A review is presented of experimental investigations dealing with the ionization of various atoms and molecules in collisions with metastable rare gas atoms. The methods for determining de-excitation (Penning ionization) rate constants or cross sections; a W-value measurement, a static-afterglow, a flowing-afterglow, a beam and a pulse-radiolysis methods, are reviewed. Our results obtained by a pulse-radiolysis method are compared with those obtained by other methods. For theoretical investigations such as those based on a gas-kinetic collision model and an electron exchange model, the formalism and calculations for Penning ionization cross sections in collisions with atoms in metastable and resonance states are also reviewed, and our recent results are discussed from the viewpoint of a gas-kinetic collision model. Some aspects of the application of Penning ionization processes to gas lasers and the production of polarized electrons and ions are also presented.
We studied the minority carrier lifetime in localized volumes in dislocation free silicon, using laser diode as the carrier injection source (1 mmφ, spot). The minority carrier lifetime can be estimated independent of sample thickness provided the thickness is of about the same order as the carrier diffusion length. The lifetime of the quenched samples increases from the surface to the interior and depends on the quenching speeds. It finally assumes oscillating values with a period of 100)_??_200μm in both quenched and as-grown silicon. By lithium diffusion, the increments of lifetime in A type swirl rich region are larger than those of the swirl lean region in swirl contained silicon. Although the minority carrier lifetimes in samples of silicon quenched from 700°C were not changed, those quenched from 400°C, 500°C and 600°C showed an increase by lithium diffusion.
Experimental results on electron-beam pumping of mixture gases HCl:Xe:Ar and BCl3: Xe: Ar are described. Efficient laser action is obtained on the 308-nm band of XeCl excimer. A compact, economical electron-beam generator is designed and constructed for a pumping source of excimer lasers, and its characteristics are reported. When the field emission diode is directly driven by a 12-stage 550 kV coaxial Marx-bank circuit with a stored energy of 101J, the electron-beam current diposited to the laser gas is 4 kA with 25 ns FWHM. The output energy of XeCl laser is 173 mJ (8.6 J/l) using HCl as a Cl-donor. The output energy is comparable with those of rare-gas fluoride lasers.
An improved copper decoration technique is described. The technique eliminates such a disadvantage of the conventional techniques as the formation of alloyed surface layers. Silicon wafers are immersed in HF solution containing a small quantity of Cu2+ ions and are covered with copper layer, followed by annealing in dry O2. The quantity of copper atoms in annealed silicon is proportional to the Cu2+ concentration of the HF solution. By selecting the solution with a proper Cu2+ concentration not to exceed the solubility limit for copper in silicon, the formation of alloyed surface layers is avoided. Thus the specimens can be immediately prepared for X-ray section topography to investigate both the surface and bulk of silicon wafers. The technique has been applied for studying swirl defects. It has allowed us to observe the gettering effect associated with swirl defects.
Noise properties of positive column type metal ion lasers (He-Cd and He-Se) were studied to make clear the noise origins. Noise level, noise spectra, correlation between laser noise and discharge current noise, and dispersion relation of side light noise were measured. Interpretation of the acquired data convinced us that the noise origins are moving striations and related fluctuations rather than metal vapour pressure fluctuations.
The properties of the light of single longitudinal mode obtained from a laser subjected to a transverse magnetic field giving rise to the Zeeman separation equal to the longitudinal mode interval, are studied by means of the polarization analysis and optical beating techniques. The lasers studied are internal mirror type of 26-28cm cavity length, and oscillate with 2-3 longitudinal modes under normal conditions. The light thus obtained was found to be composed of two almost linear orthogonally polarized components with different frequencies. The frequency difference between the two components differs from one tube to another and changes with the magnetic field and the tuning of the cavity. The frequency difference normally stays within the range of a few hundred kHz. The frequency difference as well as the wavelength of the laser oscillation can be stabilized by tuning the cavity referring to the polarization of the light. It was also found that laser oscillation of a single frequency can be obtained when the laser tube is set at a particular azimuthal angle to the magnetic field.