Reaction Pathway and Rovibrational Analysis of Aluminum Nitride Species as Potential Dust Grain Nucleation Agents. (arXiv:2401.06288v1 [astro-ph.IM])
<a href="http://arxiv.org/find/astro-ph/1/au:+Palmer_C/0/1/0/all/0/1">C. Zachary Palmer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fortenberry_R/0/1/0/all/0/1">Ryan C. Fortenberry</a>
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 pathway of formation 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 $nu_8$ bending frequency for AlNH$_6$ at 755.7
cm$^{-1}$ (13.23 $mu$m) presents a vibrational transition intensity of 515 km
mol$^{-1}$, slightly more intense than the anti-symmetric C$-$O stretch of
carbon dioxide, and contains a dipole moment of 5.40 D, which is $sim 3
times$ 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.
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 pathway of formation 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 $nu_8$ bending frequency for AlNH$_6$ at 755.7
cm$^{-1}$ (13.23 $mu$m) presents a vibrational transition intensity of 515 km
mol$^{-1}$, slightly more intense than the anti-symmetric C$-$O stretch of
carbon dioxide, and contains a dipole moment of 5.40 D, which is $sim 3
times$ 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.
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