Spectroscopy and Photochemistry of Aluminum-Bearing Species in the Universe

Abstract

Metrics & MoreArticle Recommendations CONSPECTUS: Metal-bearing molecules impact the chemical and physical environment of many astronomical sources such as the circumstellar envelopes of large asymptotic giant branch and red supergiant stars, the interstellar medium, and planetary atmospheres (e.g., ablation of ∼20 tons per day into the Earth's upper atmosphere). In recent decades, the number of successfully detected metal-containing molecules has increased via rotational spectroscopic observations, which are driven by theoretical and experimental investigations. Following formation, the ultimate fate of each species (stabilization, dissociation, etc.) is determined by its electronic structure and electronic spectroscopic properties as it encounters the pervasive radiation fields in the vacuum of space. Studying these properties can evince the possibility of detection and predict the impact each molecule has on its surrounding environment. Aluminum, one of the most abundant elements and metals, is distributed throughout the universe as a constituent of gas-phase molecules (e.g., AlO, AlOH, AlCl, etc.) as well as condensed onto solid dust grains such as Al 2 O 3 . Free gas-phase aluminum-bearing molecules are synthesized by nonthermal equilibrium processes such as shocks and pulsations near the stellar photosphere or via the reaction of molecules on the surface of dust grains. Recent investigations in our research group utilizing quantum chemical methods, such as coupled cluster (CCSD(T) and CCSD(T)-F12) and multireference configuration interaction (MRCI) with large basis sets, have explored a wide breadth of spectroscopy and photochemistry of small (triatomic and tetratomic) aluminum-bearing molecules,

Spectroscopy and Photochemistry of [Al, N, C, O, H]: Connectivity to Aluminium‐Bearing Species in the Universe

“…For instance, VY CMa has a plethora of NC‐bearing species (e. g., HNC, HCN, CH 3 CN, and CN) along with the reactive AlO and AlOH, [7b] which sets the stage for the possible existence of AlCN and even more complex organometallic compounds [Al, N, C, H], [Al, N, C, O] as well as [Al, N, C, O, H] (Figure 1). [1a,13] The identification of new molecules in CSEs and ISM typically relies on preliminary spectroscopic characterizations in the laboratory [13a] . Recent investigations employing quantum chemistry methods have delved into the spectra and thermochemistry of a wide breadth of small Al‐bearing molecules, especially those including Al−H, Al−C, Al−N, and Al−O bonds [13,14] .…”