Ab Initio Study of Fine and Hyperfine Interactions in Triplet POH

Abstract

Phosphorous-containing molecules have a great relevance in prebiotic chemistry in view of the fact that phosphorous is a fundamental constituent of biomolecules, such as RNA, DNA, and ATP. Its biogenic importance has led astrochemists to investigate the possibility that P-bearing species could have formed in the interstellar medium (ISM) and subsequently been delivered to early Earth by rocky bodies. However, only two P-bearing molecules have been detected so far in the ISM, with the chemistry of interstellar phosphorous remaining poorly understood. Here, in order to shed further light on P-carriers in space, we report a theoretical spectroscopic characterisation of the rotational spectrum of POH in its 3A″ ground electronic state. State-of-the-art coupled-cluster schemes have been employed to derive rotational constants, centrifugal distortion terms, and most of the fine and hyperfine interaction parameters, while the electron spin–spin dipolar coupling has been investigated using the multi-configuration self-consistent-field method. The computed spectroscopic parameters have been used to simulate the appearance of triplet POH rotational and ro-vibrational spectra in different conditions, from cold to warm environments, either in gas-phase experiments or in molecular clouds. Finally, we point out that the predicted hyperfine structures represent a key pattern for the recognition of POH in laboratory and interstellar spectra.

From the laboratory to the interstellar medium: a strategy to search for exotic molecules in space

“…In the case of openshell species, the situation is more involved because the coupling of the rotational angular momentum with the electronic spin momentum should be incorporated in the treatment (Gordy and Cook, 1984;Cazzoli et al, 2016). If more than one unpaired electrons are present, the coupling between the electronic spins should also been considered (Gordy and Cook, 1984;Cazzoli et al, 2016;Bizzocchi et al, 2022).…”

“…If more than one electron is present, then H fs also incorporates the electron spin-spin interaction (through the electron spin-spin coupling tensor λ which is symmetric and traceless). If nonzero nuclear spins are present in the molecule, in addition to the hyperfine interactions mentioned above, a hyperfine-structure term describing the interaction between the electron spin and the nuclear spins should be incorporated in the Hamiltonian above (Gordy and Cook, 1984;Bizzocchi et al, 2022).…”