1. Fundamental Sciences Directorate, Pacific Northwest National Laboratory, P. O. Box 999, MSIN K2‐57, Richland, WA 99354 (USA), Fax: (+1) 509‐375‐6660
2. Chemistry Department, University of Oregon, Eugene, OR 97403 (USA)
3. Chemistry Division, Los Alamos National Laboratory, MSIN j514, Los Alamos, NM 87507 (USA)