Mixing Synchrotron Radiation And Laser Sources: Dual-comb Spectroscopy In The Submillimeter-wave Region

On the AILES beamline of the SOLEIL synchrotron, the HEROES consortium is currently developing new spectrometers based on heterodyne mixing of the THz synchrotron radiation with dedicated laser sources. We report here the first results on one of these spectrometers that aims at exploiting the discrete nature of coherent synchrotron radiation (CSR) in the 100--1000 GHz region, revealed a few years ago by our team\footnote{Tammaro, S., Pirali, O., Roy, P., Lampin, J.F., Ducournau, G., Cuisset, A., Hindle, F., Mouret, G. "High density terahertz frequency comb produced by coherent synchrotron radiation" Nature Communications., 6: art. 7733. (2015)}, to perform dual-comb THz spectroscopy. CSR generated by the so called low-$\alpha$ mode of the SOLEIL machine produces a relatively intense, offset-free, high density frequency-comb in the THz range (THz-FC). We will present the details of our preliminary experimental set-up mixing the THz-FC from SOLEIL with an optical comb from Menlo C-fiber femtosecond laser. Pure rotation absorption transitions of acetonitrile in the frequency domain (covering the 100--500 GHz range) as well as time-domain free induction decays (FIDs) were observed allowing to establish the performances of this new instrument

PROGRESS AROUND THE HIGH RESOLUTION HETERODYNE SPECTROMETER OF THE AILES BEAMLINE

Our consortium\footnote{ANR "HEROES: HEterodyne Receivers OptimizEd for Synchrotron sources", Grant number 16-CE30-0020-03} is currently developing a new spectrometer on the AILES beamline of the SOLEIL synchrotron facility to achieve sub-MHz resolution in the THz and far-IR regions. This spectrometer is based on heterodyne mixing of the far-IR synchrotron radiation with various local oscillators (LOs). In past years, we used a frequency multiplication chain to provide LO frequencies which enabled both a deep characterization of the spectral composition of the synchrotron emission\footnote{Tammaro, S., Pirali, O., Roy, P., Lampin, J.F., Ducournau, G., Cuisset, A., Hindle, F., Mouret, G. "High density terahertz frequency comb produced by coherent synchrotron radiation" Nature Communications, 6, 7733 (2015)} and the recording of its first Doppler limited absorption lines (of D$_2$O)\footnote{talk WI02, ISMS 2018}. We recently improved our set-up and measured absorption lines using a far-IR molecular laser pumped by a 10 $\mu$m QCL as the LO. The principle of the spectrometer, together with the first experimental results, will be presented in the talk

Chemical synthesis and high resolution spectroscopic characterization of 1-aza-adamantane-4-one c9h13no from the microwave to the infrared

\begin{wrapfigure}{l}{0pt} \includegraphics[width=5.5cm]{AzaAdamantanone.eps} %\caption{Calculated structure} \end{wrapfigure} We have synthesized 1-aza-adamantane-4-one (C$_9$H$_{13}$NO) starting from commercial 1,4-cyclohexanedionemonoethylene acetal and tosylmethylisocianide and following a procedure described in details in the literature.\footnote{Black, R. M. Synthesis, 1981, 829} The high degree of sample purity was demonstrated by gas chromatography and mass spectrometric measurements, and its structure evidenced by 1H and 13C NMR spectroscopy. We present a thorough spectroscopic characterization of this molecule by gas phase vibrational and rotational spectroscopy. Accurate vibrational frequencies have been determined by infrared and far-infrared spectra. The pure rotational spectrum of the molecule has been recorded both by cavity-based Fourier-transform microwave spectroscopy in the 2-20 GHz region, by supersonically expanding the vapor pressure of the warm sample, and by room-temperature absorption spectroscopy in the 140-220 GHz range. Quantum-chemical calculations have enabled a fast analysis of the spectra. Accurate sets of rotational and centrifugal distorsion parameters of 1-aza-adamantane-4-one in its ground state and five vibrationally excited states have been derived from these measurements

