IT IS A POLL! I would like to learn if you've ever heard of the positive charge atomic form-factor before my asking this question. The positive charge atomic form-factor fnn'(q) stands at the nucleus charge Z and describes the positive charge cloud in atoms for elastic scattering at large angles (n→n). It also describes inelastic scattering channels - hitting nucleus by a projectile excites an atom (n→n'). The elastic and inelastic positive charge atomic form-factors are entirely determined with atomic wave functions ψn(r) and they have nothing in common with the Hofstadter form-factor describing the proper nucleus size. The positive "cloud" size may be very big if the initial and the final atomic states ψn(r) are excited and metastable, like in Rydberg atoms. This is just effect of the nucleus motion around the atomic center of inertia. Physically it is of the same nature as the negative (electron) charge atomic form-factor Fnn'(q). The numerical difference is just in the "could" sizes - the negative one is larger (an), the positive is smaller ((me/Mp)an for Hydrogen, for example). Correspondingly the scattering angles where these form-factors work differ essentially - at small and large angles. The details can be found in my article "Atom as a "dressed" nucleus" in arXiv (http://arxiv.org/abs/0806.2635). Do not hesitate to leave your answer and thanks for participating in this poll. Bob_for_short.