1. Laboratoire Aimé Cotton, Bât. 505, Centre d'Orsay, 91405 Orsay Cedex, France, Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70 F. Skaryna Ave., 220072 Minsk, Belarus, and Organic Intermediates and Dyes Institute, 1/4 B. Sadovaya Str., 103787 Moscow, Russia