Transferring calibration from CO2 laser lines to far infrared water lines with the aid of the ν2 band of OCS and the ν2, ν1−ν2, and ν1+ν2 bands of 13CS2: Molecular constants of 13CS2

Polycyclic aromatic hydrocarbons (PAHs) molecules are suspected to be present in the interstellar medium and to participate to the broad and unresolved emissions features, the so-called unidentified infrared bands. In the laboratory, very few studies report the rotationally resolved structure of such important class of molecules. In the present work, both experimental and theoretical approaches provide the first accurate determination of the rotational energy levels of two diazanaphthalene: [1,5]- and [1,6]-naphthyridine. [1,6]-naphthyridine has been studied at high resolution, in the microwave (MW) region using a Fourier transform microwave spectrometer and in the far-infrared (FIR) region using synchrotron-based Fourier transform spectroscopy. The very accurate set of ground state (GS) constants deduced from the analysis of the MW spectrum allowed the analysis of the most intense modes in the FIR (ν38-GS centered at about 483 cm(-1) and ν34-GS centered at about 842 cm(-1)). In contrast with [1,6]-naphthyridine, pure rotation spectroscopy of [1,5]-naphthyridine cannot be performed for symmetry reasons so the combined study of the two intense FIR modes (ν22-GS centered at about 166 cm(-1) and ν18-GS centered at about 818 cm(-1)) provided the GS and the excited states constants. Although the analysis of the very dense rotational patterns for such large molecules remains very challenging, relatively accurate anharmonic density functional theory calculations appeared as a highly relevant supporting tool to the analysis for both molecules. In addition, the good agreement between the experimental and calculated infrared spectrum shows that the present theoretical approach should provide useful data for the astrophysical models. Moreover, inertial defects calculated in the GS (ΔGS) of both molecules exhibit slightly negative values as previously observed for planar species of this molecular family. We adjusted the semi-empirical relations to estimate the zero-point inertial defect (Δ0) of polycyclic aromatic molecules and confirmed the contribution of low frequency out-of-plane vibrational modes to the GS inertial defects of PAHs, which is indeed a key parameter to validate the analysis of such large molecules.

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“…25 and 26 in the spectral region below 5 THz and Ref. 27 for the higher frequencies. The CO 2 lines from Ref.…”

Section: B Ftir Spectroscopy Experimentsmentioning

confidence: 85%

High resolution measurements supported by electronic structure calculations of two naphthalene derivatives: [1,5]- and [1,6]-naphthyridine—Estimation of the zero point inertial defect for planar polycyclic aromatic compounds

Gruet

Goubet

Pirali

2014

The Journal of Chemical Physics

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“…Recently, the advent of few beam lines extracting the far-IR radiation from synchrotron facilities allowed recording Fourier transform far-IR spectra exhibiting much higher SNR than with the conventional blackbody sources [23,32,42], despite a spectral resolution inherently limited to about 30 MHz for commercial instruments. The increased sensitivity of these set-ups allowed the detection of relatively weak signals as shown in our recent measurements of the far-IR water continuum absorption [43,44], or the pure rotation spectrum of O2 [45].…”

Section: Introductionmentioning

confidence: 99%

The far-infrared spectrum of 18O enriched water vapour (40–700 cm−1)

Михайленко

Béguier

Odintsova

et al. 2020

Journal of Quantitative Spectroscopy and Radiative Transfer

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The rotational spectrum of water vapour highly enriched in 18 O has been studied by high resolution (≈ 0.001 cm -1 ) Fourier transform spectroscopy at the AILES beam line of the SOLEIL synchrotron. The room temperature absorption spectrum has been recorded between 40 and 700 cm -1 . The 18 O enrichment of the sample was about 97% while the gas pressure and the absorption pathlength were set to 0.97 mbar and 151.75 m, respectively. The spectrum contains more than 4800 rotational transitions from seven water isotopologues (H2 18 O, H2 16 O, H2 17 O, HD 18 O, HD 16 O, HD 17 O, D2 18 O). The assignments were performed using known experimental energy levels as well as calculated line lists based on the results of Schwenke and Partridge. The amount and accuracy of the reported line positions represent an important extension compared to previous works. Overall, lines of about 2570 transitions are observed for the first time and 35, 41, 50, and 16 new energy levels are determined for H2 18 O, H2 17 O, HD 18 O, and HD 17 O, respectively. The set of derived energy levels shows a number of important differences from those recommended by an IUPAC-task group. Compared to the HITRAN2016 database, numerous deviations of line positions (up to 0.15 cm -1 ) are found for the H2 17 O, H2 18 O, HD 17 O, and HD 18 O species. Incomplete and wrong HITRAN's assignments of more than 90 transitions for H2 18 O, H2 17 O and HD 18 O are identified. Overall, the measured line positions will allow to significantly refine and complete the sets of empirical energy levels of H2 18 O, H2 17 O, HD 18 O and HD 17 O in the ground vibrational state.

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“…Two spectra of ethyl cyanide (99 % purity; Aldrich), with sample pressures of 26 and 500 µbar and resulting from the co-addition of 240 and 130 interferograms, were recorded to maximise the signal-to-noise ratio of the ν 13 /ν 21 and ν 20 /ν 12 bands, respectively. Residual water lines, present in the spectra, have been used for calibration purposes; their frequencies were taken from Refs [28][29][30]. The resulting spectra are presented in Fig.…”

Section: Ro-vibrational Measurementsmentioning

confidence: 99%

SOLEIL and ALMA views on prototypical organic nitriles: C2H5CN

Endres

Martin‐Drumel

Zingsheim

et al. 2021

Journal of Molecular Spectroscopy

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The high resolution vibrational spectrum of ethyl cyanide (C 2 H 5 CN) has been investigated in the far-IR using synchrotron-based Fourier transform spectroscopy. The assignment was performed using the Automated Spectral Assignment Procedure (ASAP) allowing accurate rotational energy levels of the four lowest fundamental vibrations of the species, namely the v 13 = 1 @ 205.934099(8) cm −1 , and v 21 = 1 @ 212.141101(8) cm −1 , v 20 = 1 @ 372.635293(15) cm −1 , v 12 = 1 @ 532.699617(16) cm −1 states, to be determined. The analysis not only confirms the applicability of the ASAP in the treatment of (dense) highresolution infrared spectra but also reveals some of its limitations. Complementary to the infrared study, the pure rotational spectrum of C 2 H 5 CN was also studied in selected frequency ranges from 75 to 255 GHz. New observations of a prototypical high-mass star-forming region, G327.3−0.6, performed with the Atacama Large Millimeter Array show that vibrational satellites of C 2 H 5 CN can be very intense, of order several tens of Kelvin in units of brightness temperature.

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Transferring calibration from CO2 laser lines to far infrared water lines with the aid of the ν2 band of OCS and the ν2, ν1−ν2, and ν1+ν2 bands of 13CS2: Molecular constants of 13CS2

Cited by 41 publications

References 11 publications

High resolution measurements supported by electronic structure calculations of two naphthalene derivatives: [1,5]- and [1,6]-naphthyridine—Estimation of the zero point inertial defect for planar polycyclic aromatic compounds

High resolution measurements supported by electronic structure calculations of two naphthalene derivatives: [1,5]- and [1,6]-naphthyridine—Estimation of the zero point inertial defect for planar polycyclic aromatic compounds

The far-infrared spectrum of 18O enriched water vapour (40–700 cm−1)

SOLEIL and ALMA views on prototypical organic nitriles: C2H5CN

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