Fourier transforms, absorbing the wavepacket at grid edge

Fourier transforms, absorbing the wavepacket at grid edge 

Ideally we would wish to start the wavepacket at a very large separation of the reactants and to continue the calculation until all of the wavepacket had either rebounded or reacted and the products were separated by a large separation, to do this would require impossibly large grids. 

To avoid these problems the wavepacket is stopped from reaching the edge of the grid by imaginary absorbing potentials. Consider the wavepacket propagation equation (1.2). Let 

Extensive use is made of these complex absorbing potentials. There has been a lot of discussion of the detailed form they should take [15, 16]. They must also be sufficiently strong to absorb the entire wavepacket. Our findings, after detailed study, are as follows. 

The best parameters to choose for these potentials have also been listed [16]. 

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