Toshihiko Arai

Highly Sensitive Laser Absorptiometric Method Using Triple-Prism Multireflection System

To obtain high sensitivity in absorptiometry using a standard cell with a 1 cm light path length, two new optical systems have been designed. The sensitive absorptiometric system using the twin or triple prism coupling method provides 10-18 times higher sensitivity than does the ordinary absorptiometer.

Hg+ ion density in low‐pressure Ar‐Hg discharge used for a mercury lamp

The Hg+ ion density on the tube axis in the low‐pressure Ar‐Hg discharge lamp with 12 mm i.d. has been first measured under various bath temperatures and discharge currents with a modified absorption method. The radial distribution of the Hg+ ion density also has been determined.

Measurement of Hg 6p 3P0,1,2 state densities in the low‐pressure positive‐column Ar‐Hg discharge using 8s 3S1–6p 3P0,1,2 lines

The measurement method of Hg 6pu20093P0,1,2 state densities using the 8su20093S1–6pu20093P0,1,2 lines of less absorption has been developed, and the Hg 6pu20093P state densities on the tube axis in the low‐pressure positive‐column Ar‐Hg discharge of 12 mm inner diameter used for the mercury lamp have been measured.

Reactive ion etching of CVD diamond thin films in O2/CF4 plasma

Reactive ion etching of chemical vapor deposition (CVD) diamond thin films was investigated in O2 gas plasma mixed with CF4 and electrodes distance. The optical emission spectrum of plasma species in excited electronic states was measured in order to know the information of relationship between etching rate of diamond and the concentrations of key reactive species. The RF power (13.56 MHz) was fixed at a constant 100 W. The large etching rate was obtained by using O2/20% CF4 at electrodes distance of 1.5 cm, O2 flow rate of 20 sccm and total pressure of 20 Pa. Etched diamond surface was observed SEM micrographs. The diamond surface in O2/20% CF4 plasma was smoother as compared with one in pure O2 plasma. The emission intensity of O had a peak around O2/20% CF4. The results of etching rate and emission intensity agree well with each other.

Influence of wall heating on CF2 radical in CF4 hollow cathode discharge plasma

The behavior of CF2 radicals was studied as a function of the temperature of the wall of the cylindrical cathode in dc-pulsed CF4 hollow cathode discharge plasma. Laserinduced fluorescence was used to examine the temporal behavior and radial distribution of CF2 radical density. The CF2 radical density increased about six times in magnitude by changing the wall temperature between 22°C and 100°C. The surface loss probability for CF2 radicals was estimated from the radial distribution of the CF2 radical density in the active plasma. The results show that the increase of the CF2 radical density in the heated wall can be interpreted as a decrease in the surface loss probability of CF2 radicals.