Open AccessSpectroscopic Properties Relevant to Astronomical and Laboratory Detection of MCH and MCH+ (M = Al, Mg)
Author(s) -
Vincent J. Esposito,
Tarek Trabelsi,
Joseph S. Francisco
Publication year - 2022
Publication title -
astrophysical journal/the astrophysical journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.376
H-Index - 489
eISSN - 1538-4357
pISSN - 0004-637X
DOI - 10.3847/1538-4357/ac36d0
Subject(s) - physics , excited state , atomic physics , astrochemistry , anharmonicity , dissociation (chemistry) , photoexcitation , photodissociation , radiative transfer , deuterium , interstellar medium , molecular physics , astrophysics , chemistry , optics , photochemistry , quantum mechanics , galaxy
New spectroscopic parameters have been calculated to aid in the laboratory and observational detection of AlCH, AlCH + , MgCH, MgCH + , and their deuterated analogs. All species exist in linear geometry except for AlCH + , which exhibits a bent structure. Rotational frequencies have been calculated and the transition with maximum intensity is discussed for three temperature regions present in space: 100 K for a central circumstellar envelope (CSE), 30 K for an outer CSE, and 3 K indicative of the interstellar medium. Pertinent frequencies range from 25 to 250 GHz, depending on the species. At 30 K, the most intense transition is expected to be J = 4 → 3 for all species. The vibrational spectrum of each molecule is expected to be complicated due to the flat nature of the potential energy surface along the bending angle and the presence of anharmonic resonances. Deuteration produces a decrease in vibrational frequency, which may be utilized in experiments to confirm detection of these molecules. The electronic absorption spectrum of both AlCH and MgCH is predicted to be congested and broad. Various high-oscillator-strength transitions are predicted. Upon photoexcitation in the 220–300 nm region, facile dissociation on a repulsive excited state along the Al–C coordinate is predicted to be a source of Al in the colder regions of space. Photodissociation of MgCH requires several nonradiative processes that will control the product state distribution of the fragments.