As {HEAD ~ an alternative} to calculating {TAIL ~ the fluorescence lifetime}, the integral of the fluorescence signal after the pulse excitation can be measured 
to calculating
As { HEAD ~ an alternative } to calculating { TAIL ~ the fluorescence lifetime } , the integral of the fluorescence signal after the pulse excitation can be measured
OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH