Whats the deal with the pixel scattering function in WFPC2?
The pixels of a CCD are not separate bins, isolated from their neighboring pixels. They are defined in one direction by the electric fields of the electrodes, which are implanted on the surface of the silicon layer. In the other direction there are channel stops. Neither of these “barriers” is completely impervious. When a photon strikes within a pixel, it is converted to an electron, which is attracted to the electrode. However, the electric field in some parts of the pixel is weak enough that some electrons can move into an adjacent pixel. At shorter wavelengths, photons can also be scattered by the electrode structure before they are converted to electrons. Some of the photons are simply scattered away and never detected, and some electrons may be absorbed before reaching the electrodes. Either way, some charge leaks into other pixels while a lesser amount is completely lost, effectively blurring the image. This is called charge diffusion. Photons striking in the center of a pixel h
