The intrinsic decay rate of orthopositronium formed in ${rm SiO_2}$ powder is measured using the direct $2gamma$ correction method such that the time dependence of the pick-off annihilation rate is precisely determined. The decay rate of orthopositronium is found to be $7.0396pm0.0012 (stat.)pm0.0011 (sys.)mu s^{-1}$, which is consistent with our previous measurements with about twice the accuracy. Results agree well with the $O(alpha^2)$ QED prediction, and also with a result reported very recently using nanoporous film.
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