 the wavefunctions at specific points in order to
 calculate the photoelectron spectrum at a point far in the box as proposed in
 A. Pohl, P.-G. Reinhard, and E. Suraud, <i>Phys. Rev. Lett.</i> <b>84</b>, 5090 (2000).
</li>
<li><b>pes_mask</b>:  Calculate the photo-electron spectrum using the mask method.
 (D. Varsano, PhD thesis, page 159 (2006) http://nano-bio.ehu.es/files/varsano_phd.pdf).
<br><br>
 For this to work, masking boundaries are necessary (<tt>AbsorbingBoundaries = mask</tt>).
</li>
</ul>
</p>