62nd OSU International Symposium on Molecular Spectroscopy WG10 The millimeter-wave rotational spectra of pyruvic acid and of glycolic acid Zbigniew Kisiel, Ewa Białkowska-Jaworska, Lech Pszczółkowski Institute of Physics, Polish Academy of Sciences Warszawa, Poland Steven B. Charnley Space Science and Astrobiology Division, NASA Ames Research Center , CA, USA

The pyruvic acid molecule 10 atoms ma = 2.27(2) D mb = 0.35(2) D n23 n24 Previous investigations (all cm-wave): Kaluza et al., Chem.Phys.Lett. 22, 454 (1973) Marstokk+Mollendal, J.Mol.Struct. 20, 257 (1974) Dyllick-Brenzinger et al., Chem.Phys. 23, 195 (1977) Meyer+Bauder, J.Mol.Spectrosc. 94, 136 (1982)

Lowest vibrational states in pyruvic acid this work

The Warsaw broadband millimeter-wave spectrometer

The mm-wave rotational spectrum of pyruvic acid

AABS = Assignment and Analysis of Broadband Spectra Analysis carried out using the AABS software package All recorded spectra (typically 0.5 GHz each) are combined into a single continuous spectrum Spectra and predictions are displayed alongside with two previewing programs Graphical assignment and automated transfer of frequencies and quantum numbers to datafiles Fitting and predictions with ASFIT/ASROT or H.M.Pickett’s SPFIT/SPCAT AABS = Assignment and Analysis of Broadband Spectra available on the PROSPE webpage: http://info.ifpan.edu.pl/~kisiel/prospe.htm

Loomis-Wood type plots used for assignment…

A-E splitting in the J = 38  37 transition of the g.s.

The data set for the ground, A-symmetry, substate of pyruvic acid 732 fitted lines sfit = 36.9 kHz MMW: 171 - 314 GHz CMW: 27 - 39 GHz FTMW: 10 - 17 GHz

Summary of results obtained for pyruvic acid Analysis of g.s, v24=1,2,3, and v23=1 taken up to 314 GHz Three different fitting programs were used in comparative manner: SPFIT (Pickett) – effective single state fits for A and E states XIAM (Hartwig) – IAM fit of A+E ERHAM (Groner) – effective rotational Hamiltonian, A+E All three programs were found satisfactory for the ground state, but applicability of single state fits quickly diminished with increasing torsional excitation ERHAM was most economic in fitting experimental data (e.g. requiring 27 constants for g.s. A+E to compare with 15+24=39 for single state fits) Results now published: J.Mol.Spectrosc. 241, 220 (2007) where some discussion on how to read and compare the derived constants was also made

9 atoms ma = 1.913(5) D mb = 0.995(14) D The glycolic acid molecule Previous investigations: Blom+Bauder, Chem.Phys.Lett. 82, 492 (1981) – most stable isomer, cmw Hasegawa et al., J.Mol.Struct. 82, 205 (1982) – isotopic work, cmw Godfrey et al., J.Am.Chem.Soc. 119, 2232 (1997) – less stable trans conformer, mmw jet, 48-71 GHz

Lowest vibrational states in glycolic acid Assigned and fitted Assigned, but not yet satisfactorily fitted w 20= 280.6 w 14= 269.5 w 21= 75 cm-1 ?  DFT=65, ir=152, mw Irel=123(15) cm-1 vibrational spectrum: Hollensten et. al., Spectrochim. Acta A 3, 193 (1983)

Spectroscopic constants for the ground state of glycolic acid + sextics

V21 = 0 1 2 3 4 5

Summary of results obtained for glycolic acid Analysis of g.s, v21= 1 and 2 taken up to 317 GHz, Watson’s A-reduced Hamiltonian applicable. v21= 3 and 4, 5 are perturbed. v14= 1 and v20= 1 have been assigned but both also turn out to be perturbed. Multistate fit or fits required to understand the spectrum for vibrational excitation upwards of 250 cm-1 … Rotational transitions of other conformers not yet assigned in the room temperature mmw spectrum – but two such conformers should in principle be visible …