The energy transfer and spectra behaviour of DMANS (4-Dimethylamino -4'-nitrostilbene)in solution and polystyene (PS) matrix have been studied by fluorescence spctroscopy and time corrected single photon counting technique. When the solvents polarity increased

DMANS fluorescence intensity and lifetime decreased and a red shift of fluorescence emission maximum was pb- served.For instance

in benzene with various concentration (from 1% to 28%) of cyclohexanol (the solvents polarity increased gradually) DMANS fluorescence emission maximum shifts from 578nm to 628nm and the fluorescence lifetime decreases from 2.5ns to 0.21ns. It can be interpreted that in polar medium electron transfer in DMANS molecule became more easily and the energy difference between excited state and ground state decreased. In PS matrix

when DMANS concentration increased

the PS fluorescence intensity and lifetime were decreased and the DMANS lifetime was decreased also. The dete are shown in the table.Table Lifetime of DMANS and PS in scintillators.When the lifetime was measured at 330nm

the PS emission was a single exponential decay owing to the energy transfer from PS to DMANS

the lifetime of PS was decreased as increasing DMANS concentration. When the lifetime was measured at 540nm

the DMANS fluorescence was a double exponential decay.The fast decay reflected the decay of direct excitation on DMANS and the slow one reflected the influence of the energy transfer from PS to DMANS.We used Stern-Volmer equation to calculate the PS quenching constant (K

q

=3.0X×10

9

M

-1

S

-1

) and and the decay rate constant of PS (K=1/τ

0

=4.3x×10

7

M

-1

S

-1

).It means energy transfer from PS to DMANS efficiently

but the longer lifetime of PS will apparently influence the decay of the DMA-NS fluorescence scintillator. This study indicated that medium polarity effects scintillator's fluorescence quantum yield

absorbtion peak

emission peak and decay time.So it is important to select a suitable medium for getting a thigher efficiency

fast response scintillators.