Detecting SQUARE_BRACKET_OPENCIISQUARE_BRACKET_CLOSE emission in zvirgul2.3 lensed SMGs from the South Pole Telescope survey

With ALMA cycle 0 time we have observed 26 sources selected from the South Pole Telescope (SPT) survey, which covers 2500 deg^2 of sky area. These SPT sources are strongly lensed and the sample includes two of the most distant submm galaxies at z5.7. The results of these observations reveal an unbiased redshift distribution of our sources peaking at zvirgul 3.5.We have started a followup started to observe the CII line in these sources. Combined with lowJ CO lines we have already found tentative evidence for evolutionary effects in the ISM properties of our sources. We here propose to observe three SPT sources at 2<z<2.5 which can only be observed with SPIRE/FTS to obtain critical observations in this redshift range, on the lowz side of our redshift distribution. This is our last chance to probe this redshift range in our sample, which is complete at 3<z<5.7. The predicted CII fluxes of our three targets are brighter than published results, ensuring the succes of this proposal and the legacy of Herschel in this field. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]