Search for radio recombination lines towards the gravitational lens PKS   1830-211
  A search for radio recombination lines near 20 cm at z=0.193 and z=0.886 towards the gravitational lens system PKS 1830-211 has yielded upper limits on the line optical depth of 5 x 10^{-5} and 5 x10^{-4} at the two redshifts respectively. Based on the non-detections, we derive upper limits to the emission measure of the ionized gas in the absorbing systems. We also present continuum flux density measurements over the frequency range 0.3-45 GHz made at a single epoch. 
Niruj R. Mohan (1,2), K.R. Anantharamaiah (1) and W.M. Goss (3) ((1)   RRI, India (2) IISc, India (3) NRAO, Socorro, USA)