Thanks to its high spectral resolution (~5 eV at 6 keV), the Soft X-ray<br />
Spectrometer (SXS) on board Hitomi enables us to measure the detailed structure<br />
of spatially resolved emission lines from highly ionized ions in galaxy<br />
clusters for the first time. In this series of papers, using the SXS we have<br />
measured the velocities of gas motions, metallicities and the multi-temperature<br />
structure of the gas in the core of the Perseus cluster. Here, we show that<br />
when inferring physical properties from line emissivities in systems like<br />
Perseus, the resonant scattering (RS) effect should be taken into account. In<br />
the Hitomi waveband, RS mostly affects the FeXXV He$\alpha$ line ($w$) - the<br />
strongest line in the spectrum. The flux measured by Hitomi in this line is<br />
suppressed by a factor ~1.3 in the inner ~30 kpc, compared to predictions for<br />
an optically thin plasma; the suppression decreases with the distance from the<br />
center. The $w$ line also appears slightly broader than other lines from the<br />
same ion. The observed distortions of the $w$ line flux, shape and distance<br />
dependence are all consistent with the expected effect of the resonant<br />
scattering in the Perseus core. By measuring the ratio of fluxes in optically<br />
thick ($w$) and thin (FeXXV forbidden, He$\beta$, Ly$\alpha$) lines, and<br />
comparing these ratios with predictions from Monte Carlo radiative transfer<br />
simulations, the velocities of gas motions have been obtained. The results are<br />
consistent with the direct measurements of gas velocities from line broadening<br />
described elsewhere in this series, although the systematic and statistical<br />
uncertainties remain significant. Further improvements in the predictions of<br />
line emissivities in plasma models, and deeper observations with future X-ray<br />
missions will enable RS measurements to provide powerful constraints on the<br />
amplitude and anisotropy of clusters gas motions.