1. 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

2. 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)

3. Lowest vibrational states in pyruvic acid
this work

4. The Warsaw broadband millimeter-wave spectrometer

5. The mm-wave rotational spectrum of pyruvic acid

6. 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:

8. Loomis-Wood type plots used for assignment…

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

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

11. 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

12. 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, GHz

13. 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)

14. Spectroscopic constants for the ground state of glycolic acid
+ sextics

15. V21 = 0 1 2 3 4 5

16. 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 …