Microwave Spectrum Of Acetic Acid: The Third And Fourth Excited Torsional States

We present the first study of the millimeter and submillimeter wave spectra of the third and fourth excited torsional states of acetic acid (\chem{CH_3COOH}). New measurements have been carried out in the 149-183 GHz and 255-420 GHz ranges using the millimeter wave spectrometer in the Institute of Radio Astronomy of NASU (Ukraine). Already published data [1] were combined with the new measurements and fitted using the rho-axis-method torsion–rotation Hamiltonian and RAM36 code [2]. The current fit uses 109 parameters to give an overall weighted root-mean-square deviation of 2.1 for the dataset consisting of 34799 transitions (which due to blending correspond to 21773 measured line frequencies), among which 2663 and 1243 transitions correspond to the third and fourth excited torsional states of \chem{CH_3COOH}, respectively. The new dataset also contains numerous intertorsional transitions (2407) including those involving energy levels from the third and fourth torsional excited states that are observed due to intensity borrowing via avoided crossing interactions that provide a direct measure of torsional energy spacings associated with torsional potential barrier. In the talk the details of the experimental dataset and analysis will be given\footnote{This work was done under support of the Volkswagen foundation. The assistance of Science and Technology Center in Ukraine is acknowledged (STCU partner project P756).}. [1] V. V. Ilyushin, C. P. Endres, F. Lewen, S. Schlemmer, B. J. Drouin J. Mol. Spectrosc. 290, pp. 31 - 41, 2013. [2] V. Ilyushin, Z. Kisiel, L. Pszczółkowski, H. Mäder, J. T. Hougen, J. Mol. Spectrosc. 259, pp. 26-38, 2010

Millimeter wave spectrum of nitromethane

A new study of the millimeter wave spectrum of nitromethane \chem{CH_3NO_2} is reported. The new measurements covering the frequency range from 49 GHz to 236 GHz have been carried out using spectrometer in IRA NASU (Ukraine). The transitions belonging to the m $\leq$ 8 torsional states have been analyzed using the RAM36 program\footnote{V. Ilyushin, Z. Kisiel, L. Pszczółkowski, H. Mäder, J. T. Hougen J. Mol. Spectrosc. 259 (2010) 26-38.}, which has been modified for this study to take into account the quadrupole hyperfine structure due to presence of the nitrogen atom. The dataset consisting of 5838 microwave line frequencies and including transitions with {\it J} up to 50 was fit using a model consisting of 93 parameters and weighted root-mean-square deviation of 0.89 has been achieved. In the talk the details of this new study will be discussed

VIBRATION-TORSION-ROTATION INTERACTIONS IN MOLECULES WITH A C3v TOP AND Cs FRAME: vt=3,4 TORSIONAL AND C–S STRETCHING VIBRATIONAL STATES OF METHYL MERCAPTAN CH3SH

We present\footnote{This work was done under support of the Volkswagen foundation. The assistance of Science and Technology Center in Ukraine is acknowledged (STCU partner project P686). The work in K{\"o}ln was supported by the Deutsche Forschungsgemeinschaft (DFG) via SFB~956, project B3, and the Ger{\"a}tezentrum Cologne Terahertz Center.} the results of our analysis of the FIR and microwave spectra of the \nub{8} vibrational state (C-S stretch) of methyl mercaptan \chem{CH_3SH} near 710 \wn. The analysis employs a new program which was recently developed for fitting several isolated small-amplitude fundamentals embedded in a pure torsional bath in molecules like methyl mercaptan, in which the frame has C$_{s}$ symmetry and the methyl top has C$_{3v}$ symmetry. Our study involves the energy levels that belong to the \nub{8} vibrational state itself as well as to v$_t$ = 0, 1, 2, 3, 4 torsional vibrational states of methyl mercaptan. In our analysis we used data available in the literature [1,2,3] as well as the results of the new measurements from Kharkiv, K{\"o}ln, and Braunschweig. In the talk the details of this new study will be discussed. [1] L.-H. Xu, R. M. Lees, G. T. Crabbe, et al., J. Chem. Phys. 137, 104313 (2012). [2] R.M. Lees, Li-Hong Xu, B.E. Billinghurst, J. Mol. Spectrosc. 352, 30-38 (2016). [3] R.M. Lees, Li-Hong Xu, B.E. Billinghurst, J. Mol. Spectrosc. 319, 45-56 (2018)

