Celik, G.Celik, E.Kilic, H. S.2020-03-262020-03-2620081434-60601434-6079https://dx.doi.org/10.1140/epjd/e2008-00233-9https://hdl.handle.net/20.500.12395/22232The two-photon excitation cross-section of atomic hydrogen is calculated using explicit summation over intermediate states within the framework of dipole approximation. The matrix element for two-photon excitation is transformed into finite sums, consisting of the product of a radial and angular part. Nine intermediate states are employed in the calculation of the transition matrix element. The two-photon excitation cross-section obtained for the transition 1s(2)S(1/2)-2s(2)S(1/2) in atomic hydrogen is a good agreement with the literature.en10.1140/epjd/e2008-00233-9info:eu-repo/semantics/closedAccessArticle503237240Q3WOS:000262653400002Q3