Determination of accurate rest frequencies and hyperfine structure parameters of cyanobutadiyne, HC${}_5$N

Abstract

Very accurate transition frequencies of HC${}_5$N were determined between 5.3 and 21.4 GHz with a Fourier transform microwave spectrometer. The molecules were generated by passing a mixture of HC${}_3$N and C${}_2$H${}_2$ 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 ${}^{14}$N nuclear quadrupole coupling parameter considerably and the first experimental determination of the ${}^{14}$N 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 HC${}_7$N, albeit with modest improvement of the experimental ${}^{14}$N nuclear quadrupole coupling parameter. Quantum chemical calculations were carried out to determine ${}^{14}$N nuclear quadrupole and spin-rotation coupling parameters of HC${}_5$N, HC${}_7$N, 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.

arXiv comment9 pages; J. Mol. Spectrosc., accepted

References in corpus (12)

• The Cologne Database for Molecular Spectroscopy, CDMS, in the Virtual Atomic and Molecular Data Centre, VAMDC
• Accurate rest frequencies of methanol maser and dark cloud lines
• Rotational spectra of isotopic species of methyl cyanide, CH${}_3$CN, in their ground vibrational states up to terahertz frequencies
• Rotational spectroscopy as a tool to investigate interactions between vibrational polyads in symmetric top molecules: low-lying states $v_8\le 2$ of methyl cyanide, CH${}_3$CN
• Non-Detection of HC${}_{11}$N toward TMC-1: Constraining the Chemistry of Large Carbon-Chain Molecules
• Rotational spectroscopy, dipole moment and ${}^{14}$N nuclear hyperfine structure of $iso$-propyl cyanide
• Physical conditions in the Protoplanetary Nebula CRL 618 derived from observations of vibrationally excited HCCCN
• Detection of HC${}_5$N and HC${}_7$N Isotopologues in TMC-1 with the Green Bank Telescope
• Laboratory spectroscopic study of isotopic thioformaldehyde, H${}_2$CS, and determination of its equilibrium structure
• Rotational and high-resolution infrared spectrum of HC${}_3$N: global ro-vibrational analysis and improved line catalogue for astrophysical observations
• ${}^{13}$C isotopic fractionation of HC${}_3$N in two starless cores: L1521B and L134N (L183)
• First Detection of HC${}_5$${}^{15}$N in the Interstellar Medium

Cited by in corpus (4)

• Tentative detection of HC5NH+ in TMC-1
• The magnesium paradigm in IRC+10216: Discovery of MgC${}_4$H${}^{+}$, MgC${}_3$N${}^{+}$, MgC${}_6$H${}^{+}$, and MgC${}_5$N${}^{+}$
• Cyanopolyyne chemistry in the L1544 prestellar core: new insights from GBT observations
• Reexploring Molecular Complexity with ALMA: Insights into chemical differentiation from the molecular composition of hot cores in Sgr B2(N2)