The possibility to obtain the electro-nuclear response functions from
the knowledge of their Stieltjes transforms is investigated. The deute
ron longitudinal response is taken as a test case. The Stieltjes trans
form is calculated using closure. This leads to a dynamical equation s
imilar to a bound-state Schrodinger equation, which can possibly be so
lved for few-body systems. Various methods of reconstructing the respo
nse are considered. Very good results are always obtained in the low-e
nergy region and for the elastic form factor. For a satisfactory descr
iption of the response function over a large energy range, the Stieltj
es transform must be known with a rather high precision. Only in speci
fic cases one may obtain surprisingly good results with less accurate
Stieltjes transforms.