Search for particle-bound<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mmultiscripts><mml:mi mathvariant="normal">O</mml:mi><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>26</mml:mn></mml:mrow></mml:mmultiscripts></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mmultiscripts><mml:mi mathvariant="normal">F</mml:mi><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>28</mml:mn></mml:mrow></mml:mmultiscripts></mml:math>in<i>p</i>-stripping reactions

We have searched for particle-bound $^{26}\mathrm{O}$ and $^{28}\mathrm{F}$ isotopes in the reaction products of secondary $^{27}\mathrm{F}$ and $^{29}\mathrm{Ne}$ beams, respectively. No events have been observed. Upper limits of 3.3 mb and 1.2 mb for the respective production cross sections of $^{26}\mathrm{O}$ and $^{28}\mathrm{F}$ by one p-stripping reactions are established. Since in the case of $^{28}\mathrm{F}$, this upper limit is sufficiently small compared to common estimates, we conclude that $^{28}\mathrm{F}$ is most likely unbound. For the case of $^{26}\mathrm{O}$, our result is not statistically significant, thus, the question cannot be answered whether $^{26}\mathrm{O}$ is a particle-unbound nucleus or not.