60th OSU International Symposium on Molecular Spectroscopy TF0360th OSU International Symposium on Molecular Spectroscopy TF03

The millimeter-wave rotational The millimeter-wave rotational spectrum of lactic acidspectrum of lactic acid

Zbigniew Kisiel, Ewa Białkowska-Jaworska,Lech Pszczółkowski

Institute of Physics, Polish Academy of Sciences

Warszawa, Poland

The lactic acid moleculeThe lactic acid moleculeThe lactic acid moleculeThe lactic acid molecule

Borba et. al., PCCP 6, 2101 (2004)

ZPEPopulation

kJ/mol % @ 298K

SsC 0.0 91.7

GskC 8.0 3.6

G’sk’C 8.6 2.9

AaT 10.0 1.6

SsC

GskC

16.4 kJ/mol

Lowest energy vibrational states in lactic acid Lowest energy vibrational states in lactic acid Lowest energy vibrational states in lactic acid Lowest energy vibrational states in lactic acid

30= 60 cm-1

28= 240

29= 224

27= 287

vibrational spectrum: Borba et. al., PCCP 6, 2101 (2004) rotational spectrum: van Eijck, JMS 101, 133 (1983)

Studied in this work, and assigned with confidence

Measured, but only tentative assignment

The Warsaw broadband millimeter-wave spectrometerThe Warsaw broadband millimeter-wave spectrometerThe Warsaw broadband millimeter-wave spectrometerThe Warsaw broadband millimeter-wave spectrometer

The IFPAN The IFPAN MMW MMW spectrometerspectrometer

120-350 GHz120-350 GHz

Istok BWO in electromagnet

Analysis carried out using the Analysis carried out using the AABSAABS software package software packageAnalysis carried out using the Analysis carried out using the AABSAABS software package software package

All recorded spectra (typically 0.5 GHz each) combined into a single continuous spectrum

Spectra and predictions displayed alongside with two previewing programs

Graphical assignment and automated transfer of frequencies and quantum numbers to datafiles

Fitting and predictions with ASFIT/ASROT (H.M.Pickett’s SPFIT/SPCAT can also be used)

AABS = AABS = AAssignment and ssignment and AAnalysis of nalysis of BBroadband roadband SSpectrapectraavailable on the PROSPE webpage:available on the PROSPE webpage:

http://info.ifpan.edu.pl/~kisiel/http://info.ifpan.edu.pl/~kisiel/prospe.htmprospe.htm

http://info.ifpan.edu.pl/~kisiel/http://info.ifpan.edu.pl/~kisiel/prospe.htmprospe.htm

Loomis-Wood type plot for Loomis-Wood type plot for KKa a = 1= 10 transitions0 transitionsLoomis-Wood type plot for Loomis-Wood type plot for KKa a = 1= 10 transitions0 transitionsGround state 30 = 1

a a //bba a //bb

b: 32 8,24 319,23

a: 32 9,24 319,23

a: 32 8,24 318,23

b: 32 9,24 318,23

tot = 2.32 D

tot = 2.34 D

tot = 2.33 D

Spectroscopic constants determined for the ground stateSpectroscopic constants determined for the ground stateSpectroscopic constants determined for the ground stateSpectroscopic constants determined for the ground state

Dataset for the Dataset for the ground stateground state

Dataset for the Dataset for the ground stateground state

MMW: 171-318 GHz

FTMW: 8-16 GHz

CMW: 27-39 GHz

Quartic constants for the ground stateQuartic constants for the ground stateQuartic constants for the ground stateQuartic constants for the ground state

GAMESSGAMESSGAMESSGAMESS FCONVFCONVFCONVFCONV VIBCAVIBCAVIBCAVIBCA

}1.2 %

The The 3030 satellite sequence satellite sequence The The 3030 satellite sequence satellite sequence

? ?

Sixth quantum ?

Observed for transitions with lowest values of Kc , owing to the very

small change in A on excitation of the 3030 mode mode

Changes in constants on excitation of the Changes in constants on excitation of the 3030 mode modeChanges in constants on excitation of the Changes in constants on excitation of the 3030 mode mode

quartics

octicssextics

A,B,C

KJ

C

J

The The 3030 torsional mode torsional mode The The 3030 torsional mode torsional mode

Intramolecular hydrogen bond

30 60 cm-1

GAMESSGAMESSGAMESSGAMESS output displayed with ChemCraftChemCraftChemCraftChemCraft

methyl torsion, 29= 224 cm-1

Assignment of the minor vibrational satellites Assignment of the minor vibrational satellites Assignment of the minor vibrational satellites Assignment of the minor vibrational satellites

Lowest energy vibrational states in lactic acid Lowest energy vibrational states in lactic acid Lowest energy vibrational states in lactic acid Lowest energy vibrational states in lactic acid

30= 60 cm-1

28= 240

29= 224

27= 287 vu ?

Conclusions:Conclusions:Conclusions:Conclusions:

Spectroscopic constants determined for the ground state and nine different vibrational excited states

Strongest features in rotational spectrum can be predicted with confidence well into the submillimeter-wave region

Well-behaved rotational spectrum in lowest states: meaningful quartics in Watson’s Hamiltonian and all transitions fitted to within experimental accuracy

Vibrational states crowded above 200 cm –1 and subject to various perturbations

In progress:In progress:In progress:In progress:

Dipole moment measurement

Search for hydrogen-bonded complexes