Limits on the abundance and coupling of cosmic axions at 4.5<ma<5.0 μeV

We report preliminary results from a search for galactic axions in the frequency range 1.09<$f_a$<1.22 GHz. For an axion linewidth ${\Gamma }_a$≤200 Hz we obtain the experimental limit ($g_{a\gamma \gamma }$/$m_a$ ${)}^2$ ${\rho }_a$<1.4×${10}^{-41}$. The theoretical prediction is ($g_{a\gamma \gamma }$/$m_a$ ${)}^2$ ${\rho }_a$=3.9×${10}^{-44}$ with ${\rho }_a$=300 MeV/${\mathrm{cm}}^3$. We have also searched for the presence of a continuous spectrum of light pseudoscalar particles; if we assume that the above ${\rho }_a$ is contained between the upper and lower frequencies of our search, then we find that $g_{a\gamma \gamma }$<2×${10}^{\mathrm{-}30}$ ${\mathrm{MeV}}^{1/2}$ ${\mathrm{cm}}^{3/2}$≃${10}^{\mathrm{-}11}$ ${\mathrm{GeV}}^{\mathrm{-}1}$.