Reaction Pathway and Rovibrational Analysis of Aluminum Nitride Species as Potential Dust Grain Nucleation Agents

A dust nucleating agent may be present in interstellar or circumstellar media that has gone seemingly undetected and unstudied for decades. Some analyses of the Murchison CM2 meteorite suggest that at least some of the aluminum present within condensed as aluminum nitrides instead of the long-studie...

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Bibliographic Details
Published in:The Astrophysical journal 2024-02, Vol.962 (2), p.148
Main Authors: Palmer, C. Zachary, Fortenberry, Ryan C.
Format: Article
Language:English
Subjects:
Aluminum
Aluminum hydrides
Aluminum nitride
Aluminum oxide
Ammonia
Astrochemistry
Carbon dioxide
Cosmic dust
Density functional theory
Dipole moments
Dust
Interdisciplinary astronomy
Molecular spectroscopic constants
Neutral-neutral reactions
Nucleation
Observational studies
Quantum-chemical calculations
Spectroscopic analysis
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Summary:A dust nucleating agent may be present in interstellar or circumstellar media that has gone seemingly undetected and unstudied for decades. Some analyses of the Murchison CM2 meteorite suggest that at least some of the aluminum present within condensed as aluminum nitrides instead of the long-studied, but heretofore undetected suite of aluminum oxides. The present theoretical study utilizes explicitly correlated coupled cluster theory and density functional theory to provide a formation pathway from alane (AlH 3 ) and ammonia to the cyclic structure Al 2 N 2 H 4 , which has the proper Al/N ratio expected of bulk aluminum nitrides. Novel rovibrational spectroscopic constants are computed for alane and the first two formed structures, AlNH 6 and AlNH 4 , along the reaction pathway for use as reference in possible laboratory or observational studies. The ν 8 bending frequency for AlNH 6 at 755.7 cm −1 (13.23 μ m) presents a vibrational transition intensity of 515 km mol −1 , more intense than the antisymmetric C−O stretch of carbon dioxide, and contains a dipole moment of 5.40 D, which is ∼3× larger than that of water. Thus, the present reaction pathway and rovibrational spectroscopic analysis may potentially assist in the astrophysical detection of novel, inorganic species which may be indicative of larger dust grain nucleation.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/ad182e