1. Institute
of Chemistry, Academia Sinica, Taipei, Taiwan 11529, R. O. C.
2. Graduate
Institute of Photonics and Optoelectronics and Department of Electrical
Engineering, National Taiwan University, Taipei, Taiwan 10617, R. O. C.
3. National
Synchrotron Radiation Research Center, Hsinchu, Taiwan 30077, R. O. C.