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Reactions with the methoxy radical CH$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$O$\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ have found to be significant pathways of production and destruction of important interstellar molecules and ions like NH$\mathrm{<mrow\; data-mjx-texclass="ORD">4</mrow><mrow\; data-mjx-texclass="ORD">+</mrow>}$, NH$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$, H$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$O, H$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$O$\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ }. These processes compete with the dissociative recombination of the named ions. Therefore, measurements of the rates, cross-sections and branching ratios of the dissociative recombination of the iosotopomers $CH3O+$ and $CD3O+$ have been perfomed at the CRYRING storage ring located at Stockholm, Sweden. Preliminary evaluation of the data yielded a reaction rate coefficient of $$ cm$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$mol$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$s$$ and $\ 8.4\ast 10^{-7}\left( \frac{T}{300}\right) ^{-0.62}\ $ cm$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$% mol$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$s$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ for $CH3O+$ and $CD3O+,$ respectively. Calculation of the branching ratios rendered the following branching ratios for the reaction channels leading to the fissure of the C-O bond:, $$ $CH2+OH$ \ $(1.6\%);$\ $D2O+CD (2\%),$ $$ \ $(6\%)$ respectively. The rest of the dissociative recombination rates was contributed from channels leaving the C-O bond intact: 92% and 98% for $CH3O+$ and $CD3O+$, respectively. Contrary to the $CH3OH2+$ ion}, the pathways preserving the bond between the heavy atoms dominate.