The pure rotational spectrum of the T-shaped AlC2 radical (: X 2A1)

D. T. Halfen, Lucy M Ziurys

Research output: Contribution to journalArticle

Abstract

The pure rotational spectrum of the AlC2 radical (X2A1) has been measured using Fourier transform microwave/millimeter-wave (FTMmmW) techniques in the frequency range 21-65 GHz. This study is the first high-resolution spectroscopic investigation of this molecule. AlC2 was created in a supersonic jet from the reaction of aluminum, generated by laser ablation, with a mixture of CH4 or HCCH, diluted in argon, in the presence of a DC discharge. Three transitions (NKa,Kc = 101 → 000, 202 → 101, and 303 → 202) were measured, each consisting of multiple fine/hyperfine components, resulting from the unpaired electron in the species and the aluminum-27 nuclear spin (I = 5/2). The data were analyzed using an asymmetric top Hamiltonian and rotational, fine structure, and hyperfine constants determined. These parameters agree well with those derived from previous theoretical calculations and optical spectra. An r0 structure of AlC2 was determined with r(Al-C) = 1.924 Å, r(C-C) = 1.260 Å, and (C-Al-C) = 38.2°. The Al-C bond was found to be significantly shorter than in other small, Al-bearing species. The Fermi contact term established in this work indicates that the unpaired electron in the valence orbital has considerable 3pza1 character, suggesting polarization towards the C2 moiety. A high degree of ionic character in the molecule is also evident from the quadrupole coupling constant. These results are consistent with a T-shaped geometry and an Al+C2 - bonding scheme. AlC2 is a possible interstellar molecule that may be present in the circumstellar envelopes of carbon-rich AGB stars.

Original languageEnglish (US)
Pages (from-to)11047-11052
Number of pages6
JournalPhysical Chemistry Chemical Physics
Volume20
Issue number16
DOIs
StatePublished - Jan 1 2018

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rotational spectra
Aluminum
Molecules
aluminum 27
Bearings (structural)
molecules
Hamiltonians
carbon stars
Electrons
Argon
asymptotic giant branch stars
Laser ablation
Millimeter waves
nuclear spin
millimeter waves
laser ablation
Stars
optical spectrum
electric contacts
Fourier transforms

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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The pure rotational spectrum of the T-shaped AlC2 radical ( : X 2A1). / Halfen, D. T.; Ziurys, Lucy M.

In: Physical Chemistry Chemical Physics, Vol. 20, No. 16, 01.01.2018, p. 11047-11052.

Research output: Contribution to journalArticle

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