In this paper

a theoretical model based on the Grabowski's theory of twisted intramolecular charge transfer(TICT)excited state is propo-sed to deal with the formation dynamics of TICT excited state.It is shown that the TICT excited state is a.main nonradiative relaxation path of S

1

p

singlet state:k

nτ

p

=k

ic

+k

isc

p

+k

pt

.The fluorescence lifetime of 7-aminocoumarin C1F and C2F in alcohols was measured using the time-correlated single photon counting methods.And the effects of different solvent on lifetime(τ

f

)

nonradiative relaxation rate(k

nτ

)and the formation rate of TICT excited state(k

pt

)were investigated.It is found that k

pt

-1

of cournarin molecules depends on η/T in.the monobasic alcohols

and increases nonlinearly with η/T in polybasic alcohols.The former agrees with Debye-Stokes-Einstein's theory.And it is also found that H-bond effect among alcohol molecules and between solute and alcohol molecules is an important factor which affects the process and can not be neglected.