gamma. emission probabilities from unbound states in Se-78,Se-80, populated by a neutron-transfer reaction (d,p) on Se-77,Se-79 nuclei in inverse kinematics, were measured by directly detecting reaction residues. Assuming the spin distribution at the respective excitation energy of the unbound state, the cross-sections of the Se-79(n, gamma)Se-80 reaction were evaluated using the gamma emission probabilities. The surrogate-ratio method with the experimental gamma emission probabilities of Se-78,Se-80 was also employed to deduce the cross-sections of Se-79(n, gamma) reaction by incorporating the theoretical evaluations of the neutron-capture reaction on the isomeric state in Se-77. Our two cross-sections are in good agreement with existing nuclear data compilations for the neutron-capture reaction on Se-79. The presented method contributes to the body of existing knowledge by providing approaches for determining the neutron capture cross-sections of radioactive nuclei at various neutron energies.