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  • 16
    Electronic Resource
    Electronic Resource
    Infrared molecular beam depletion spectroscopy of size-selected methanol clusters (1992)
    Springer
    The European physical journal 24 (1992), S. 277-287 
    Details
    ISSN: 1434-6079
    Keywords: 36.40.+d ; 33.20.Ea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Molecular beam depletion spectroscopy has been employed to study the dissociation of small methanol clusters in the spectral region between 1000 and 1100 cm−1 which covers thev 8 CO stretch (1033.5 cm−1) and thev 7 CH3 rock (1074.5 cm−1) monomer vibrations. Size selection has been achieved by dispersing the (CH3OH) n cluster beam by a secondary He beam. Aside from the recently published CH3OH dimer absorption bands at 1026.5 and 1051.6 cm−1 which are assigned to the excitation of the CO stretching vibrations in the non-equivalent subunits of the hydrogen-bonded complex, a previously unobserved band was found at 1071.3 cm−1. This absorption band is attributed to the excitation of the CH3 rocking vibration in the dimer. It appears that this transition which is very weak in the free methanol monomer receives substantial oscillator strength due to the intermolecular interaction in the complex. A splitting of this band could not be observed. The trimer and tetramer spectra feature single peaks for the CO stretching vibration being centered at 1042.2 cm−1 and 1044.0 cm−1, respectively. This observation is consistent with the cyclic structures of these species. The trimer and tetramer rocking vibrations are observed near 1060.5 cm−1 but cannot be localized exactly, due to a gap in the CO2 laser tuning range.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01425750
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  • 17
    Electronic Resource
    Electronic Resource
    Mechanisms of anion formation in O2, O2/Ar and O2/Ne clusters; the role of inelastic electron scattering (1992)
    Springer
    The European physical journal 25 (1992), S. 77-85 
    Details
    ISSN: 1434-6079
    Keywords: 34.70.+e ; 34.80.Gs ; 36.40.+d ; 34.80.−i
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Measurements are reported on the formation of negative ions in O2, O2/Ar and O2/Ne clusters aimed at establishing the mechanisms of anion formation and the role of inelastic electron scattering by the cluster constituents on negative ion formation in clusters. In the case of pure O2 clusters the main anions we detected are of two types: O−(O2) n≧0 and (O2) n ≧1− . The yields of O−(O2) n showed maxima at 6.3, 8.0 and ∼14.0 eV and the data suggest O− as their precursor; the maxima at 8 and ∼14 eV are due to the production of O− via symmetry forbidden dissociative attachment processes in O2 at these energies which become allowed in clusters. The yields of (O2) n − showed a strong maximum at near-zero energy (∼0.5 eV) and also at 6.3, 8 and ∼14 eV. With the exception of the near-zero energy resonance, the (O2) n − anions at 6.3, 8 and ∼14 eV are attributed to nondissociative attachment of near-zero energy “secondary” electrons to O2 clusters. The slow secondary electrons result predominantly from scattering via the O 2 − negative ion states of incident electrons with energies in their respective regions. Similar results were obtained for the mixed O2/rare gas clusters except that now a feeble and distinctly structured contribution in the yields of O−(O2) n , (O2) n − (and Ar(O2) n − ) was observed at energies 〉10 eV. These anions are believed to have the lowest negative ion states of Ar*− (Ne*−) as their precursors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01437522
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  • 18
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    Theoretical study of the 4f photoemission spectrum in Au55 aggregates (1995)
    Springer
    The European physical journal 32 (1995), S. 337-341 
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    ISSN: 1434-6079
    Keywords: 36.40.+d ; 79.60.−i ; 36.20.Kd
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In the photoemission process of a core level electron a satellite structure may appear due to the simultaneous excitations of valence electrons (many-electron effects). We study this phenomenon in Au55 aggregates. In this calculation we assume that the excitations can be limited to the 6s electrons which are described by means of tight-binding Hamiltonians in the initial (no core hole) and the final (hole present on a core level) states. An extension of a Anderson's formula strictly valid for the bulk is discussed and the possible use of the phase shift concept is analyzed. Our calculated satellite structure depends only on two parameters: Δ, the core hole attractive diagonal term and β, the normal transfer integral. We fix Δ/β=3 by comparison of our results to experiment performed on Au55 (P Ph3)12Cl6 compounds. The various experimental features are roughly reproduced by the calculation (number of peaks as well as their intensities and positions). Another interpretation of the experimental structure was proposed in the original experimental work. A more extensive investigation on other polyhedral metallic aggregates is necessary for allowing a choice between the two models.
