FEMTOSECOND DYNAMICS AND STIMULATED-EMISSION FROM THE S-2 STATE OF A LIQUID-CRYSTALLINE TRANS-AZOBENZENE

The excited-state S-2 dynamics of an azobenzene derivative, trans-BMAB , was investigated in solution by femtosecond transient absorption and picosecond single-photon timing fluorescence spectroscopies. The fluo rescence was observed at 400 nm with a lifetime similar to 250 fs. The S-1 state with an absorption maximum at 410-415 nm was formed with a time constant of similar to 250 fs from the S-2 state followed by rela xation with a lifetime of similar to 2.3 ps in n-hexane. The stimulate d emission from the S-2 state overlapped with the femtosecond transien t absorption spectra just after excitation, which was confirmed by pol arization absorption spectroscopy. (C) 1998 Elsevier Science B.V. All rights reserved.