A combined theoretical treatment of T1→S intersystem crossing and intramolecular vibrational redistribution in thiophosgene

Rashev, S.; Moule, D. C.

doi:10.1063/1.2888172

Cited by 10 publications

(9 citation statements)

References 12 publications

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“…As we have already pointed out in our previous work14, 16, the vibrational level density of S 0 Cl2CS is rather sparse at the vibrational excitation energies of ∼17,500 cm −1 . The resultant rovibrational level density even for J = 10 is still insufficient for a truly dissipative nonradiative ISC process S 0 ← T 1 to take place.…”

Section: Results and Conclusionsupporting

confidence: 57%

Section: Introductionmentioning

confidence: 99%

“…In recent years, we have performed a series of theoretical studies on the ISC process in thiophosgene14–16. Initially, we performed a model calculation of the ISC rate constant K ISC , using a modified Fermi golden rule expression14. The explicit calculation of spin–orbit (SO) coupling matrix elements between the initial T 1 level $|s\rangle$ and isoenergetic, highly vibrationally excited S 0 levels $|l_{k}\rangle$ was based on an analysis of the vibrational structure of the ground electronic state8, in terms of symmetrized vibrational coordinates16.…”

Section: Introductionmentioning

confidence: 99%

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The role of rotational relaxation in the intersystem crossing between a triplet and a singlet electronic state

Rashev

Moule

Judge

2010

Int J of Quantum Chemistry

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A calculation of the rate of ISC (intersystem crossing) relaxation at 0 K requires a knowledge of the spin-orbit coupling and the vibrational overlap integrals (Franck-Condon factors) between the T 1 and S 0 states. At elevated temperatures, the population of the rotational states needs to be taken into account through the overlap of the rotational wavefunctions between the interacting T 1 /S 0 electronic states. Here, we discuss the effect of the ISC singlet-triplet selection rules on the number and magnitude of the rotational overlap factors for the J ¼ 0, 5, and 10 rotational levels of thiophosgene, Cl 2 CS. Of equal importance is the influence of the spin-spin and spinrotation coupling on the rotational fragmentation factors and the ISC survival probability.

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Section: Results and Conclusionsupporting

confidence: 57%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The role of rotational relaxation in the intersystem crossing between a triplet and a singlet electronic state

Rashev

Moule

Judge

2010

Int J of Quantum Chemistry

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“…41 There have been several attempts for over 20 years to develop a quantitative theory for the spin crossover of thiophosgene. [36][37][38][42][43][44][45] The development of accurate nonadiabatic rate theories is an active field of research itself and various approaches have been tried.…”

Section: Introductionmentioning

confidence: 99%

Spin crossover of thiophosgene via multidimensional heavy-atom quantum tunneling

Heller

Richardson

2021

Preprint

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The spin-crossover reaction of thiophosgene has drawn broad attention from both experimenters and theoreticians as a prime example of radiationless intramolecular decay via intersystem crossing. Despite multiple attempts over 20 years, theoretical predictions have typically been orders of magnitude in error relative to the experimentally measured triplet lifetime. We address the T1 → S0 transition by the first application of semiclassical golden-rule instanton theory in conjunction with on-the-fly electronic-structure calculations based on multireference perturbation theory. Our first-principles approach provides excellent agreement with the experimental rates. This was only possible due to the fact that instanton theory goes beyond previous methods by locating the optimal tunneling pathway in full dimensionality and thus captures "corner cutting" effects. Since the reaction is situated in the Marcus inverted regime, the tunneling mechanism can be interpreted in terms of two classical trajectories, one traveling forwards and one backwards in imaginary time, which are connected by particle--antiparticle creation and annihilation events. The calculated mechanism indicates that the spin crossover is sped up by many orders of magnitude due to multidimensional quantum tunneling of the carbon atom even at room temperature.

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“…Nevertheless, as will be seen below, even this reduced system presents a stiff challenge with regards to the dynamical assignments of the highly excited eigenstates. The IVR dynamics in SCCl 2 has been the subject of several recent experimental [7][8][9] and theoretical [10][11][12] studies. In an early detailed study, Strickler and Gruebele established [7] that the IVR state space (zeroth-order quantum number space) has an effective dimensionality of three as opposed to the theoretically possible six.…”

Section: Introducionmentioning

confidence: 99%

On the nature of highly vibrationally excited states of thiophosgene#

Keshavamurthy

2012

J Chem Sci

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In this work an analysis of the highly vibrationally excited states of thiophosgene (SCCl2) is made in order to gain insights into some of the experimental observations and spectral features. The states analyzed herein lie in a spectrally complex region where strong mode mixings are expected due to the overlap of several strong anharmonic Fermi resonances. Two recent techniques, a semiclassical angle space representation of the eigenstates and the parametric variation of the eigenvalues (levelvelocities) are used to identify eigenstate sequences exhibiting common localization characteristics. Preliminary results on the influence of highly excited out-of-plane bending modes on the nature of the eigenstates suggest a possible bifurcation in the system. I. INTRODUCIONUnderstanding the nature of the highly excited molecular eigenstates is equivalent to deciphering the mechanism of intramolecular vibrational energy redistribution (IVR) occuring in the molecule [1]. However, the assignment of eigenstates is far from simple. The existence of and interplay of several strong anharmonic resonances result in complicated spectral patterns and highly mixed states. Nevertheless, eigenstates of molecular systems rarely exhibit the extreme scenario of being completely ergodic or completely regular [2]. A generic situation, even at fairly high energies, is the coexistence of several classes of eigenstates with differing degree of mixing being interspersed among each other [3,4]. More interestingly, the interspersed states can show several sequences associated with certain identifiable common localization characteristics. In other words, although a full set of quantum numbers do not exist for labeling such states, there are reasons to believe that a sufficient number of approximate quantum numbers do exist to understand, and hence assign, the eigenstates. Since the approximate quantum numbers arise out of the local dynamics due to specific resonances, relevant at the energies of interest, the assignment is inherently dynamical in nature. In a nutshell, several decades of work have shown that dynamical assignments can be done reliably only if the structure of the corresponding classical phase space is well understood [5].This work is concerned with the dynamical assignment of the eigenstates of thiophosgene SCCl 2 . The Hamiltonian of interest is a highly accurate spectroscopic Hamiltonian obtained [6] by Gruebele and Sibert via a canonical Van Vleck perturbation analysis of the experimentally derived normal mode potential surface [7]. The Hamiltonian can be expressed as H = H 0 + V res withThe zeroth-order anharmonic Hamiltonian is H 0 , whose eigenstates are the feature states and V res accounts for the important anharmonic resonances responsible for the IVR dynamics. In the rest of the paper the various resonances will be refered to by simply indicating the modes. For instance, the first resonance term in V res above will be refered to as the 526-resonance. The hermitian adjoints of the operators are denoted by c.c., and the op...

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A combined theoretical treatment of T1→S intersystem crossing and intramolecular vibrational redistribution in thiophosgene

Cited by 10 publications

References 12 publications

The role of rotational relaxation in the intersystem crossing between a triplet and a singlet electronic state

The role of rotational relaxation in the intersystem crossing between a triplet and a singlet electronic state

Spin crossover of thiophosgene via multidimensional heavy-atom quantum tunneling

On the nature of highly vibrationally excited states of thiophosgene#

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