The Second Torsional State of Acetaldehyde

We have fit to within experimental accuracy a data set for acetaldehyde obtained by combining 1014 v t = 0, 840 v t = 1, and 430 v t = 2 microwave lines with 420 v t = 1 ← 0 and 404 v t = 2 ← 1 far-infrared lines. The principal additions to the previously treated v t = 0 and v t = 1 microwave data set consist of about 250 new measurements from Barclay, Anderson, and Ziurys and 900 new measurements from Nizhny Novgorod; the v t = 2 measurements include about 400 lines from Nizhny Novgorod and a few lines from various other sources. The previously treated v t = 1 ← 0 far-infrared data set was extended by adding about 200 high- J lines from the 1 ← 0 fundamental band and 400 lines from the 2 ← 1 hot band, all taken from a previously reported Fourier transform spectrum. The final fit, which uses a slightly extended model from the literature. requires 48 parameters to achieve an overall unitless weighted standard deviation of 1.06. The present fit includes essentially all available infrared and microwave transitions involving torsional lexels below the top of the internal rotation barrier.