Search for particle-bound $^{26}$O and $^{28}$F in $p$-stripping

We have searched for particle-bound $^{26}$O and $^{28}$F isotopes in the reaction products of secondary $^{27}$F and $^{29}$Ne beams, respectively. No events have been observed. Upper limits for the respective production cross sections by one-$p$-stripping reactions are established under the assumption that $^{26}$O and $^{28}$F are particle bound. Since the experimental upper limits are much lower than common estimates we conclude that neither $^{26}$O nor $^{28}$F are likely particle bound.