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   61211
   It is important to reconsider the radiative process in an intracluster
   medium, since the optical depth of Fe-K emission lines at the central
   core region is around unity by resonant scattering effect. It causes
   uncertainty of abundance determination by a factor of two at most. Two
   clusters 3C129(z=0.0218) and A3667(z=0.0556) are selected for this
   purpose under criteria of high intensity, temperature of 5-7keV,
   isothermality and large angular size fit well to GIS field of view.
   Additionally 3C129 located in the direction of galactic plane is useful
   to observe the small scale distribution of absorbing gas in our galaxy
   by shadowing effect.
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