FOURIER TRANSFORM ABSORPTION SPECTROSCOPY OF C3 IN THE ν3 ANTISYMMETRIC STRETCH MODE REGION

The C$_3$ molecule has been detected in a variety of astrophysical objects thanks to the well-known 4050 AA~(A$^1Pi_u$--X$^1Sigma ^+ _g$) electronic transition as well as the two IR active modes of the electronic ground state: $nu_2$ ($sim$ 63.42 cm$^{-1}$) and $nu_3$ ($sim$ 2040.02 cm$^{-1}$)footnote{L. Gausset, G. Herzberg, A. Lagerqvist, B. Rosen, Astrophysical Journal, 45--81 (1965); T. F. Giesen et al., The Astrophysical Journal, 551, L181--L184 (2001); K. W. Hinkle, J. J. Keady, P. F. Bernath, Science, 241, 1319--1322 (1988)}. Previous laboratory data in the $nu_3$ region, obtained using diode laser spectroscopy and the photolysis of allene to produce C$_3$, permitted measurement of the fundamental (0,0,1)$Sigma$--(0,0,0)$Sigma$ as well as the hot bands: (0,1,1)$Pi$--(0,1,0)$Pi$; (0,2,1)$Sigma$--(0,2,0)$Sigma$; (0,2,1)$Delta$--(0,2,0)$Delta$ and provided insights on the anharmonicity of the (0,$nnu_2$,1) vibrational patternfootnote{K. Kawaguchi et al., J. Chem. Phys., 91, 1953--1957 (1989)}._x000d_ _x000d_ We have recorded the absorption spectrum of C$_3$ in the 1800--2100 cm$^{-1}$ region (at a resolution of 0.003 cm$^{-1}$) using the Bruker IFS 125 Fourier Transform spectrometer at the AILES beamline of Synchrotron SOLEIL. C$_3$ was produced in a DC discharge of methane heavily diluted in helium. The rovibrational temperature of C$_3$ produced in our discharge is noticeably higher than in Ref. [4], which allowed us to extend measurements to higher $J$ values. More interestingly, we assigned new hot bands involving higher quanta of the $nu_2$ bending states: (0,$nnu_2$,1) with $n$ ranging from 0 to 5. Despite the absence of $Q$ branches for these bands, which results in a possible ambiguous $J$-assignment of $P$ and $R$ lines, the large variety of data considered in this work, in addition to our experimental data and including observations of comet spectra, allows confident assignments

THZ HETERODYNE SPECTROSCOPY ON THE AILES BEAMLINE OF SOLEIL FACILITY USING THE SYNCHROTRON RADIATION EMITTED BY THE MULTIBUNCH OPERATION MODE

The goal of our project is to develop a new high-resolution spectrometer on the AILES beamline of synchrotron SOLEIL. The spectrometer will record absorption spectra in the 1--5 THz range with sub-MHz resolution using a heterodyne detection scheme. We recently performed a test experiment using the far-IR continuum produced by synchrotron radiation in the multibunch mode, a multiplication chain as local oscillator, and a hot electron bolometer (HEB) as heterodyne mixer. The set-up allowed the detection of one D$_2$O absorption line centered at about 782 GHz ($^R$Q(4)$_{0,4}$) with a resolution better than 1 MHz. We will present the details of the experiment and some instrumental developments in progress

Conformational Landscape of Oxygen-Containing Naphthalene Derivatives

Polycyclic aromatic compounds (PACs) constitute an important class of molecules found in various environments and are considered important pollutants of the Earth's atmosphere. In particular, functionalization of PACs modify the ring aromaticity, which greatly influences the chemical reactivity of these species. In this work we studied several oxygen-containing PACs, relevant to atmospheric chemistry. We investigated the conformational landscape of four naphthalene-derivative molecules -- namely ,1- and 2-hydroxynaphthalene and 1- and 2-naphthaldehyde -- by means of rotational and vibrational spectroscopy supported by quantum chemical calculations. For 1-hydroxynaphthalene and 1-naphthaldehyde, intramolecular hydrogen bonding and steric effects drive the conformational preferences while for 2-hydroxynaphthalene and 2-naphthaldehyde, the charge distributions allow us to understand the conformational landscape. This work not only demonstrates how the localization of the substitution group in the ring influences the conformational relative energies and but also constitutes a step toward a better understanding of the different chemical reactivity of such functionalized PACs

A rotational and vibrational investigation of phenylpropiolonitrile (C6_6H5_5C3_3N)

The evidence for benzonitrile (C$_6$H$_5$CN}) in the starless cloud core TMC-1 makes high-resolution studies of other aromatic nitriles and their ring-chain derivatives especially timely. One such species is phenylpropiolonitrile (3-phenyl-2-propynenitrile, C$_6$H$_5$C$_3$N), whose spectroscopic characterization is reported here for the first time. The low resolution (0.5 cm$^{-1}$) vibrational spectrum of C$_6$H$_5$C$_3$N} has been recorded at far- and mid-infrared wavelengths (50 - 3500 cm$^{-1}$) using a Fourier Transform interferometer, allowing for the assignment of band centers of 14 fundamental vibrational bands. The pure rotational spectrum of the species has been investigated using a chirped-pulse Fourier transform microwave (FTMW) spectrometer (6 - 18 GHz), a cavity enhanced FTMW instrument (6 - 20 GHz), and a millimeter-wave one (75 - 100 GHz, 140 - 214 GHz). Through the assignment of more than 6200 lines, accurate ground state spectroscopic constants (rotational, centrifugal distortion up to octics, and nuclear quadrupole hyperfine constants) have been derived from our measurements, with a plausible prediction of the weaker bands through calculations. Interstellar searches for this highly polar species can now be undertaken with confidence since the astronomically most interesting radio lines have either been measured or can be calculated to very high accuracy below 300 GHz.Comment: 7 figures, 4 tables. Accepted for publication in J. Mol. Spe

