The physical limiting procedure normalisation

The key quantity in the calculation of experimental observables is the collision amplitude (6.13). The box-normalised collision amplitude for the wave packet is given for t = 0 by using (6.26). 

The significance of this expression is that the divergent integral (6.13) over all space has been replaced by an integral over the finite volume in which V is nonzero, and other quantities that are easily handled. 

We first consider the limit L — oo, applied to R q We normalise both the channel and collision states of (6.28) in the same way by considering the part of that describes the relative motion of the projectile and the target. After taking the limit this is an eigenstate of momentum kj). 

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