We request beam time on VESUVIO spectrometer in order to characterise the effect of electron-phonon coupling on the nuclear dynamics of superconductors. This proposal is motivated by recent experimental evidence of a broadening of Niobium momentum distribution (and increase in the mean kinetic energy) when a Niobium slab is cooled below the critical temperature (9.2 K). In order to investigate the sensitivity of VESUVIO to the effect of electron-phonon coupling in superconductors, and to clarify if the observed mechanism is a general one, we propose to measure the momentum distribution of several superconductors across superconducting phase transition. In particular, we want to measure two elemental superconductors, Vanadium and Tantalum (having the same bcc structure of Niobium and belong to the same group in the periodic table), and two Niobium-based superconductors, Nb3Sn and Nb3Al.