THE LABORATORY SPECTRUM OF ACETALDEHYDE AT 1 MILLIMETER (230-325 GHZ)

The rotational spectrum of acetaldehyde (CH3CHO) in the frequency rang e 230-325 GHz has been measured in the laboratory using millimeter/sub millimeter direct absorption spectroscopy. Over 250 transition frequen cies are presented for this molecule for both A and E symmetry species in its ground (upsilon(t) = 0) and first excited (upsilon(t) = 1) tor sional state, with experimental uncertainties of +/- 50 kHz. The data were fitted with a model involving an internal rotation potential func tion, which typically reproduces the measured frequencies to nu(obs) - nu(calc) less than or similar 50 kHz for both ground and upsilon(t) = 1 state. These newly measured rest frequencies should aid in the iden tification of interstellar CH3CHO and in spectral line assignments for millimeter-band scans.