title: Fourier transform microwave and millimeter wave spectroscopy of quinazoline, quinoxaline, and phthalazine.
abstract: The pure rotational spectra of the bicyclic aromatic nitrogen heterocycle molecules, quinazoline, quinoxaline, and phthalazine, have been recorded and assigned in the region 13-87 GHz. An analysis, guided by ab initio molecular orbital predictions, of frequency-scanned Stark modulated, jet-cooled millimeter wave absorption spectra (48-87 GHz) yielded a preliminary set of rotational and centrifugal distortion constants. Subsequent spectral analysis at higher resolution was carried out with Fourier transform microwave (FT-MW) spectroscopy (13-18 GHz) of a supersonic rotationally cold molecular beam. The high spectral resolution of the FT-MW instrument provided an improved set of rotational and centrifugal distortion constants together with nitrogen quadrupole coupling constants for all three species. Density functional theory calculations at the B3LYP∕6-311+G∗∗ level of theory closely predict rotational constants and are useful in predicting quadrupole coupling constants and dipole moments for such species.
authors.affiliation: School of Chemistry, Monash University, Clayton, Victoria 3800, Australia. donald.mcnaughton@monash.edu
authors.forename: Don
authors.initials: D
authors.lastname: McNaughton
authors.forename: Peter D
authors.initials: PD
authors.lastname: Godfrey
authors.forename: Michaela K
authors.initials: MK
authors.lastname: Jahn
authors.forename: David A
authors.initials: DA
authors.lastname: Dewald
authors.forename: Jens-Uwe
authors.initials: JU
authors.lastname: Grabow