Abstract
We have studied photodissociation of the A state of the H2S+ ion using the quantum-chemical CAS methods, and the 12 A″ (X 2 B 1) and 14 A″ states are involved in photodissociation of the 12 A′ (A 2 A 1) state (the electronic states in dissociation were studied in the C s symmetry). The CASPT2 S-loss dissociation potential energy curve (PEC) calculations indicate that the 12 A″ and 12 A′ states correlate with the second limit [H2 + S+(2 D)] while the 14 A″ state correlates with the first limit [H2 + S+(4S)] and that there are a transition state and a local minimum along the 12 A′ PEC and the repulsive 14 A″ PEC crosses the 12 A″ and 12 A′ PECs. The CASPT2 H-loss dissociation PEC calculations indicate that the 12 A″ and 14 A″ states correlate with the first limit [HS+(X 3Σ−) + H] while the 12 A′ state correlates with the second limit [HS+(a 1Δ) + H] and that the repulsive 14 A″ PEC crosses the 12 A′ PEC. For the crossing doublet and quartet states in pairs, we performed CASSCF minimum energy crossing point (MECP) calculations, and the CASSCF spin-orbit couplings and CASPT2 energies at the MECP geometries were calculated. We examined the two previously proposed mechanisms (mechanisms I and II) for dissociation of the A state to the S+ ion, based on our calculation results. We suggest processes for dissociation of the A state to the S+ ion (processes I and II, based on mechanisms I and II, respectively) and to the SH+ ion (process III) and conclude that photodissociation of the A state mainly leads to the S+ ion via the most energetically favorable process II: A 2 A 1 (12 A′) (2.38 eV) → barrier at the linearity (2.96 eV) → X 2 B 1 (12 A″) (0.0 eV) → the 12 A″/14 A″ MECP (3.50 eV, large spin-orbit coupling) → H2 \( (X^{ 1} \Upsigma_{\text{g}}^{ + } ) \) + S+(4S) (2.92 eV) (the CASPT2 relative energy values to X 2 B 1 are given in parentheses and the largest value is 3.50 eV at the MECP).
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We appreciate the financial support of this work that was provided by National Natural Science Foundation of China through Contract No. 20773161.
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Chang, HB., Huang, MB. A theoretical study on photodissociation of the A state of the H2S+ ion. Theor Chem Account 122, 189–196 (2009). https://doi.org/10.1007/s00214-008-0498-4
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DOI: https://doi.org/10.1007/s00214-008-0498-4