ISOLATED SMALL-AMPLITUDE FUNDAMENTALS EMBEDDED IN A PURE TORSIONAL BATH: FIR AND MW SPECTRA OF THE ν10 VIBRATIONAL MODE AND HOT TORSIONAL BANDS OF ACETALDEHYDE

We present\footnote{This talk is dedicated to the memory of Dr. Jon T. Hougen (who recently passed away) in recognition of his essential contribution to this project.} the results of achieved progress in our analysis of the far-IR and microwave spectra of the \nub{10} vibrational state of acetaldehyde\footnote{This work was done under support of the Volkswagen foundation. The assistance of STCU is acknowledged (partner project P686).}. The analysis of the gs - \nub{10} band near 509 \wn involves the energy levels that belong to the v$_t$ =0, 1 torsional states of \nub{10} vibrational mode as well as v$_t$ =0, 1, 2, 3, 4 torsional states of the ground vibrational state. The intervibrational interactions between \nub{10} vibrational state and torsional bath is taken explicitly into account with the help of a new program which was recently developed for fitting several isolated small-amplitude fundamentals embedded in a pure torsional bath in molecules with C$_{s}$ frame and C$_{3v}$ top. Obtained results provide significant progress in comparison with the previous fitting attempts for gs - \nub{10} band of acetaldehyde near 509 \wn. In the talk the details of the results with emphasis on the remaining fitting problems for the hot torsional bands\footnote{The authors are indebted to Dr. A.R.W. McKellar for providing raw spectrum data on torsional bands of acetaldehyde from previous study.} of acetaldehyde will be discussed

The torsional fundamental band and rotational spectra up to 940 GHz of the ground, first and second excited torsional states of acetone

A new global study of the acetone \chem{(CH_3)_2CO} spectrum is reported. The new microwave measurements covering the frequency range from 34 GHz to 940 GHz have been carried out using spectrometers in IRA NASU (Ukraine) and PhLAM Lille (France). The far infrared spectrum of acetone has been recorded on the AILES beamline of the synchrotron SOLEIL using a Fourier transform infrared spectrometer coupled to a long path cell. The transitions belonging to the three lowest torsional states as well as to the observed fundamental band associated with the methyl-top torsion mode (\nub{17} = 1) have been analyzed using recently developed model for the molecules with two equivalent methyl rotors and C$_{2v}$ symmetry at equilibrium (PAM\_C2v\_2tops program)\footnote{ V. Ilyushin, J.T. Hougen J. Mol. Spectrosc. 289 (2013) 41-49.}. The dataset consisting of more than 26100 microwave and 1100 FIR line frequencies and including transitions with {\it J} up to 89 was fit using a model consisting of 119 parameters and weighted root-mean-square deviation of 0.89 has been achieved. In the talk the details of this new study will be discussed

VIBRATION-TORSION-ROTATION INTERACTIONS IN METHYL MERCAPTAN CH3SH: vt=3,4 TORSIONAL, C–S STRETCHING, AND CSH BENDING VIBRATIONAL STATES.

We present\footnote{This work was done under support of the Volkswagen foundation. The assistance of Science and Technology Center in Ukraine is acknowledged (STCU partner project P686a).} the results of a joint analysis of the MIR, FIR, and microwave spectra of the \nub{8} vibrational state (C-S stretch) near 710 \wn, the \nub{7} vibrational state (CSH bend) near 802 \wn, and torsional stack of levels up to fourth excited torsinal state of methyl mercaptan \chem{CH_3SH}. The analysis employs a new program which was recently developed for fitting several isolated small-amplitude fundamentals embedded in a pure torsional bath in molecules like methyl mercaptan, in which the frame has C$_{s}$ symmetry and the methyl top has C$_{3v}$ symmetry. This is the first attempt to perform an analysis of two small amplitude vibrations interacting with torsional bath of states and each other in a molecule with torsional large amplitude motion with this new program. The analysis gave us an opportunity to assign for the first time the pure rotational (microwave) transitions of the \nub{7} vibrational state (CSH bend). In our analysis we used data available in the literature [1,2,3] as well as the results of the new measurements from Kharkiv, K{\"o}ln, and Braunschweig. In the talk the details of this new study will be discussed. [1] L.-H. Xu, R. M. Lees, G. T. Crabbe, et al., J. Chem. Phys. 137, 104313 (2012). [2] R.M. Lees, Li-Hong Xu, B.E. Billinghurst, J. Mol. Spectrosc. 352, 30-38 (2016). [3] R.M. Lees, Li-Hong Xu, B.E. Billinghurst, J. Mol. Spectrosc. 319, 45-56 (2018)

