In this work is shown that by measurement of the velocity of excited particles ejected by a beam of fast ions from the surface of a solid, some characteristics of its electronic level structure may be determined. The velocity spectrum of Ti, Na and Li atoms ejected respectively from targets of titanium and NaCl- and LiF-crystals by a beam of Ar+ ions was investigated. From an analysis of the obtained velocity spectra the following conclusions were deduced: (1) the work function of Ti must lie in the energy interval 3.8-4.15 eV, (2) the width Xof the conductivity bands of NaCl and LiF has the value XNacl < 1.019 eV and XLiF < 0.381 eV.