A CASSCF/CASPT2 study on the low‐lying electronic states of the CH3SS and its cation

Song, Ming‐Xing; Zhao, Zhanzheng; Zhang, Wei; Bai, Fu‐Quan; Zhang, Hongxing; Sun, Chia‐Chung

doi:10.1002/qua.23102

Cited by 6 publications

(4 citation statements)

References 35 publications

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“…Both S and S2 products are produced in multiple electronic states, suggesting excited state dissociation processes. CASSCF/CASPT2 calculations 14 predict that the first two excited states of CH3SS lie 1.05 eV and 3.42 eV above the ground state respectively, and so are not likely to contribute to the absorption at 248 nm (5.00 eV) and 193 nm (6.42 eV).…”

Section: Introductionmentioning

confidence: 99%

Photodissociation Dynamics of the Tert-Butyl Perthiyl Radical

Nichols¹,

Sullivan

Neumark³

2020

Preprint

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The photodissociation dynamics of the tert-butyl perthiyl (t-BuSS) radical are investigated by fast-beam coincidence translational spectroscopy. A fast (6-8 keV) beam of neutral t-BuSS radicals is produced via photodetachment of the corresponding anion, followed by photodissociation at 248 nm (5.00 eV) or 193 nm (6.42 eV) and coincident detection of the neutral products. Photofragment mass and translational energy distributions are obtained at both wavelengths. At 248 nm, the dominant product channel (90%) is found to be S loss, with a product translational energy distribution that peaks close to the maximum available energy and an anisotropic photofragment angular distribution, indicating dissociation along a repulsive excited state. A minor channel (10%) leading to the formation of S2 + t-Bu is also observed. At 193 nm, both two- and three-body dissociation are observed. Formation of S2 + t-Bu is the dominant two-body product channel, with multiple electronic states of the S2 molecule produced via excited state dissociation processes. Formation of S + t-BuS is a minor two-body channel at this dissociation energy. The three-body channels are S2 + H + isobutene, S2 + CH3 + propene, and S + SH + isobutene. The first two of these channels result from a sequential dissociation process in which loss of S2 from t-BuSS results in ground state t-Bu with sufficient internal energy to undergo secondary fragmentation. The third three-body channel, S + SH + isobutene, is attributed to loss of internally excited HS2 from t-BuSS, which then rapidly dissociates to form S + SH in an asynchronous concerted dissociation process.

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Section: Introductionmentioning

confidence: 99%

Photodissociation Dynamics of the Tert-Butyl Perthiyl Radical

Nichols¹,

Sullivan

Neumark³

2020

Preprint

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“…29 An S 2 loss pathway has been observed in the photodissociation of the tert-butyl perthiyl radical at 365 nm using EPR spectroscopy in a hydrocarbon matrix. 35 Recent theoretical work has explored electronic excitation of the methyl perthiyl radical, 22 finding two doublet states at 1.176 eV (1 2 A′) and 3.422 eV (2 2 A″) above the ground state. A bound quartet state (1 4 A″) was also found at 4.216 eV with dramatic elongation of the S−S bond.…”

Section: Introductionmentioning

confidence: 99%

“…The electronic ground state of the methyl perthiyl radical is the X̃ 2 A″ state, in which the radical electron is delocalized over the two S atoms in a π*-like orbital. , The ultraviolet (UV) absorption spectrum of CH 3 SS has not been experimentally characterized, though spectra of HS 2 and tert -butyl perthiyl radicals have been measured to ∼320 nm with intensity maxima around 340–370 nm. , Ionization energies and electron affinities of the methyl perthiyl radical have been characterized experimentally − and theoretically. ,,− …”

Section: Introductionmentioning

confidence: 99%

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Production and Photodissociation of the Methyl Perthiyl Radical

et al. 2016

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The photodissociation dynamics of the methyl perthiyl (CH3SS) radical are investigated via molecular beam photofragment translational spectroscopy, using "soft" electron ionization to detect the radicals and their photofragments. With this new capability, we have shown that CH3SS can be generated from flash pyrolysis of dimethyl trisulfide. Utilizing this source of radicals and the advantages afforded by soft electron ionization, we have reinvestigated the photodissociation dynamics of CH3SS at 248 nm, finding CH3S + S to be the dominant dissociation channel with CH3 + SS as a minor process. These results differ from previous work reported in our laboratory in which we found CH3 + SS and CH2S + SH as the main dissociation channels. The difference in results is discussed in light of our new capabilities for characterization of radical production.

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Kinetics investigation of the hydrogen abstraction reaction between CH3SS and CN radicals

et al. 2016

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The reaction mechanisms and rates for the H abstraction reactions between CH3SS and CN radicals in the gas phase were investigated with density functional theory (DFT) methods. The geometries, harmonic vibrational frequencies, and energies of all stationary points were obtained at B3PW91/6-311G(d,p) level of theory. Relationships between the reactants, intermediates, transition states and products were confirmed, with the frequency and the intrinsic reaction coordinate (IRC) analysis at the same theoretical level. High accurate energy information was provided by the G3(MP2) method combined with the standard statistical thermodynamics. Gibbs free energies at 298.15 K for all of the reaction steps were reported, and were used to describe the profile diagrams of the potential energy surface. The rate constants were evaluated with both the classical transition state theory and the canonical variational transition state theory, in which the small-curvature tunneling correction was included. A total number of 9 intermediates (IMs) and 17 transition states (TSs) were obtained. It is shown that IM1 is the most stable intermediate by the largest energy release, and the channel of CH3SS + CN → IM3 → TS10 → P1(CH2SS + HCN) is the dominant reaction with the lowest energy barrier of 144.7 kJ mol(-1). The fitted Arrhenius expressions of the calculated CVT/SCT rate constants for the rate-determining step of the favorable channel is k =7.73 × 10(6) T (1.40)exp(-14,423.8/T) s(-1) in the temperature range of 200-2000 K. The apparent activation energy E a(app.) for the main channel is -102.5 kJ mol(-1), which is comparable with the G3(MP2) energy barrier of -91.8 kJ mol(-1) of TS10 (relative to the reactants).

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A CASSCF/CASPT2 study on the low‐lying electronic states of the CH₃SS and its cation

Abstract: ABSTRACT:Complete active space self-consistent field (CASSCF) and multiconfiguration second-order perturbation theory (CASPT2) calculations with contracted ANO-RCC basis set were performed for low-lying electronic states of CH 3 SS and its cation in C s symmetry. For the ground state X 2

Cited by 6 publications

References 35 publications

Photodissociation Dynamics of the Tert-Butyl Perthiyl Radical

Photodissociation Dynamics of the Tert-Butyl Perthiyl Radical

Production and Photodissociation of the Methyl Perthiyl Radical

Kinetics investigation of the hydrogen abstraction reaction between CH3SS and CN radicals

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