On Metal-Atom Clusters IV. Photoionization thresholds and multiphoton ionization spectra of alkali-metal molecules

The investigation of electronic and structural parameters of metal molecules as a function of size may be decisive for understanding and control of heterogeneous catalysis with finely divided metals. Metal-atom clusters can be prepared by several methods, most of which yield a molecular mixture only. Expansion of an atomic vapour into vacuum through a supersonic nozzle creates a complex cluster-spectrum which has been investigated by photoionization using a mass-spectrometer as selective detector. Broad band single photoionization ( PI. ) yields the abundances and ionization thresholds for Na_x(x?16), K_x(x?12) and Na_xK_y(x+y?6). Rough indications about other deactivation channels of excited alkali-molecules are obtained from an analysis of the photoionization efficiency (PIE.) curves. Two-photon PIE. curves with narrow-band (laser) light sources give an accurate photoionization threshold value and detailed information on ionization processes. Two-photon ionization spectra via a real intermediate state reached by laser excitation are equivalent to normal absorption spectra, if the exciteation step is controlled by the true transition probabilities. By investigation of the power dependence of the ion current of Na as a function of the wavelength of the tunable cw dye laser (excitation) and of the ionizing Ar⁺- or Kr⁺-laser, conditions under which true spectra are obtained have been clarified, in good agreement with a photon-kinetic model of the processes involved. Vibronic and rovibronic spectra of several transitions in Na₂ and K₂ have been measured. Similarly a spectrum of Na₃ has been determined mass-selectively. The scope of the new method for an absorption spectroscopy in molecular beams is discussed.     

Optical absorption induced by impurities distributed at random

The optical absorption coefficient has been calculated in the case of resonant band modes, using the frequency spectrum discussed in a previous paper 1. The width of the absorption line does not show any great variation with the density of impurities whereas the position of the absorption maximum is shifted.     

Das Gleichgewicht eines Wasserringes mit freier Oberfläche in einem rotierenden Hohlkörper

Summary The problem of the critical speed of revolution of a hollow rotor which has a water ring revolving inside and with it, is investigated and it is found to be identical with the critical speed of revolution of a rotor completely filled with water. As the calculation of the oscillations of the water ring itself shows, dangerous resonances with the rotor oscillations need not be expected.      

Diaryl-disulfimide als Urtitersubstanzen

Ohne ZusammenfassungDiplomarbeit A. Ernst, Halle 1956.     

Betrachtungen zu den Hauptproblemen der mathematischen Aussenballistik

Summary The paper provides a short survey of the actual state of the theoretical exterior ballistics. In particular the fundammental equations defining the motion of a rotating projectile are given in a form suitable for numerical calculation. Then, using the argument that a projectile possesses full rotational and also mirror summetry, the explicit development of the force and moment components is given in terms of the linear and angular velocities. Finally this development is compared with the experimentally known aerodynamic coefficients and stability derivatives.