TY - JOUR

T1 - Determination of accurate rest frequencies and hyperfine structure parameters of cyanobutadiyne, HC5N

AU - Giesen, Thomas F.

AU - Harding, Michael E.

AU - Gauss, Jürgen

AU - Grabow, Jens Uwe

AU - Müller, Holger S.P.

N1 - Funding Information: We are grateful to Peter Förster for initial measurements on HC 5 N, to Holger Spahn for participation during the final experiments, and to Prof. Axel Klein and his group for preparing the HC 3 N sample used in the present investigations. We thank the Laboratoire Européen Associé de Spectroscopie Moléculaire ’LEA-HiRes’ for financial support. Additional funding was allocated by the Deutsche Forschungsgemeinschaft (DFG), in Cologne also within the Sonderforschungsbereich (SFB) 494. Further support was provided by the Länder Nordrhein-Westfalen, Niedersachen, and Hessen. The work in Mainz was supported by the DFG via grant GA 370/6-2 within the priority program SPP 1573. Our research benefited from NASA’s Astrophysics Data System (ADS).

PY - 2020/5

Y1 - 2020/5

N2 - Very accurate transition frequencies of HC5N were determined between 5.3 and 21.4 GHz with a Fourier transform microwave spectrometer. The molecules were generated by passing a mixture of HC3N and C2H2 highly diluted in neon through a discharge valve followed by supersonic expansion into the Fabry-Perot cavity of the spectrometer. The accuracies of the data permitted us to improve the experimental 14N nuclear quadrupole coupling parameter considerably and the first experimental determination of the 14N nuclear spin-rotation parameter. The transition frequencies are also well suited to determine in astronomical observations the local speed of rest velocities in molecular clouds with high fidelity. The same setup was used to study HC7N, albeit with modest improvement of the experimental 14N nuclear quadrupole coupling parameter. Quantum chemical calculations were carried out to determine 14N nuclear quadrupole and spin-rotation coupling parameters of HC5N, HC7N, and related molecules. These calculations included evaluation of vibrational and relativistic corrections to the non-relativistic equilibrium quadrupole coupling parameters; their considerations improved the agreement between calculated and experimental values substantially.

AB - Very accurate transition frequencies of HC5N were determined between 5.3 and 21.4 GHz with a Fourier transform microwave spectrometer. The molecules were generated by passing a mixture of HC3N and C2H2 highly diluted in neon through a discharge valve followed by supersonic expansion into the Fabry-Perot cavity of the spectrometer. The accuracies of the data permitted us to improve the experimental 14N nuclear quadrupole coupling parameter considerably and the first experimental determination of the 14N nuclear spin-rotation parameter. The transition frequencies are also well suited to determine in astronomical observations the local speed of rest velocities in molecular clouds with high fidelity. The same setup was used to study HC7N, albeit with modest improvement of the experimental 14N nuclear quadrupole coupling parameter. Quantum chemical calculations were carried out to determine 14N nuclear quadrupole and spin-rotation coupling parameters of HC5N, HC7N, and related molecules. These calculations included evaluation of vibrational and relativistic corrections to the non-relativistic equilibrium quadrupole coupling parameters; their considerations improved the agreement between calculated and experimental values substantially.

KW - Cyanopolyynes

KW - Hyperfine structure

KW - Interstellar molecule

KW - Microwave spectroscopy

KW - Quantum Chemical calculation

UR - http://www.scopus.com/inward/record.url?scp=85086365272&partnerID=8YFLogxK

U2 - 10.1016/j.jms.2020.111303

DO - 10.1016/j.jms.2020.111303

M3 - Article

AN - SCOPUS:85086365272

VL - 371

JO - Journal of molecular spectroscopy

JF - Journal of molecular spectroscopy

SN - 0022-2852

M1 - 111303

ER -