Low-energy upbend in the photon strength function of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Fe</mml:mi><mml:mprescripts/><mml:none/><mml:mn>57</mml:mn></mml:mmultiscripts></mml:math>

In this work, we investigate the photon strength function (PSF) of $^{57}\mathrm{Fe}$ derived from thermal neutron capture on $^{56}\mathrm{Fe}$, with a focus on the low-energy photon strength below the neutron separation energy. We show that the PSF derived from primary $\ensuremath{\gamma}$ transitions does not support the significant low-energy enhancement previously reported in the Oslo method. The role of secondary $\ensuremath{\gamma}$ transitions and $E2$ transitions in the total PSF is discussed. Averaging the $E2$ primary transitions following thermal neutron capture on $^{56}\mathrm{Fe}$, we obtained an estimate for the E2 strength function for primary gamma transitions in radiative capture, ${f}_{E2}=2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}\phantom{\rule{4pt}{0ex}}{\mathrm{MeV}}^{\ensuremath{-}5}$.

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