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    URL: http://dx.doi.org/10.1007/BF01437278
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  • 19
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    Direct temperature measurement in alkali halide cluster beam (1995)
    Springer
    The European physical journal 34 (1995), S. 135-138 
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    ISSN: 1434-6079
    Keywords: 71.50.+t ; 36.40.+d
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The temperature of a sodium fluoride cluster beam produced by laser vaporization is estimated from the rotationally-resolved laser spectroscopy of the Na2 dimer. The cluster beam is obtained by laser vaporization of a sodium rod in a mixture of helium containing a small amount (1%) of SF6. Both rotational and vibrational temperatures (respectively 170 K and 400 K) are much higher than expected from a simple theoretical model of a supersonic beam. These temperatures can be lowered to 70 K and 250 K respectively by cooling the nozzle to liquid nitrogen temperature.
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    URL: http://dx.doi.org/10.1007/BF01439388
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  • 20
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    Theory for the atomic shell structure of the cluster magnetic moment and magnetoresistance of a cluster ensemble (1995)
    Springer
    The European physical journal 35 (1995), S. 273-278 
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    ISSN: 1434-6079
    Keywords: 36.40.+d ; 72.15.Gd ; 75.30.Cr
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present a simple theory for the cluster size dependence of the average cluster magnetic moment of transition metal clusters. Assuming a local environmental dependence of the atomic magnetic moments, the cluster magnetization exhibits a magnetic shell structure, reflecting the atomic structure of the cluster. Thus, the observed oscillations of the average cluster magnet moment may serve as a fingerprint of the cluster geometry. We also discuss the giant magnetoresistance (GMR) exhibited by an ensemble of magnetic clusters embedded in a metallic matrix. It is shown that the magnetic anisotropy affects strongly the magnetization of the cluster ensemble under certain conditions. Since the GMR depends on the cluster ensemble magnetization, it can be used to determine the cluster magnetic anisotropy energy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01745530
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  • 21
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    Photoionization studies of free sodium ammonia clusters (1992)
    Springer
    The European physical journal 22 (1992), S. 651-658 
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    ISSN: 1434-6079
    Keywords: 36.40.+d ; 33.80.Eh ; 82.40.Dm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Free sodium ammonia clusters Na(NH3) n up ton=45 were generated in a pickup source by injecting a beam of neutral sodium atoms into the expansion zone of a piezo driven pulsed nozzle. The clusters thus formed are studied by one-photon ionisation in the region of 266 nm to 520 nm, time-of-flight mass spectrometry as well as photoelectron spectrometry. Ionisation thresholds for clusters up ton=18 and dissociation energies for the neutral Na(NH3) n up ton=6 are reported.
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    URL: http://dx.doi.org/10.1007/BF01426368
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  • 22
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    Sub-picosecond laser ionization of free C60 and C70 at 248 nm (1992)
    Springer
    The European physical journal 23 (1992), S. 195-196 
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    ISSN: 1434-6079
    Keywords: 36.40.+d ; 33.80.Rv
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Delayed ionization is found to be absent for sub-picosecond laser excitation of free C60 and C70 at 248 nm. The autocorrelation trace obtained for C 60 + in a laser time-of-flight (TOF) mass spectrometer using two time-delayed and collinear 248 nm ultrashort laser pulses has a width of 1.1 ps (715 fs for sech2 pulses), in agreement with the laser pulse duration measurement in NO gas. Both above observations can be explained by direct ionization of C60 via coherent two-photon absorption by the high intensity sub-picosecond 248 nm laser excitation avoiding the channel leading to delayed ionization.
