Photoexcitation of a volume plasmon in C60 ions

Neutral C60 is well known to exhibit a giant resonance in its photon absorption spectrum near 20 eV. This is associated with a surface plasmon, where delocalized electrons oscillate as a whole relative to the ionic cage. Absolute photoionization cross-section measurements for C+60, C2+60, and C3+60 ions in the 17-75 eV energy range show an additional resonance near 40 eV. Time-dependent density functional calculations confirm the collective nature of this feature, which is characterized as a dipole-excited volume plasmon made possible by the special fullerene geometry.     

Levinson-like theorem for scattering from a Bose-Einstein condensate

A relation between the number of bound elementary excitations of an atomic Bose-Einstein condensate and the phase shift of elastically scattered atoms is derived. Within the Bogoliubov model of a weakly interacting Bose gas this relation is exact and generalizes Levinson's theorem. Specific features of the Bogoliubov model such as complex energy and continuum bound states are discussed and a numerical example is given.     

Über den zusammenhang von linienintensität und elementkonzentration im optisch dünnen bogenplasma

Based on a simple model of the free burning constant current arc (rectangular temperature pattern, no self-absorption), the intensity ratio of a line pair (analytical line/internal standard line) is investigated as a function of the analytical element concentration in the plasma. Assuming the concentration in the plasma to be unequivocally determined by the element concentration in the sample, the intensity-concentration relationships may be interpreted as working curves. It appears that these theoretical working curves are generally not linear and the slopes may deviate significantly from unity when plotted in logarithmic coordinates. The shapes of the working curves depend on parameters characteristic of the line pair under consideration (excitation and ionization energies, partition functions) as well as on the temperature and electron-density and their changes. The results obtained are illustrated by a calculated example.     

Experimental study of the photoemission of protons off12C using tagged photons in the energy range 200–385 MeV

Data are presented for proton emission off¹²C using tagged photons in the energy range 200–385 MeV. The protons are detected in a magnetic spectrometer. In addition, charged or neutral particles can be measured with a scintillation counter setup. Contributions to the proton energy spectra from primary pion production and quasideuteron reactions are separated using the coincidence data. The total¹²C(γ, p)X cross section is derived as a function of the photon energy. The data are compared to the predictions of an intranuclear cascade calculation. Final state interactions have to be taken into account to describe the data.     

The molecular properties of the positronium negative ion

The dynamics of the positronium negative ion is described in a molecular adiabatic approximation. It is shown, how the classification of the spectrum, propensity rules for radiative and non-radiative transitions and conditions for the occurrence of shape resonances can easily be derived within this approach. Propensity rules for two-photon processes are also derived and used to demonstrate the possibility of an absorption experiment from the ground state to excite a¹S^e shape resonance, which is unique to Ps^–.     

Measuring the top quark mass in the eµ channel: A study

We describe a simple method to measure the top quark mass in the channel that may be useful in Run II of D? detector. The method is validated by applying it to the Run Ib eμ data.