A theoretical study on photodissociation of the A state of the H2S+ ion

作者：Chang Hai Bo; Huang Ming Bao^*

来源：Theoretical Chemistry Accounts, 2009, 122(3-4): 189-196.

DOI：10.1007/s00214-008-0498-4

• H2S+ ion
• CASPT2
• Photodissociation

We have studied photodissociation of the A state of the H2S+ ion using the quantum-chemical CAS methods, and the 1(2) A '' (X-2 B-1) and 1(4) A '' states are involved in photodissociation of the 1(2) 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 1(2) A '' and 1(2) A' states correlate with the second limit [H-2 + S+(D-2)] while the 1(4) A '' state correlates with the first limit [H-2 + S+(S-4)] and that there are a transition state and a local minimum along the 1(2) A' PEC and the repulsive 1(4) A '' PEC crosses the 1(2) A '' and 1(2) A' PECs. The CASPT2 H-loss dissociation PEC calculations indicate that the 1(2) A '' and 1(4) A '' states correlate with the first limit [HS+(X-3 Sigma(-))+ H] while the 1(2) A' state correlates with the second limit [HS+(a(1) Delta) + H] and that the repulsive 1(4) A '' PEC crosses the 1(2) 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) (1(2) A') (2.38 eV) -> barrier at the linearity (2.96 eV) -> X-2 B-1 (1(2) A '') (0.0 eV) -> the 1(2) A ''/1(4) A '' MECP (3.50 eV, large spin-orbit coupling) -> H-2(X-1 Sigma(+)(g)) + S+ (S-4) ( 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).

• 出版日期2009-3
• 单位中国科学院