function TotalDecay = lifeFunc2com(params,Time,pp)


Amp1 = params(1); Amp2 = params(2);
Life1 = params(3); Life2 = params(4);
iback = params(5);
Dback = params(6);
TimeShift = params(7); % shift in time variable

TimeWithShift = Time + TimeShift;

 InterpolateInstResp=pp(TimeWithShift);

InstRespForCalc = InterpolateInstResp +1+iback;
InstRespForCalc2 = InstRespForCalc(2:end);InstRespForCalc2(end:end+1) = 0;

Decay1 = filter(Amp1*0.5,[1;-exp(-Time(2,1)/Life1)],InstRespForCalc*exp(-Time(2,1)/Life1)+InstRespForCalc2);
Decay2 = filter(Amp2*0.5,[1;-exp(-Time(2,1)/Life2)],InstRespForCalc*exp(-Time(2,1)/Life2)+InstRespForCalc2);

TotalDecay = Decay1+Decay2+Dback;