Millimeter Wave Spectrum of the Weakly Bound Complex CH<sub>2</sub>═CHCN·H<sub>2</sub>O: Structure, Dynamics, and Implications for Astronomical Search

Prampolini

et al. 2019

Angew Chem Int Ed

Self Cite

Rotational spectra of several difluoromethane–water adducts have been observed using two broadband chirped‐pulse Fourier‐transform microwave (CP‐FTMW) spectrometers. The experimental structures of (CH2F2)⋅⋅⋅(H2O)2, (CH2F2)2⋅⋅⋅(H2O), (CH2F2)⋅⋅⋅(H2O)3, and (CH2F2)2⋅⋅⋅(H2O)2 were unambiguously identified with the aid of 18 isotopic substituted species. A subtle competition between hydrogen, halogen, and carbon bonds is observed and a detailed analysis was performed on the complex network of non‐covalent interactions which stabilize each cluster. The study shows that the combination of stabilizing contact networks is able to reinforce the interaction strength through a cooperative effect, which can lead to large stable oligomers.

Section: Figurementioning

confidence: 99%

A General Treatment to Study Molecular Complexes Stabilized by Hydrogen‐, Halogen‐, and Carbon‐Bond Networks: Experiment and Theory of (CH₂F₂)_n⋅⋅⋅(H₂O)_m

Prampolini

et al. 2019

Angew Chem Int Ed

Self Cite

“…Argon, purchased from Società Italiana Acetilene e Derivati (SIAD), was used as the carrier gas. The rotational spectrum was recorded in the millimeter-wave region (5.03–2.72 mm and 59.6–110.0 GHz) using the Stark-modulated FJ-AMMW spectrometer previously described. − With respect to the previous setup, a HP 83712A frequency synthesizer replaced the previous HP 8671B, and with regard to the signal generation in the W band, the radiation coming from the synthesizer, once amplified by a HP 8349B, drives a HP 83558A × 6 frequency multiplier able to generate in the 75–110 GHz range. Finally, a dial attenuator was used to set the amplitude.…”

Section: Methodsmentioning

confidence: 99%

Laboratory Measurements and Astronomical Search for Thioacetamide

Maris

Favero

et al. 2019

ACS Earth Space Chem.

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Radioastronomical observations allowed for the detection of two amides (formamide and acetamide) and some sulfur-containing molecules (among them, ethanethiol and thioformaldehyde) in the interstellar medium (ISM). To understand how the chemical complexity builds up in the ISM, thioacetamide is a next-step candidate. Therefore, laboratory measurements are necessary to attempt its identification in the millimeter wavelength spectral range. The rotational spectrum of thioacetamide was recorded in the 59.6–110.0 GHz frequency region (5.03–2.72 mm) using a Stark-modulated free-jet absorption spectrometer. The spectrum is complicated by the interaction of the methyl internal rotation with the overall molecular rotation, which splits the lines into two components. Nevertheless, 300 transition lines of the parent species and 42 transition lines of the 34S isotopologue were assigned, to yield the rotational constants, the quartic centrifugal distortion constants, the 14N nuclear quarupole coupling constants, and the internal rotation parameters. We searched for thioacetamide emission toward regions associated with the star-forming process, leading to a Sun-like star. More specifically, we used the IRAM 30 m ASAI observations toward the prestellar core L1544 and the outflow shock L1157-B1. The present paper allows us to put constrains on thioacetamide abundances in low-mass star-forming regions, paving the way to future deep astronomical searches.

“…The spectrometer has a resolution of about 300 kHz and an estimated accuracy of about 50 kHz. With respect to the ordinary experimental setup described in Melandri et al (1995Melandri et al ( , 1996 and Calabrese et al (2015), some modifications on the multipliers chain were performed to obtain frequencies in the W band, more precisely, the same K-band frequency generator equipment was driving a × 4 frequency multiplier, followed by a dial attenuator. The lens limitation over 73 GHz and the over-moded driven waveguide was systematically checked and no power loss was attested up to 103 GHz.…”

Section: Methodsmentioning

confidence: 99%

Millimeter-wave spectroscopy and modeling of 1,2-butanediol

Vigorito

Melandri

et al. 2018

A&A

Context. The continuously enhanced sensitivity of radioastronomical observations allows the detection of increasingly complex organic molecules. These systems often exist in a large number of isomers leading to very congested spectra. Aims. We explore the conformational space of 1,2-butanediol and provide sets of spectroscopic parameters to facilitate searches for this molecule at millimeter wavelengths. Methods. We recorded the rotational spectrum of 1,2-butanediol in the 59.6–103.6 GHz frequency region (5.03–2.89 mm) using a free-jet millimeter-wave absorption spectrometer, and we analyzed the properties of 24 isomers with quantum chemical calculations. Selected measured transition lines were then searched on publicly available ALMA Band 3 data on IRAS 16293-2422 B. Results. We assigned the spectra of six conformers, namely aG′Ag, gG′Aa, g′G′Ag, aG′G′g, aG′Gg, and g′GAa, to yield the rotational constants and centrifugal distortion constants up to the fourth or sixth order. The most intense signal belong to the aG′Ag species, that is the global minimum. Search for the corresponding 30x,30 − 29x,29 transition lines toward IRAS 16293-2422 B was unsuccessful. Conclusions. Our present data will be helpful for identifying 1,2-butanediol at millimeter wavelengths with radio telescope arrays. Among all possible conformers, first searches should be focused on the aG′Ag conformers in the 400–800 GHz frequency spectral range.