Photon Absorption on a Neutron-Proton Pair in 3He and 4He

We have developed a phenomenological quasi-deuteron model to describe photodisintegration reactions of $^3$He and $^4$He at intermediate photon energies, and compared the results with experimental data obtained by TAGX group in which contributions from photon absorption by $pn$ pair were selectively observed. The data can be reproduced reasonably well, however there still remain certain discrepancies between calculated results and data.