Ab Initio Study of Fine and Hyperfine Interactions in Triplet POH

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.

Precisely spun super rotors

Improved optical control of molecular quantum states promises new applications including chemistry in the quantum regime, precision tests of fundamental physics, and quantum information processing. While much work has sought to prepare ground state molecules, excited states are also of interest. Here, we demonstrate a broadband optical approach to pump trapped SiO+ molecules into pure super rotor ensembles maintained for many minutes. Super rotor ensembles pumped up to rotational state N = 67, corresponding to the peak of a 9400 K distribution, had a narrow N spread comparable to that of a few-kelvin sample, and were used for spectroscopy of the previously unobserved C2Π state. Significant centrifugal distortion of super rotors pumped up to N = 230 allowed probing electronic structure of SiO+ stretched far from its equilibrium bond length.

Спектр высокого разрешения полос ν-=SUB=-2-=/SUB=-+ν-=SUB=-4-=/SUB=- (F-=SUB=-1-=/SUB=-,F-=SUB=-2-=/SUB=-) и 2ν-=SUB=-4-=/SUB=- (F-=SUB=-2-=/SUB=-) дейтерированного силана -=SUP=-28-=/SUP=-SiD-=SUB=-4-=/SUB=-

A study of the fine rotational structure of the silane molecule absorption spectrum was carried out for the first time. The high-resolution spectrum of 28SiD4 was recorded in the 1260-1480 cm-1 spectral range the vibrational ν2+ν4 (F1,F2) and 2ν4 (F2) bands were theoretically analyzed. Rotational, centrifugal distortion, tetrahedral splitting and resonance interaction parameters of the upper vibrational states were obtained from the weighted least square fit method. The set parameters obtained reproduces the initial vibrational-rotational structure of the ν2 + ν4 (F1, F2) and 2ν4 (F2) bands with an accuracy of drms = 3.9 · 10-4 cm-1.

The smell of coffee: the carbon atom microwave structure of coffee furanone validated by quantum chemistry

The rotational spectra of coffee furanone (2-methyltetrahydrofuran-3-one) have been measured in the frequency range from 2.0 to 26.5 GHz using a molecular jet Fourier transform microwave spectrometer. Quantum chemical calculations used for the conformational analysis yielded two stable twist conformers, which were described using the Cremer–Pople notation for five-membered rings. The experimental spectrum of the more stable conformer with the methyl group in equatorial position was assigned and fitted using a rigid rotor model with centrifugal distortion corrections. The spectra of all five 13C-isotopologues could be observed in natural abundance. The carbon atom structure was experimentally deduced using Kraitchman’s equations and compared with the structure calculated by quantum chemistry.

Profiling C4N radicals of astrophysical interest

ABSTRACT Based on a theoretical study of neutral, anion, and cation $\text{C}_{4}\text{N}$ chains, we suggest that this molecular species can still be observed in space. We analyse the dependence on n of the enthalpies of formation across the $\text{C}_{{{ n}}}\text{N}$ family and present possible chemical pathways of $\text{C}_{4}\text{N}$ production, which are not only exoenergetic but also barrierless. To further assist astronomical observation, we report estimates obtained at the CCSD(T) level of theory for astrophysically and astrochemically relevant properties. These include structural and chemical data, dipole moments, vibrational frequencies, rotational and centrifugal distortion constants as well as electron affinity, ionization potential, and related chemical reactivity indices. Our results indicate that anion chains can be easily detected in space than neutral chains; $\text{C}_{4}\text{N}^{-}$ possesses a smaller enthalpy of formation and a substantially larger dipole moment than $\text{C}_{4}\text{N}^{\text{0}}$.