"First Interstellar Detection Of Isocyanodiacetylene (<span Class=""roman"">hc</span>_{<span Class=""roman"">4</span>}<span Class=""roman"">nc</span>), The Largest Isocyanide Molecule In The Ism"

Xue, Ci

Permalink

https://hdl.handle.net/2142/111146 Copy

Description

Title

"First Interstellar Detection Of Isocyanodiacetylene (hc₄nc), The Largest Isocyanide Molecule In The Ism"

Author(s)

Xue, Ci

Contributor(s)

• McGuire, Brett A.
• Lee, Kelvin
• Burkhardt, Andrew M.
• Loomis, Ryan A
• Remijan, Anthony
• Herbst, Eric
• Willis, Eric R.

Issue Date

2021-06-22

Keyword(s)

Astronomy

Abstract

The cyanide and isocyanide (-\chem{CN} and -\chem{NC}) pairs of isomers have been used regularly to probe the physical conditions and history of interstellar sources and to improve the accuracy and predictive power of astrochemical models. Two examples are the strong sensitivity of the $\chem{HCN}$/$\chem{HNC}$ abundance ratio to the gas kinetic temperatures\footnote{A. Hacar, A. D. Bosman, and E. F. van Dishoeck, A\&A 635, A4(2020)} and the dependence of the $\chem{CH_3CN}$/$\chem{CH_3NC}$ abundance ratio to the cosmic-ray ionization rates\footnote{E. R. Willis, et al., A\&A, 636, A29 (2020)}. Yet, despite the numerous detections of cyanides in astronomical environments, there have been very few confirmed detections of isocyanides. Alongside $\chem{C_nH_{2n+1}CN}$, one of the most frequently observed families of cyanide species in cold sources are the cyanopolyynes ($\chem{HC_{2n}CN}$). In contrast to their ubiquity, the only isocyanide version that had been successfully detected is $\chem{HCCNC}$, the isomer of $\chem{HC_3N}$. In this talk, we will present the first astronomical detection of the largest isocyanide molecule, isocyanodiacetylene ($\chem{HC_4NC}$), using the data available from the GOTHAM (Green Bank Telescope Observations of TMC-1: Hunting for Aromatic Molecules) observational program of TMC-1\footnote{B. A. McGuire, et al., ApjL, 900, L10 (2020)}. Assisted by a cutting-edge application of spectral line stacking and matched filtering techniques, we determined the \chem{NC}/\chem{CN} isomeric intensity ratios of the $\chem{HC_{2n}NC}$/$\chem{HC_{2n}CN}$ family rigorously for n=1 and 2 toward TMC-1 and provided an upper limit of that for n=3. The abundance ratios derived from observations helped in constraining the interplay between -\chem{CN} and -\chem{NC} formation chemistry and their dependence on the physico-chemical history of the source. This work also demonstrated the need for a detailed investigation of the related formation pathways in the laboratory.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

Text

Language

eng

Permalink

http://hdl.handle.net/2142/111146

DOI

10.15278/isms.2021.TJ03

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