Relativistic effects of laser doppler velocimeters using one light beam with two frequencies

Relativistic effects of laser Doppler velocimeters (LDV's) are discussed and novel LDV systems are proposed. If the direction of the scattered light makes a right angle with the flow direction, relativistic effects completely disappear no matter how high the velocity of a moving particle becomes. The proposed LDV's involve that the velocity can be measured from one scattered light beam with two different single frequencies. It is also predicted that the usual optical heterodyne-detection techniques can be made applicable to measure even ultra-high velocities up to the region where relativistic effects should be taken into account.     

The control of very low oxygen partial pressures with stabilized zirconia cell

Control of very low oxygen partial pressures was performed in the range of 10⁻²¹-10⁻²⁴ Pa at 750°C by pumping oxygen into the purified hydrogen stream with a stabilized zirconia cell. The oxygen partial pressures were monitored by a stabilized zirconia sensor. The stabilized zirconia oxygen sensor was calibrated by H₂-CO₂ gas buffer mixture in the range of oxygen pressure from 10⁻¹⁷ to 10⁻²¹ Pa, and oxygen partial pressures below 10⁻²¹ Pa were measured by extrapolating the calibration line to very low oxygen partial pressures. The lowest oxygen partial pressure controlled was 10⁻²⁴ Pa at 750°C, which was limited by gas leaks in the system and also by the reduction of the ionic transference number in solid electrolyte used as the oxygen pump.     

Configuration-coordinate model for photodarkening in amorphous As2S3

Annealing characteristics of photodarkening have been studied experimentally in order to investigate a model represented by a configuration diagram which includes excited and ground states. Barrier heights of the ground states, having double wells, are fairly scattered around 0.5 ～ 1.5 ev from site to site, and the energy difference between the wells is 0.1 eV. The relaxation energy of the excited states is estimated to be 0.05 eV. The fact that band-gap illumination determines the position of optical absorption edges of the specimen irrespective of the previous history, is understandable with this model. Further, it is shown from annealing kinetics that the origins of the photodarkening and mid-gap-absorption are not the same.     

Isotope effects on vibronic coupling of pyrazine

The vibronic couplings of pyrazine-d₀ and pyrazine-d₄ between the lowest electronic excited states ¹B_3u(n, π^*) and ¹B_2u(π, π^*) through the out-of-plane CH bending vibration ν_10a(b_1g) have been studied from the Raman, electronic absorption and fluorescence spectra. The isotope effects on the scattering cross section of the ν_10a Raman line, the vibrational potential in the ¹B_3u(n, π^*) state and on the frequency change of the ν_10a vibration between the ground and the lowest electronic excited states are well explained by conventional Herzberg-Teller coupling mechanism. However, the intensities of the vibronic bands in the electronic absorption and fluorescence spectra are hardly explained with this coupling mechanism.     

Rapid adsorption and entrapment of benzoic acid molecules onto mesoporous silica (FSM-16)

Changes in the molecular state of benzoic acid (BA) in the presence of folded sheet mesoporous material (FSM-16), which has uniformly sized cylindrical mesopores and a large surface area, were assessed with several analyses. When BA was blended with FSM-16 for 5 min (BA content=30%), the X-ray diffraction peaks of BA crystals disappeared, suggesting an amorphous state. Fluorescence analysis of the mixture showed a new fluorescence emission peak for BA at 386 nm after mixing with FSM-16. Fluorescence lifetime analysis of the BA component in the mixture at 386 nm showed a longer lifetime in comparison with that of BA crystals. The solid-state (13)C CP/MAS and PST/MAS NMR spectra of the mixture with FSM-16 showed a significantly different spectral pattern from the mixture with nonporous glass, whose NMR spectra were identical to those of BA crystals. These results indicate that BA molecules disperse quickly into the hexagonal channels of FSM-16 by a simple blending procedure and adsorbed BA molecules had clearly different physicochemical properties to BA crystals.     

Effects of surface roughness of a moving test body on laser-interferometric displacement measurements

Displacement measurements by laser-homodyne or laser-heterodyne methods are dicussed analytically with respect to the relevant surface roughness. Expressions of the output signal and its signal-to-noise ratio are derived on the basis of gaussian statistics of the roughness. The roughness does not impose restrictions on the measurable minimum displacement but degrades the signal-to-noise ratio of the output signal.