We report measurements of the carbon monoxide ground state rotational
transition (12C16O J = 1-0) with the Zpectrometer
ultrawideband spectrometer on the 100 m diameter Green Bank Telescope.
The sample comprises 11 galaxies with redshifts between z = 2.1 and 3.5
from a total sample of 24 targets identified by Herschel-ATLAS
photometric colors from the SPIRE instrument. Nine of the CO
measurements are new redshift determinations, substantially adding to
the number of detections of galaxies with rest-frame peak submillimeter
emission near 100 μm. The CO detections confirm the existence of
massive gas reservoirs within these luminous dusty star-forming galaxies
(DSFGs). The CO redshift distribution of the 350 μm selected galaxies
is strikingly similar to the optical redshifts of 850 μm-selected
submillimeter galaxies in 2.1