High Resolution Spectroscopy Of The Two Lowest Vibrational States Of Quinoline C9h7n

PAHs molecules and derivatives have long been suspected to be present in different objects of the universe but no unambiguous detection (based on rotationally resolved spectroscopy) has been reported yet. Pure rotation transitions in the ground state (GS) of quinoline (which belongs to the C$_{s}$ point group) have been analyzed in a previous work of Kisiel et al.\footnote{Z. Kisiel, O. Desyatnyk, L. Pszczolkowski, S. B. Charnley and P. Ehrenfreund, J. Mol. Spectrosc. 217, 115 (2003)} using micro-wave and sub-mm techniques. We will present in this talk a collective effort to record and assign the rotational structure of the two lowest vibrational states of quinoline (namely \nub{45} and \nub{44} centered at about 168.5 \wn~and 177.6 \wn~respectively). In this study, high resolution synchrotron based FT-FIR together with pure rotation spectroscopy in the sub-mm range permitted to obtain very complementary data. The spectral analysis permitted to identify relatively large perturbation patterns across a K$_{a}$ difference of 2 between the two excited states (both states are A'' symmetry). Successful treatment of the perturbations allowed for the accurate determination of i) the rotational constants in the excited states ii) the Fermi and Coriolis perturbation terms and iii) the relative energies of \nub{45} and \nub{44} to the GS. Since most of the PAHs molecules possess low frequency out of plane vibrations which are relatively close in energy, this study emphasizes the difficulties encountered to simulate accurately the rotational structures of such large molecules in excited vibrational states

THZ HETERODYNE SPECTROSCOPY ON THE AILES BEAMLINE OF SOLEIL FACILITY USING THE SYNCHROTRON RADIATION EMITTED BY THE MULTIBUNCH OPERATION MODE

The goal of our project is to develop a new high-resolution spectrometer on the AILES beamline of synchrotron SOLEIL. The spectrometer will record absorption spectra in the 1--5 THz range with sub-MHz resolution using a heterodyne detection scheme. We recently performed a test experiment using the far-IR continuum produced by synchrotron radiation in the multibunch mode, a multiplication chain as local oscillator, and a hot electron bolometer (HEB) as heterodyne mixer. The set-up allowed the detection of one D$_2$O absorption line centered at about 782 GHz ($^R$Q(4)$_{0,4}$) with a resolution better than 1 MHz. We will present the details of the experiment and some instrumental developments in progress

Spectroscopie par transformée de Fourier dans l'infrarouge lointain

Le travail que je présente est une étude prospective de spectroscopie moléculaire effectuée dans le domaine de l'infrarouge lointain (30-500 cm-1) jusqu alors très peu étudié en spectroscopie par transformation de Fourier. La mise au point au laboratoire de plusieurs dispositifs expérimentaux a permis d enregistrer les spectres d espèces moléculaires (à l état gazeux) d intérêts atmosphérique et astrophysique. Les spectres d absorption et d émission à haute résolution de molécules légères (cis- trans-HONO, H2O, NH3) obtenus par ces dispositifs apportent de nombreuses informations spectroscopiques. Une partie du manuscrit est consacrée à la présentation de ces spectres ainsi qu' à l analyse rotationnelle des espèces moléculaires responsables des structures observées. Par la suite, nous avons enregistré les spectres d'émission dans l'infrarouge lointain de six petites molécules Hydrocarbures Aromatiques Polycycliques (PAHs) ainsi que le spectre d'absorption à température ambiante du naphtalène. Ces spectres sont d'un grand intérêt pour les futurs projets astrophysiques. Finalement, une partie de mon travail a été consacrée à la caractérisation expérimentale de la ligne d extraction du rayonnement synchrotron infrarouge et infrarouge lointain (SIRLOIN-2 au LURE) et à l'utilisation de ce nouveau continuum lumineux pour l'enregistrement de spectres d'absorption à haute résolution.This work deals with a prospective study of far-infrared molecular spectroscopy wich is so far rarely studied by means of Fourier transform spectroscopy. The optimisation of many experimental set-up leads to record the gas phase spectra of atmospherical and astrophysical relevant molecules. The high resolution absorption and emission spectra of light molecules (cis- trans-HONO, H2O, NH3) obtained by these experiments produce numbers of spectroscopic information. A part of the manuscript is devoted to the presentation of the spectra with the rotational analysis of the molecular species responsible of the observed structures.We recorded the far-infrared emission spectra of six small Polycyclic Aromatic Hydrocarbons (PAHs) compounds as well as the room-temperature absorption spectrum of naphtalene. These spectra have an important interest for the future astrophysical observations.A part of my work is devoted to the experimental caracterisation of the infrared and far-infrared synchrotron radiation beamline (SIRLOIN-2, LURE) and the use of this new continuum source for recording the high resolution absorption spectra.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF