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Water is a fundamental molecule for life, and investigating its interaction with monosaccharides is of great interest in order to understand its influence on their conformational behavior. In this study, we report on the conformational landscape of monosaccharide glyceraldehyde, the simplest aldose sugar, in the presence of a single water molecule in the gas phase. This investigation was performed using a combination of Fourier transform microwave spectroscopy and theoretical calculations. Out of the nine calculated conformers, only the lowest energy conformer was experimentally observed and characterized. Interestingly, the presence of water was found to induce structural features in the lowest energy conformer of the glyceraldehyde monomer, with water positioned between the alcohol groups. To analyze this interaction further, non-covalent interaction plots were employed to map the intermolecular interactions in the observed species. Additionally, natural bond orbital analysis was conducted to study the effects of charge transfer in the monohydrate system. Furthermore, topological analysis based on Bader's Atoms in Molecules theory was performed to gain insights into the observed complex. The results of all three analyses consistently showed the formation of relatively strong hydrogen bonds between water and glyceraldehyde, leading to the formation of a seven-member ring network. [ABSTRACT FROM AUTHOR]

The gas-phase rotational spectra of α-pinene oxide have been recorded using a chirped-pulse Fourier transform microwave spectrometer in the 6–18 GHz frequency range. The parent species and all heavy atom isotopologues (13C and 18O) have been observed in their natural abundance. The experimental rotational constants of all isotopic species observed have been determined and used to obtain the substitution (rs) and the effective (r0) structures of the most stable conformer of α-pinene oxide. Calculations using the density functional theories B3LYP, M06-2X, and MN15-L and the ab initio method MP2 level of theory were carried out to check their performance against experimental results. The structure of the heavy atom's skeleton of α-pinene oxide has been compared to that of α-pinene and has shown that epoxidation does not overly affect the structure of the bicycle, validating its robustness. Furthermore, the structural features have been compared to those of other bicyclic molecules, such as nopinone and β-pinene. [ABSTRACT FROM AUTHOR]

A color center laser spectrometer along with velocity modulation detection was used to record the absorption spectrum of H2O+ produced in an AC glow discharge between 3180 and 3390 cm-1 with a gas mixture of He/H2O. The predominant role of the reaction of metastable helium with H2O has been observed. The H2O+ ion is also present in the spectra recorded between 3100 and 3600 cm-1 with a gas mixture of He/H2/O2 and some features are illustrated. The ν1 and ν2+ν3-ν2 bands have been assigned and the previous analysis of the ν3 band [J. Mol. Spectrosc. 127, 1 (1988)] has been extended. The ν1 and ν3 states have been fitted together taking into account the vibration–rotation interaction. The molecular constants have been obtained for the ν1 and ν2+ν3 states and they have been improved in the case of the ν3 and the ground vibrational states. The equilibrium structure has been derived [re=0.9992(6) Å, θe=109.30(10)°] and the quadratic and cubic force field constants have been evaluated. [ABSTRACT FROM AUTHOR]

Improved sets of data have been recorded and analyzed in order to study the bending rovibrational energy levels of C2D2, in the regions of the ν5–ν4 difference band (FIR) and of the ν5 fundamental band (IR). A matrix model is setup to deal with a Darling–Dennison coupling between sets of bending levels as well as with the usual l-type resonances. A simultaneous fit of the new data together with earlier microwave measurements produces an extended set of very accurate parameters, including for the first time in C2D2 s45 and qkt. [ABSTRACT FROM AUTHOR]

The conformational landscape of myrtenol (2-pinen-10-ol) and its robustness upon hydration were investigated theoretically and experimentally by employing a synergic combination of quantum chemical calculations and Fourier transform microwave spectroscopy coupled to a supersonic jet expansion. Relaxed potential energy surfaces have been carried out, and the lowest energy conformers of the monomer were found to be associated with different geometries of the hydroxymethyl group from those previously reported [Sedo et al., J. Mol. Spectrosc. 356, 32 (2019)]. Geometry optimizations and harmonic vibrational frequency calculations allowed characterization of the equilibrium structure of the possible conformers of myrtenol. Among the nine predicted structures, four have been observed, analyzed, and identified. The controversy on the geometry was solved with the deuteration of the hydroxyl group, which led to the determination of substitution (rs) geometry, in agreement with the present theoretical results. Interestingly, the four observed conformers exhibit the same orientation of OH as in the allyl alcohol molecule. Furthermore, hydrogen bonding linking myrtenol to water was studied. One monohydrate has been observed and identified. Non-covalent interactions and natural bond orbital analysis were performed to depict the interactions responsible for the stabilization of the observed structure. We conclude that the structure of the hydroxymethyl group is robust and does not change upon hydration. [ABSTRACT FROM AUTHOR]

Laboratory analysis of spectra of potential interstellar molecules from the radio-frequency to the THz range is a prerequisite for their subsequent identification by radioastronomical techniques. The spectral analysis allows us to derive molecular parameters that are able to model the frequency and intensity patterns of the transitions, as well as to predict with a high degree of precision the frequencies of transitions not measured in the laboratory. [ABSTRACT FROM AUTHOR]

The magnetic hyperfine structure of the non-rigid methanol molecule is investigated experimentally and theoretically. 12 hyperfine patterns are recorded using molecular beam microwave spectrometers. These patterns, along with previously recorded ones, are analyzed in an attempt to evidence the effects of the magnetic spin-torsion coupling due to the large amplitude internal rotation of the methyl group [J. E. M. Heuvel and A. Dymanus, J. Mol. Spectrosc. 47, 363 (1973)]. The theoretical approach setup to analyze the observed data accounts for this spin-torsion in addition to the familiar magnetic spin-rotation and spin-spin interactions. The theoretical approach relies on symmetry considerations to build a hyperfine coupling Hamiltonian and spin-rotation-torsion wavefunctions compatible with the Pauli exclusion principle. Although all experimental hyperfine patterns are not fully resolved, the line position analysis yields values for several parameters including one describing the spin-torsion coupling. [ABSTRACT FROM AUTHOR]

The hyperfine structure of methyl formate was recorded in the 2-20 GHz range. A molecular beam coupled to a Fourier transform microwave spectrometer having an instrumental resolution of 0.46 kHz and limited by a Doppler width of a few kHz was used. A-type lines were found split by the magnetic hyperfine coupling while no splittings were observed for E-type lines. Symmetry considerations were used to account for the internal rotation of the methyl top and to derive effective hyperfine coupling Hamiltonians. Neglecting the spin-rotation magnetic coupling, the vanishing splittings of the E-type lines could be understood and analyses of the hyperfine patterns of the A-type lines were performed. The results are consistent with a hyperfine structure dominated by the magnetic spin-spin coupling due to the three hydrogen atoms of the methyl group. [ABSTRACT FROM AUTHOR]

Organic isocyanides have an interesting astrochemistry and some of these molecules have been detected in the interstellar medium (ISM). However, rotational spectral data for this class of compounds are still scarce. We provide laboratory spectra of the four-carbon allyl isocyanide covering the full microwave region, thus allowing a potential astrophysical identification in the ISM. We assigned the rotational spectrum of the two cis (synperiplanar) and gauche (anticlinal) conformations of allyl isocyanide in the centimeter-wave region (4-18 GHz), resolved its 14N nuclear quadrupole coupling (NQC) hyperfine structure, and extended the measurements into the millimeter and submillimeter-wave (150-900 GHz) ranges for the title compound. Rotational constants for all the monosubstituted 13C and 15N isotopologues are additionally provided. Laboratory observations are supplemented with initial radioastronomical observations. Following analysis of an extensive dataset (>11000 rotational transitions), accurate ground-state molecular parameters are reported for the cis and gauche conformations of the molecule, including rotational constants, NQC parameters, and centrifugal distortion terms up to octic contributions. Molecular parameters have also been obtained for the two first excited states of the cis conformation, with a dataset of more than 3300 lines. The isotopic data allowed determining substitution and effective structures for the title compound. We did not detect allyl isocyanide either in the IRAM 30 m line survey of Orion KL or in the PRIMOS survey toward SgrB2. Nevertheless, we provided an upper limit to its column density in Orion KL. [ABSTRACT FROM AUTHOR]

Context. Astronomical surveys of interstellar molecules, such as those that will be available with the very sensitive ALMA telescope, require preliminary laboratory investigations of the microwave and submillimeter-wave spectra of new molecular species to identify these in the interstellar media. Aims. We build a linelist that should allow us to detect HCOOCD2H, provided it is present in the interstellar media in a suitable concentration. Methods. The experimental spectra of HCOOCD2H have been recorded in the microwave and submillimeter-wave energy range. Line frequencies were analyzed using an internal axis method-like treatment taking into account the CD2H internal rotation. Results. 5933 lines of HCOOCD2H have been assigned and their frequencies were reproduced with a unitless standard deviation"" of 1.6. A linelist with calculated frequencies and intensities was built and spans the 50-660 GHz spectral region. The frequency accuracy is better than 0.1 MHz. Conclusions. The pure rotation spectrum of the CD2H-methyl formate isotopolog (HCOOCD2H) has been observed in laboratory for the first time [ABSTRACT FROM AUTHOR]

The rotational spectrum of chlorofluoroiodomethane (CHClFI) has been investigated. Because its rotational spectrum is extremely crowded, extensive ab initio calculations were first performed in order to predict the molecular parameters. The low J transitions were measured using a pulsed-molecular-beam Fourier transform spectrometer, and the millimeter-wave spectrum was measured to determine accurate centrifugal distortion constants. Because of the high resolution of the experimental techniques, the analysis yielded accurate rotational constants, centrifugal distortion corrections, and the complete quadrupole coupling tensors for the iodine and chlorine nuclei, as well as the contribution of iodine to the spin−rotation interaction. These molecular parameters were determined for the two isotopologs CH35ClFI and CH37ClFI. They reproduce the observed transitions within the experimental accuracy. Moreover, the ab initio calculations have provided a precise equilibrium molecular structure. Furthermore, the ab initio molecular parameters are found in good agreement with the corresponding experimental values. [ABSTRACT FROM AUTHOR]

Line intensities and self-broadening coefficients in the ν 1 + 3ν 3 band of 12 C 2 H 2 near 0.8 µm at room temperature were measured by means of both laser photoacoustic and Fourier transform spectroscopy. An experimental protocol has been developed to obtain absolute intensities from the photoacoustic measurements. Namely, the spectrometer was calibrated using water vapour line intensities available in Hitran 1996 [L. S. Rothman et al . (1998) J. quant. Spectrosc. Radiat. Transfer , 60, 665-710]. These photoacoustic line intensities were found to be on average 5% higher than corresponding measurements performed using Fourier transform spectroscopy, the accuracy of the latter being estimated to better than 4%. The accuracy of the photoacoustic intensities is discussed. Previous results from the literature [F. Herregodts, D. Hurtmans, J. Vander Auwera, and M. Herman (1999) J. chem. Phys. , 111, 7954-7960] are revised. [ABSTRACT FROM AUTHOR]

This work continues a series of papers devoted to the analysis of the vibration–rotation energy structure of OCS with a global effective model. A spectrum of natural carbonyl sulfide in the near infrared region was recorded at room temperature with a gas pressure of 120 hPa. A laser photoacoustic spectrometer consisting of a longitudinal resonant cell coupled to a titanium : sapphire ring laser was employed. Twelve new overtone and combination bands were observed at high resolution in the region between 10 890 and 14 000 cm−: 1005–0000, 1404–0000, 0205–0000, 2404–0000, 2005–0000, 131e5–011e0, 131f5–011f0, 1205–0000, 2205–0000, 3005–0000, 1116–0110, and 0007–0000. Effective state parameters were obtained from the band-by-band least-squares fits. The new data introduced in the global analysis with the molecular parameters obtained by E. Rbaihi, A. Belafhal, J. Vander Auwera, S. Naı¨m, and A. Fayt (J. Mol. Spectrosc.191, 32–44, 1998) are reproduced within or very near the experimental accuracy. Relative line intensities have been considered to study the coupling between the states. Perturbations and intensity transfers are fully understood with the present model. [Copyright &y& Elsevier]

Methacrolein is a major oxidation product of isoprene emitted in the troposphere. New spectroscopy information is provided with the aim to allow unambiguous identification of this complex molecule, characterized by a large amplitude motion associated with the methyl top. State-of-the-art millimeter-wave spectroscopy experiments coupled to quantum chemical calculations have been performed. For the most stable s-trans conformer of atmospheric interest, the torsional and rotational structures have been characterized for the ground state, the first excited methyl torsional state (ν27), and the first excited skeletal torsional state (ν26). The inverse sequence of A and E tunneling sub-states as well as anomalous A-E splittings observed for the rotational lines of v26 = 1 state clearly indicates a coupling between methyl torsion and skeletal torsion. A comprehensive set of molecular parameters has been obtained. The far infrared spectrum of Durig et al. [Spectrochim. Acta, Part A 42, 89-103 (1986)] was reproduced, and a Fermi interaction between ν25 and 2ν27 was evidenced. [ABSTRACT FROM AUTHOR]