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    URL: http://dx.doi.org/10.1007/BF01437394
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  • 23
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    Electron impact ionization of silver clusters Ag n ,n≦36 (1992)
    Springer
    The European physical journal 22 (1992), S. 517-520 
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    ISSN: 1434-6079
    Keywords: 36.40.+d
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Electron impact ionization of gas phase silver clusters Ag n ,n≦36 has been achieved in the threshold region. The vertical ionization potentials in this region clearly demonstrate the evidence of shell effects as well as a distinct even-odd oscillation up ton≃20. Their general size dependence is somewhat different from that of the alkali metal clusters due to the presence of thed-electrons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01426093
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  • 24
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    Resonant two-photon two-color photoionization (R2P2CI) spectra of aniline-Ar n clusters: Isomer strutures and solvent shifts (1992)
    Springer
    The European physical journal 22 (1992), S. 529-539 
    Details
    ISSN: 1434-6079
    Keywords: 36.40.+d ; 35.20.Vf ; 33.80.Eh
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present resonant two-photon two-color photoionization (R2P2CI) spectra of a series of Aniline-Ar n complexes (n=1−6). An apparently anomalous blue shifted spectra for An-Ar3 is explained by a modified spectral shift additivity rule which assigns different shifts to different relative positions of the Ar with respect to aniline. Evidence is presented for the existence of several isomers of clusters withn≧2. It is shown that, by changing the nucleation conditions, it is possible to control the relative populations of the various isomers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01426095
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  • 25
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    Distribution of interatomic distances in large metallic clusters (1992)
    Springer
    The European physical journal 22 (1992), S. 541-545 
    Details
    ISSN: 1434-6079
    Keywords: 36.40.+d ; 61.50.Cj
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Spherically averaged pseudopotential (SAPS) calculations have been done for Mg n clusters, withn up to 250 within the framework of density functional theory. The electronic structure is computed resorting to the Thomas-Fermi-Dirac-Weizsäcker (TFDW) approximation for the kinetic energy. The equilibrium geometries have been obtained by minimizing the total cluster energy with respect to the atomic positions using the steepest-descent method. The ground state geometries obtained in this way are formed by spherical atomic shells, the number of them increasing with cluster size, up to a number of four for the biggest sizes considered here. An analysis of the distribution of the interatomic distances shows that the more internal is the shell, the more contracted are the interatomic distances. This effect diminishes progressively with increasing cluster size. For the purpose of comparison, similar calculations have been done with Cs n clusters in the same size range, allowing us to reproduce previous results obtained using a more elaborated density functional technique (Kohn-Sham method). The inhomogeneous contraction of interatomic distances then appears as a general fact for simple metallic clusters and not only for alkaline ones.
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    URL: http://dx.doi.org/10.1007/BF01426096
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  • 26
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    Simulation of cluster impact fusion (1992)
    Springer
    The European physical journal 22 (1992), S. 547-551 
    Details
    ISSN: 1434-6079
    Keywords: 36.40.+d ; 79.20.Rf
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report molecular dynamics simulations of the impact of TiD clusters on TiD targets. In each cluster collision the total fusion probability seems to be due to a single deuterium deuterium collision. The kinetic energies of incident deuterium atoms gradually level off around the initial cluster energy, but do not reach the high energy tail of a corresponding Maxwell-Boltzmann distribution. Neither any other support for a thermonuclear fusion mechanism was observed. On the contrary, our simulations imply that the enhanced fusion rate is rather due to channeled many atom collision cascade type mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01426097
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  • 27
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    Ionic core effects on the mie resonance in lithium clusters (1995)
    Springer
    The European physical journal 32 (1995), S. 329-336 
    Details
    ISSN: 1434-6079
    Keywords: 36.40.+d ; 78.20.−e
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We investigate the effects of the atomic cores on the Mie resonance in lithium metal clusters, perturbing a jellium Hamiltonian with zero-range pseudopotentials. The resonance is red-shifted with respect to the classical formula by core effects, most important of which is the increased effective mass due to the core potentials. Much of the large shift seen in lithium clusters is thereby explained if the strength of the pseudopotentials is taken from band structure calculations. However, such pseudopotentials cause the resonance to be greatly broadened, contrary to observation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01437277
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  • 28
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    Mass distribution of cluster ions produced from laser ablation of metal-composite-oxides Y-M-Cu-O (M=Ba, Sr, Ca, Mg) (1995)
    Springer
    The European physical journal 34 (1995), S. 257-261 
    Details
    ISSN: 1434-6079
    Keywords: 36.40.+d ; 35.20.Wg ; 34.10.+x
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Laser ablation of YMCuO metal-composite-oxides (M=Ba, Sr, Ca, Mg) in high vacuum produced cluster ions with various sizes and compositions. Mass spectra of the cluster ions were recorded by a home-built time-of-flight (TOF) mass spectrometer and the mass distributions were analyzed by a statistical model. For YBa2Cu3O7−x (YBCO) high-Tc superconducting samples, six series of cluster ions were observed. Replacement of barium in the metal-composite-oxide sample with other alkaline earth metal, such as strontium, calcium, or magnesium, not only removed the superconductivity, but also changed the compositions and distributions of the laser generated cluster ions. For instance, copper was only found in the compositions of cluster ions generated from YBCO sample. From comparison of the experimental results, interactions among components of the metal-composite-oxides and the function of alkaline earth metal in superconducting material were discussed.
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    URL: http://dx.doi.org/10.1007/BF01437571
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