1997A&A...317..907S

We report the detection of the CH ²Π_1/2, J=1/2 ground-state hyperfine transitions at 3.3 GHz in the inter-mediate-velocity cloud G90+39(Draco). The lines were measured with the Effelsberg 100m radio telescope and their main-line strength varies between T_MB≃0.04-0.06K. The emission is found to be optically thin and the derived CH column density ranges between (1-4)x10¹³cm^–2. The CH column density as well as the derived dust-to-gas ratio indicate that the Draco cloud resembles the translucent high-latitude clouds at local velocities. The measurements are used to calculate the molecular hydrogen column density using the theoretically determined linear relation between N(CH) and N(H₂). We find N(H₂)≃4x10²⁰-1x10²¹cm^–2. These values are about a factor five higher than the ones found via the empirical CO/H₂ conversion ratio of Herbstmeier et al. (1993A&A...272..514H).