1. Department of Applied Chemistry, Osaka Prefecture University, Gakuen-cho 1-1, Sakai, Osaka 599-8531, Japan
2. Department of Electronic Engineering, Osaka University, Yamadaoka 1-1, Suita, Osaka 565-0871, Japan
3. Human Environment Systems Development Center, Matsushita Electric Industrial Company, Ltd., Seika-cho, Souraku, Kyoto 619-0237, Japan
4. Ion Engineering Research Institute Corporation, Tsuda-yamate, Hirakata, Osaka 573-0128, Japan