Knowledge Bank

The molecules hydroxyacetone and lactonitrile are attractive candidates for astrophysical studies because they exhibit the next level of chemical complexity, yet still remain similar in size to other already identified species. Previous spectroscopic work}} in the early 1980s on these two species proved insufficient for interstellar searches. In each of these early studies, course measurements over a very small frequency range (10 to 40 GHz) made it impossible to accurately predict frequencies useful for astronomical observations. Last year at this conference, Braakman et al.} reported the rotational spectrum of hydroxyacetone at 3 mm and 1 mm wavelengths, but reported that they were having difficulties with the E-state assignment presumably owing to its low-barrier internal rotor. In March 2005, we independently measured the spectrum of hydroxyacetone at 3mm, 2mm and also in the microwave region using our newly constructed Fourier transform microwave spectrometer. The E-state microwave lines led us to several misassignments in the original spectroscopy paper. We now have a global fit of the A- and E-states of hydroxyacetone for J$<$31andK$<$8\; using\; a\; code\; provided\; by\; Isabella\; Kleiner\; for\; internal\; rotors.\; The\; rho-axis\; code\; included\; the\; eigenfunction\; decomposition\; method\; outlined\; in\; Mekhtiev\; and\; Hougen\}\; and\; was\; subsequently\; modified\; with\; the\; second\; diagonalization\; routine\; outlined\; by\; Ilyushin\}.\; We\; are\; currently\; working\; on\; assigning\; the\; first\; torsional\; state.\; Work\; has\; just\; started\; on\; Lactonitrile\; and\; at\; present\; we\; cannot\; located\; the\; ground\; state\; conformer.\; The\; two\; series\; reported\; by\; Corbelli\; and\; Lister\; did\; not\; produce\; lines\; in\; our\; cold\; molecular\; beam\; source;\; hence\; it\; is\; likely\; that\; those\; lines\; are\; from\; some\; excited\; vibrational\; states\; or\; other\; high\; energy\; conformers.\; \%$^1$ Kattija-Ari and Harmony, (1980), Int. J. of Quant. Chem.: Quant. Chem. Symp., 14, 443\ %$2$ Corbelli and Lister, (1981), J. Mol. Struct., 74, 39\ %$3$ Braakman et al., (2005), The 60th International Symposium on Molecular Spectroscopy, RA07\ %$4$ Mekhtiev and Hougen, (1998), J. Mol. Spectr., 187, 49\ %$5$ Ilyushin, (2004), J. Mol. Spect., 227, 140