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Title: Laboratory and Astronomical Discovery of Magnesium Dicarbide, MgC 2
Abstract We report the detection of magnesium dicarbide, MgC 2 , in the laboratory at centimeter wavelengths and assign 24 MgC 2 , 25 MgC 2 , and 26 MgC 2 to 14 unidentified lines in the radio spectrum of the circumstellar envelope of the evolved carbon star IRC+10216. The structure of MgC 2 is found to be T-shaped with a highly ionic bond between the metal atom and the C 2 unit, analogous to other dicarbides containing electropositive elements. A two-temperature excitation model of the MgC 2 emission lines observed in IRC+10216 yields a very low rotational temperature of 6 ± 1 K, a kinetic temperature of 22 ± 13 K, and a column density of (1.0 ± 0.3) × 10 12 cm −2 . The abundance of MgC 2 relative to the magnesium–carbon chains MgCCH, MgC 4 H, and MgC 6 H is 1:2:22:20 and provides a new constraint on the sequential radiative association–dissociative recombination mechanisms implicated in the production of metal-bearing molecules in circumstellar environments.  more » « less
Award ID(s):
2110489
PAR ID:
10407639
Author(s) / Creator(s):
; ; ; ; ; ; ; ;
Date Published:
Journal Name:
The Astrophysical Journal Letters
Volume:
940
Issue:
2
ISSN:
2041-8205
Page Range / eLocation ID:
L42
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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