The trioxide, CF3OC(O)OOOC(O)OCF3, reacts with NO2 at 0 degrees C to yield the new peroxynitrate, CF3OC(O)OONO2, which is stable for hours at room temperature. It is spectroscopically characterized and some thermal properties are reported. From the vapor pressure, In(p/p(0)) = 14.06 - 4565/T, of the liquid above the melting point of -89 degrees C, the extrapolated boiling point is 52 degrees C. CF3OC(O)OONO2 dissociates at higher temperatures and low pressures into the radicals CF3OC(O)OO and NO2 as demonstrated by matrix isolation experiments. The matrix-isolated peroxy radicals consist in a rotameric mixture of trans, trans, trans-CF3OC(O)OO and trans, trans, cis-CF3OC(O)OO, where trans and cis denote dihedral angles of ca. 180 degrees and 0 degrees, respectively, around beta F-C-O-C, beta C-O-C-O, and beta O-C-O-O, with an equilibrium composition dependent on the thermolysis temperature. The radical trans, trans, cis-CF3OC(O)OO is found to be ca. 3 W mol(-1) higher in enthalpy than trans, trans, trans-CF3OC(O)OO, DFT calculations are performed to support the vibrational assignments and to provide structural information about CF3OC(O)OONO2.