The far infrared spectrum of cis-methyl formate has been recorded on the AILES beamline of the synchrotron SOLEIL using a Fourier transform infrared spectrometer coupled to a long path cell. The very weak fundamental band associated with the methyl-top torsion mode (ν18) was observed. The frequency analysis was performed using the 'rho axis method', and the microwave and millimeter-wave data from the literature. A precise determination of the band origins (ν18A = 132.4303 cm-1 and ν18E = 131.8445 cm-1) and of the barrier height [V3 = 370.7398 (58) cm-1] have been obtained. The intensity of the ν18 fundamental band was determined to be 3.4 × 10-21 cm-1/(molecule cm-2) at 297 K, equally shared among A-A and E-E transitions, thus leading to a dipole moment component μc(3) equal to 0.0483 D. The results were compared with the ab initio calcula-tions of Senent et al. [Astrophys. J. 627, 567 (2005)]. [ABSTRACT FROM AUTHOR]

The rotational structure of the local mode Si-H stretching vibrational bands (n00 A[sub 1]/E), n=3, 4, and 6, of H[sub 3][SUP ARRANGE="STAGGER"]28]SiD have been studied by high-resolution Fourier transform infrared and by photoacoustic laser spectroscopy. The recorded bands have been rotationally analyzed with a Hamiltonian model which makes use of simple arithmetic relations between some of the rovibrational parameters. While the (300 A[sub 1]/E) states were found to be unperturbed, severe perturbations by unknown dark states affect the (400 A[sub 1]/E) and (600 A[sub 1]/E) states for J values exceeding 8. Ab initio calculations have been performed to form the quadratic and the cubic potential energy surfaces which have been used to calculate spectroscopic parameters for the Si-H stretching fundamentals. These results, together with the local mode relations, have been successfully used to model the vibrational dependence of effective rovibrational parameters in the excited local mode states. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Sulphur hexafluoride is a very strong greenhouse gas whose concentration is increasing in the atmosphere. It is detected through infrared absorption spectroscopy in the strong ν3fundamental region. Due to the existence of low-lying vibrational states of this molecule, however, many hot bands arise at room temperature and those are still not known. We present here a contribution to the elucidation of this hot band structure, by analysing the ν2+ ν3combination band. We use a supersonic jet expansion high-resolution spectrum at a rotational temperature of ca. 25 K that was recorded thanks to the Jet-AILES setup at the Source Optimisée de Lumière d’Energie Intermédiaire du LURE (SOLEIL) Synchrotron. The simplified structure of this cold spectrum allowed us to assign 444 rovibrational lines and to fit effective Hamiltonian parameters, leading to a very satisfactory spectrum simulation. The parameters obtained in this way allow to calculate the spectrum of the ν3+ν2−ν2hot band. [ABSTRACT FROM AUTHOR]

Context. Glycolaldehyde (CH2OHCHO) is the simplest sugar and an important intermediate in the path toward forming more complex biologically relevant molecules. Astronomical surveys of interstellar molecules, such as those available with the very sensitive ALMA telescope, require preliminary laboratory investigations of the microwave and submillimeter-wave spectra of molecular species including new isotopologs - to identify these in the interstellar media. Aims. To achieve the detection of the 13C isotopologs of glycolaldehyde in the interstellar medium, their rotational spectra in the millimeter and submillimeter-wave regions were studied. Methods. The spectra of 13CH2OHCHO and CH2OH13CHO were recorded in the 150-945 GHz spectral range in the laboratory using a solid-state submillimeter-wave spectrometer in Lille. The observed line frequencies were measured with an accuracy of 30 kHz up to 700 GHz and of 50 kHz above 700 GHz. We analyzed the spectra with a standard Watson Hamiltonian. Results. About 10 000 new lines were identified for each isotopolog. The spectroscopic parameters were determined for the groundand the three lowest vibrational states up to 945 and 630 GHz. Previous microwave assignments of 13CH2OHCHO were not confirmed. Conclusions. The provided line-lists and sets of molecular parameters meet the needs for a first astrophysical search of 13C-glycolaldehydes. [ABSTRACT FROM AUTHOR]

Context. Astronomical survey of interstellar molecular clouds needs a previous analysis of the spectra in the microwave and sub-mm energy range to be able to identify them. We obtained very accurate spectroscopic constants in a comprehensive laboratory analysis of rotational spectra. These constants can be used to predict transition frequencies that were not measured in the laboratory very precisely. Aims. We present an experimental study and a theoretical analysis of two 18O-methyl formate isotopologues, which were subsequently detected for the first time in Orion KL. Methods. The experimental spectra of both methyl formate isotopologues recorded in the microwave and sub-mm range from 1 to 660 GHz. Both spectra were analysed by using the rho-axis method (RAM) which takes into account the CH3 internal rotation. Results. We obtained spectroscopic constants of both 18O- methyl formate with high accuracy. Thousands of transitions were assigned and others predicted, which allowed us to detect both species in the IRAM 30 m line survey of Orion KL. [ABSTRACT FROM AUTHOR]