The ICARUS and future liquid argon neutrino experiments generate demand for evaluating the spectral function of argon. In this paper we use oxygen nucleus as a testing ground for our phenomenological approach to the spectral function and probe the influence of momentum distribution and treatment of the mean field spectral function on the differential cross sections. The obtained model reproduces very well results of the exact spectral function of oxygen and can be applied to heavier nuclei, such as calcium or argon.

PACS numbers: 13.15.+g, 25.30.Pt