processes of a 1,2-bis(thiazolyl) perfluorocyclopentene photochromic diarylethene 1 with extremely low reaction yield under steady state irradiation in chloroform solution (1.3 × 10−3) was investigated by means of picosecond and femtosecond laserphotolysis methods. The cycloreversion reaction was drastically enhanced by more than two orders of magnitude (ca. ×400) by a picosecond 532 nm laser excitation