Vibrational, Rotational, and Electronic Spectroscopy for Possible Interstellar Detection of AlNH₂ and HAlNH

Abstract

We obtained accurate vibrational frequencies, rotational constants, and vertical transition energy for AlNH2(X1A1) and HAlNH(X1A′) isomers using ab initio calculations at various levels of theory. These two isomers are potential candidates for astronomical observation. AlNH2 and HAlNH are thermodynamically stable, with Al-NH2 and HAl-NH bond dissociation energies predicted to be 4.39 and 3.60 eV, respectively. The two isomers are characterized by sizable dipole moments of 1.211 and 3.64 D, respectively. The anharmonic frequencies and spectroscopic constants reported for the two isomers should facilitate their experimental differentiation. In addition, we evaluated the evolution of the low-lying electronic states along the stretching coordinates, as well as the absorption cross sections. AlNH2 absorbs strongly around 287, 249, and 200 nm, whereas the HAlNH absorption is centered around 370 and 233 nm.

Metallofullerenes as potential candidates for the explanation of astrophysical phenomena

“…Interestingly, metal-containing organic molecules (with metals such as Mg, Na, Al, K, Fe, and Ca) have been detected in the circumstellar environments of evolved stars, where C 60 has also been confirmed to exist. 11–13 Undeniable examples of these metal–organic molecules include MgNC, NaCN, CaNC, etc. , implying that organic species and metals can coexist in the circumstellar environment and form more complex metal–organic species.…”

Spectroscopy and Photochemistry of Aluminum-Bearing Species in the Universe

“…Using accurate theoretical methods such as standard and explicitly correlated coupled cluster theory (CCSD(T) and CCSD(T)-F12) and multireference methods such multireference configuration interaction (MRCI), it became clear that the potential along the bending angle of AlOH is flat, and the molecule may be characterized as “floppy” with a small bending mode frequency (ω 2 < 150 cm –1 ) due to the heavy aluminum atom. Interestingly, experimental , studies have determined AlOH to be a linear molecule, while the use of extensive theoretical calculations predicts a bent structure, showing the difficulty in treating this molecule computationally. ,, This uncertainty showed the need for increased investigation of other ABMs such as AlOH, , AlNX (X = S, O), AlOP, AlSO, AlCH, AlNCO, AlSiO, AlSO 2 , HAlNP, HOAlO, AlNH 2 , and AlOH 2 . It should be noted that most of the studied species are not yet experimentally accessible, and their formation mechanisms are unclear.…”