explicitly correlated
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Matthew Beutel ◽  
Alexander Ahrens ◽  
Chenhang Huang ◽  
Yasuyuki Suzuki ◽  
Kalman Varga

Christian Balança ◽  
Ernesto Quintas-Sánchez ◽  
Richard Dawes ◽  
Fabien Dumouchel ◽  
François Lique ◽  

Abstract Carbon-chain anions were recently detected in the interstellar medium. These very reactive species are used as tracers of the physical and chemical conditions in a variety of astrophysical environments. However, the Local Thermodynamical Equilibrium conditions are generally not fulfilled in these environments. Therefore, collisional as well as radiative rates are needed to accurately model the observed emission lines. We determine in this work the state-to-state rate coefficients of C4H− in collision with both ortho- and para-H2. A new ab initio 4D potential energy surface was computed using explicitly-correlated coupled cluster procedures. This surface was then employed to determine rotational excitation and de-excitation cross sections and rate coefficients for the first 21 rotational levels (up to rotational level j1 = 20) using the close-coupling method, while the coupled-state approximation was used to extend the calculations up to j1 = 30. State-to-state rate coefficients were obtained for the temperature range 2–100 K. The differences between the ortho- and para-H2 rate coefficients are found to be small.

2021 ◽  
Vol 507 (4) ◽  
pp. 5264-5271
Manel Naouai ◽  
Abdelhak Jrad ◽  
Ayda Badri ◽  
Faouzi Najar

ABSTRACT Rotational inelastic scattering of silyl cyanide (SiH3CN) molecule with helium (He) atoms is investigated. Three-dimensional potential energy surface (3D-PES) for the SiH3CN–He interacting system is carried out. The ab initio 3D-PES is computed using explicitly correlated coupled cluster approach with single, double, and perturbative triple excitation CCSD(T)-F12a connected to augmented-correlation consistent-polarized valence triple zeta Gaussian basis set. A global minimum at (R = 6.35 bohr; θ = 90○; ϕ = 60○) with a well depth of 52.99 cm−1 is pointed out. Inelastic rotational cross-sections are emphasized for the 22 first rotational levels for total energy up to 500 cm−1 via close coupling (CC) approach in the case of A-SiH3CN and for the 24 first rotational levels for total energy up to 100 cm−1 via CC and from 100 to 500 cm−1 via coupled states (CS) in the case of E-SiH3CN. Rate coefficients are derived for temperature until 80 K for both A- and E-SiH3CN–He systems. Propensity rules are obtained for |ΔJ| = 2 processes with broken parity for A-SiH3CN and for |ΔJ| = 2 processes with |ΔK| = 0 and unbroken parity for E-SiH3CN.

2021 ◽  
Vol 155 (3) ◽  
pp. 034107
Mihály Kállay ◽  
Réka A. Horváth ◽  
László Gyevi-Nagy ◽  
Péter R. Nagy

2021 ◽  
Vol 155 (1) ◽  
pp. 014107
Denis Bokhan ◽  
Alexander S. Bednyakov ◽  
Monika Musiał ◽  
Ajith Perera ◽  
Dmitrii N. Trubnikov

2021 ◽  
Vol 154 (22) ◽  
pp. 224110
Péter Jeszenszki ◽  
Dávid Ferenc ◽  
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