MICROWAVE AND FIR SPECTROSCOPY OF DIMETHYLSULFIDE IN THE GROUND, FIRST AND SECOND EXCITED TORSIONAL STATES

A new study footnote{ This work was done under support of the Volkswagen foundation. The assistance of Science and Technology Center in Ukraine is acknowledged (STCU partner project P686).} of the dimethylsulfide ((CH$_{3}$)$_{2}$S) spectrum is reported. The new measurements have been carried out using the Kharkiv spectrometer in the Institute of Radio Astronomy of NASU (Ukraine) and using the Lille spectrometer in the PhLAM laboratory (France). The new millimeter and submillimeter wave measurements cover the frequency range from 49 GHz to 660 GHz. The rotational transitions belonging to the three lowest torsional states of the molecule as well as the new assignments in the FIR torsional band (AILES beamline of the synchrotron SOLEIL) and the microwave data available in the literature footnote{ A. Jabri, V. Van, H. V. L. Nguyen, H. Mouhib, F. Kwabia Tchana , L. Manceron , W. Stahl, I. Kleiner, A&A 589, A127 (2016).} have been analyzed using recently developed model for the molecules with two equivalent methyl rotors and C$_{2v}$ symmetry at equilibrium (PAM_C2v_2tops program)footnote{ Ilyushin V. V., Hougen J. T. J. Mol. Spectrosc. 289 (2013) 41-49.}. In the talk the details of this new study will be discussed

ADVANCES IN GLOBAL MODELLING OF METHYL MERCAPTAN CH332SH TORSION-ROTATION SPECTRUM

A progress in the analysis of the methyl mercaptan CH$_{3}$SH spectrum in its ground, first and second excited torsional states is reported footnote{ This work was done under support of the Volkswagen foundation. The assistance of Science and Technology Center in Ukraine is acknowledged (STCU partner project P686).}. The available in the literature data footnote{ L.-H. Xu, R. M. Lees, G. T. Crabbe, J. A. Myshrall, H. S. P. Müller, C. P. Endres, O. Baum, F. Lewen, S. Schlemmer, K. M. Menten, and B. E. Billinghurst J. Chem. Phys. 137, 104313 (2012).} were reanalyzed using RAM36 code footnote{ V. Ilyushin, Z. Kisiel, L. Pszczółkowski, H. Mäder, J. T. Hougen // J. Mol. Spectrosc. Vol. 259, pp. 26-38 (2010). } with the main improvement achieved for the root mean square deviation of the microwave data. The updated Hamiltonian model was applied to the further assignments of the methyl mercaptan spectrum using the records obtained in the THz region in the previous study$^{b}$ . Also a new measurement campaign in subTHz frequency range is planned for the nearest future using a set of spectrometers available in Köln. In the talk the details of this new study will be discussed

A NEW MULTI-STATE VIBRATION-TORSION-ROTATION FITTING PROGRAM FOR MOLECULES WITH A C3v TOP AND Cs FRAME: APPLICATION TO THE ν10 BAND OF ACETALDEHYDE

A new program is described for fitting several isolated small-amplitude fundamentals embedded in a pure torsional bath in molecules like acetaldehyde, in which the frame has C$_{s}$ symmetry and the methyl top has C$_{3v}$ symmetry. The program is based on the Longuet-Higgins group theoretical ideas and uses the Rho-axis method. In the talk the basic ideas, the structure of the program as well as the strategy for checking the program will be discussed. Also we present the first results \footnote{ This work was done under support of the Volkswagen foundation. The assistance of Science and Technology Center in Ukraine is acknowledged (STCU partner project P686).} of application of the new program to the spectrum of the \nub{10} vibrational state of acetaldehyde, \chem{CH_3CHO}, near 509 \wn. The analysis of the 509 \wn band is accompanied by the analysis of microwave spectrum of the \nub{10} vibrational state and v$_{t}$ = 3,4 torsional states of acetaldehyde

Invariant Sets and Explicit Solutions to a Third-Order Model for the Shearless Stratified Turbulent Flow

We study dynamics of the shearless stratified turbulent flows. Using the method of differential constraints we find a class of explicit solutions to the problem under consideration and establish that the differential constraint obtained coincides with the well-known Zeman--Lumley model for stratified flows.Comment: arxiv version is already officia