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[en] Highlights: • Multipath VTST rate constants for methyl formate hydrogen abstraction by deuterium. • The multistructural torsional anharmonicity factor change considerably k(T). • The path-averaged generalized transmission coefficient is dominated by the path 1. • Multidimensional tunneling plays an essential role at low temperatures. The thermal rate constants for the methyl formate hydrogen abstraction reaction by deuterium was investigated by the multipath canonical variational transition state theory with large curvature tunneling (MP-CVT/LCT). The multistructural torsional anharmonicity factor decreases the thermal rate constants for deuterated reaction R1a and increases considerably for R2a. The path-averaged generalized transmission coefficient is dominated by the characteristics of the lowest-energy paths for both reactions. The MP-CVT/LCT rate constants are in excellent agreement with experimental data (T = 1079–1270 K).

[en] Highlights: • New chalcogen-halogen diatomics. • Reliable characterization of excited electronic states including spin-orbit effects. • Should help plan and guide future experimental investigations. • Transition moments, transition probabilities, radiative lifetimes. A new species, selenium monoiodide (SeI), was investigated for the first time at a high level of theoretical approach, SA-CASSCF/MRCI. The overall picture of all doublet and quartet (Λ + S) states correlating with the three lowest dissociation channels and the associated Ω states provide reliable results to help understand the lack of experimental data on its transitions and to plan the investigation and determination of spectroscopic parameters. Transition probabilities were computed for the transitions X₂ – X₁, A₁ – X₁, A₂ – X₁, and A₂ – X₂, originated from the spin-forbidden 1 ⁴Σ⁻ - X ²Π system, and the corresponding radiative lifetimes evaluated.

[en] Highlights: • Metastability of the low-lying electronic states of CBr²⁺. • Characterization of ground and excited states including spin-orbit effects. • Adiabatic ionization energies. • Tunneling widths and lifetimes. The metastability of the low-lying electronic states of CBr²⁺ correlating with the two lowest dissociation channels was investigated for the first time at a high level theoretical approach, SA-CASSCF/MRCI. Spin-orbit interaction changes substantially the profile of the potential energy curves, specially for the ground (X ${}^2{\mathrm{\Sigma }}^{+}$) and first excited (1 ${}^2\mathrm{\Pi }$) states. The second adiabatic ionization energies are also determined and show an excelent agreement with the experimental derived values. Tunneling widths computed for the $\mathrm{\Omega }$ bound states show that the lowest vibrational levels of components 1/2 are stable against tunneling.

[en] Highlights: • First reliable characterization of potential energy curves of CI cation. • Characterization of the low-lying electronic states of CI. • Transition moments, transition probabilities, and radiative lifetimes. • Simulated single ionization spectrum of CI. We present a theoretical characterization of the cation iodocarbyne, CI⁺, using a correlated theoretical approach (SA-CASSCF/MRCI) to describe a manifold of singlet, triplet, and quintet electronic states. Reliable potential energy curves were constructed for both $\mathrm{\Lambda }$+S and relativistic $\mathrm{\Omega }$ states. Spin–orbit couplings strongly affect the energetic profile of the $\mathrm{\Lambda }$+S representation. Spectroscopic parameters were calculated, and effects of core-valence correlation investigated. The transition dipole moment functions for the 1₁ ³${\mathrm{\Pi }}_{0^{+}}$ $\to$ X₁ ¹${\mathrm{\Sigma }}_{0^{+}}^{+}$ and 1₃ ³${\mathrm{\Pi }}_1$ $\to$ X₁ ¹${\mathrm{\Sigma }}_{0^{+}}^{+}$ states were evaluated and the corresponding radiative lifetimes obtained. Comparisons with other halocarbynes can now help understanding trends in properties in this class of molecules.