Sub-barrier photo-induced fission in ${}^{236}\mathrm{U}(\gamma ,f)$ is investigated within the nonequilibrium Green's function method. A model space for the fission process is constructed by superposing Skyrme-Hartree-Fock wave functions along the fission path allowing the particle-hole excitation. Then, the transition from the photoabsorption channel to the fission channel is described by the nonequilibrium Green's function formalism. The calculated fission cross section in the incident gamma-ray energy range $5\mathrm{MeV}\le E_{\gamma }\le 6\mathrm{MeV}$ reproduces the overall behavior of the experimental data, including the suppression below the fission barrier. An eigenchannel analysis of the wave propagation in the present fission model space is also performed, and the first eigenchannel is found to dominate the fission probability. This result supports the Bohr-Wheeler transition-state picture from a microscopic viewpoint.

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• Fission
• Photonuclear reactions
• Nuclear density functional theory
• Nuclear many-body theory