IRAM observations of JVAS/CLASS gravitational lenses

We have searched for molecular absorption lines at millimeter wavelengths in eleven gravitational lens systems discovered in the JVAS/CLASS surveys of flat spectrum radio sources. Spectra of only one source 1030+074 were obtained in the 3-, 2and 1.3-millimeter band at the frequencies corresponding to common molecular transitions of CO and HCO as continuum emission was not found in any of the other sources. We calculated upper limits to the column density in molecular absorption for 1030+074, using an excitation temperature of 15 K, to be NCO < 6.3 × 10 cm−2 and NHCO+ < 1.3 × 10 cm−2, equivalent to hydrogen column density of the order NH < 10 cm−2, assuming standard molecular abundances. We also present the best upper limits of the continuum at the lower frequency for the other 10 gravitational lenses.