between 2003 November and 2005 May using the 13.7m radome–enclosed Quabbin millimeter wave telescope. The 32 pixel SEQUOIA focal plane array[^2] receiver observed the J = 1$\rightarrow$0 transition of  and simultaneously. Since the receiver uses amplifiers for the first stage, there is no issue of the sideband gain uncertainty and its effect on calibration. Sixteen pixels are arranged in a 4 x 4 array in two orthogonal linear polarizations. The main beam of the antenna pattern had a full width to half maximum angular width of 45for  and 47 for .

The data were obtained using an on–the–fly (OTF) mapping technique. A standard position was observed using position switching several times per observing session to verify calibration consistency. Details of the data–taking, data reduction, and calibration procedures are given by [@narayanan2007]. The signals from a band of frequencies around each spectral line were sent to an autocorrelation spectrometer with 1024 lags covering 25 MHz for each spectral line. The lag spacing of the spectrometer system corresponds to 0.068  for  and 0.065  for . The data cube of each isotopologue employed in the subsequent analysis included 76 spectral channels for  and 80 channels for  covering approximately -5  to +14.9 and thus 