Metastable deexcitation spectroscopy (MDS) is one of the most powerful techniques for studying electronic properties of the outermost layers of solid surfaces. Metastable atoms of rare gases impinge on solid surfaces and electrons are emitted as a result of electronic energy transfer. The principles of MDS applied to solid surfaces are described. Two mechanisms of deexcitation of metastable atoms are discussed in the cases of clean alkali and transition metal surfaces. The effects of adsorption of gases such as O and CO are also shown. Several applications of MDS are described for evaluation of new surface materials.
The present paper deals with restoration of the catalytic activity of Raney nickel deactivated by heat treatment (1), electrochemical oxidation (2) slow oxidation in water by dissolved oxygen (3) and quick oxidation in air (4). The plate-type Raney nickel catalyst used in this experiment is convenient for this particular ion-bombarding technique. The fine powder catalyst usually used could not be applied to this technique. The catalysts deactivated by the methods (2, 3) were activated by means of radio frequency diode sputtering system. An ordinary nickel plate and Raney nickel catalyst heated at high temperature (method 1) or burned in air (method 4) could not be activated by argon ion bombardment, because of the strong Ni-Ni and Ni-O bonds. The appearance of activity in Raney nickel catalyst generally results from amorphous nickel structure, when aluminum is leached from Ni-Al alloy. Activity restoration of catalyst by argon ion bombardment is satisfactly explained on the basis of the same reason.
Solid state bonding of Al2O3 and SUS 321 stainless steel was carried out under pressures above 0.19kgf/mm2 at temperatures above 900K in a vacuum using the surface precipitation behavior of TiC. Bonding strength was evaluated and bonding mechanism was discussed. Bonding of Al2O3 to SUS 321 occurred at temperatures above 1000 K. However, SUS 321/Al2O3/SUS 321 system of measurable strength could be fabricated at temperatures above 1200 K. Bonding strength was measured with an Instron-type machine. The maximum value of bonding strength was 2.2kgf/mm2, which was obtained at 1200 K and under pressure of 0.75kgf/mm2. The change of the composition at the interface between Al2O3 and SUS 321 was observed with EPMA in order to examine bonding mechanism. The result of EPMA showed that Ti condensed at the interface. It was considered that titanium combined with carbon to form TiC. TiC precpitated at the interface between Al2O3 and SUS 321, and also penetrated into the pore existed in Al2O3. Therefore, the strong bonding between Al2O3 and SUS 321 originated from the precipitation of TiC at the interface.
The electronic state of Rhodamime B being hold on potassium chloride microcrystal (Rh B/KCl) is studied by means of the photoacoustic spectroscopy (PAS). A photoacoustic spectrum of the dried sample shows the prominent absorption maximum which is shifted to the longer wavelength side than the reported location of that in aqueous solution. This shift is elucidated by the instability of the ground state of dye molecules. It is suggested that this instability is introduced through the molecular deformation which is caused by the strong Coulombic interaction between Rh B zwitterions and the KCl crystal lattice. The signal height at the maximum decreases as a result of the absorption of airborn water. This is supposed to be caused by the lactone ring formation in a part of dye molecules.
For the cause for the layer-dependent shifts of the inverse photoemission spectra from adsorbed xenon atoms, which is recently argued among researchers, we demonstrate that the shift is due to the final state effect.
Organic dyes have been noticed because of their excellent thermal properties for use in optical recording. But, organic dyes having strongly optical absorption at diode laser wavelength (_??_800nm) was hard to find. Thus the practical use of organic dyes for the optical disk memory was behind the tellirium system. More recently, organic dyes which absorb laser light strongly at near-infrared region are intensively searched, and their use for the optical disk memory is now being possible. In this review, the representative organic dyes found are described.
Time-resolved (vibrational) electron energy loss spectroscopy (TREELS) has made the “direct observation” of surface reactions possible. In this paper are reviewed the experimental methods and their typical results obtained. The fields to which TREELS may be applied are also discusssed