Computing Accurate & Reliable Rovibrational Spectral Data for Aluminum-Bearing Molecules.

The difficulty of quantum chemically computing vibrational, rotational, and rovibrational reference data via quartic force fields (QFFs) for molecules containing aluminum appears to be alleviated herein using a hybrid approach based upon CCSD(T)-F12b/cc-pCVTZ further corrected for conventional CCSD(T) scalar relativity within the harmonic terms and simple CCSD(T)-F12b/cc-pVTZ for the cubic and quartic terms: the F12-TcCR+TZ QFF. Aluminum containing molecules are theorized to participate in significant chemical processes in both the Earth's upper atmosphere as well as within circumstellar and interstellar media. However, experimental data for the identification of these molecules are limited, showcasing the potential for quantum chemistry to contribute significant amounts of spectral reference data.

Rovibrational analysis of AlCO3, OAlO2, and HOAlO2 for possible atmospheric detection.

The lack of observational data for the AlO molecule in the mesosphere/lower thermosphere may be due to ablated aluminum reacting quickly to form other species. Previously proposed reaction pathways show that aluminum could be ablated in the atmosphere from meteoritic activity, but there currently exist very limited spectroscopic data on the intermediates in these reactions, limiting the possible detection of said molecules. As such, rovibrational spectroscopic data are computed herein using quartic force field methodology at four different levels of theory for the neutral intermediates AlCO3, OAlO2, and HOAlO2.

From Benzonitrile to Dicyanobenzenes: The Effect of an Additional CN Group on the Thermochemistry and Negative Ion Photoelectron Spectra of Dicyanobenzene Radical Anions.

The negative ion photoelectron spectra of 1,2-dicyanobenzene (-DCNB), 1,3-dicyanobenzene (-DCNB), and 1,4-dicyanobenzene (-DCNB) radical anions (DCNB·), acquired through the computation of Frack-Condon (FC) factors, are presented. The FC calculations utilize harmonic frequencies and normal mode vectors derived from density functional theory at the B3LYP/aug-cc-pVQZ basis set. All the totally symmetric vibrational modes are treated with Duschinsky rotations to yield neutral DCNBs in their singlet (S) and lowest triplet (T) states, following an electron removal from the doublet anionic ground state.

Negative Ion Photoelectron Spectra of Deprotonated Benzonitrile Isomers via Computation of Franck-Condon Factors.

Negative ion photoelectron spectra of (-), (-), and (-) deprotonated benzonitrile (-, -, -CH(CN)) isomers as well as the associated thermochemical values corresponding to deprotonation at -, -, and -positions in CH(CN) are presented. Quantum mechanical results based on the density functional theory (DFT) utilizing the aug-cc-pVQZ basis set indicate that the -, -, -CH(CN) radicals have electron affinity values (EAs) of 1.901, 1.