1995A&A...299..382W

Absorption lines of CO(1-2), CO(2-3), HCO⁺(1-2) and HCN(1-2) have been detected at a redshift of z_a=0.68466 towards the background BLLac object B0218+357. The CO and HCN lines are strongly saturated, while the HCO⁺ line is mildly saturated. Lower limits to the column densities are (7.0±0.3)x10¹⁶/cm² for CO, (7.4±0.2)x10¹³/cm² for HCO⁺ and (1.4±0.1)x10¹⁴/cm² for HCN. The filling factor for the background source is larger than 0.7-0.8. The absorption line profile is asymmetric with a width of ∼30km/s. B0218+357 is a gravitational lens candidate with two compact continuum sources separated by 335mas (1.8kpc). The small linewidth of the molecular absorption puts constraints on the inclination and position angle of the lensing galaxy. We also report a search for QSOs molecular absorption lines in 12 other redshifted systems; none were detected.