Spin-orbit mechanism of predissociation in the Wulf band of ozone

Grebenshchikov, Sergy Yu.; Qu, Zheng‐Wang; Zhu, Hai‐Liang; Schinke, Reinhard

doi:10.1063/1.2219444

Cited by 12 publications

(8 citation statements)

References 23 publications

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“…The oscillator strengths estimated by the MCQR approximation for the next 3 A 2 ← X 1 A 1 and 3 B 1 ← X 1 A 1 electronic transitions are of the same order of magnitude, being 5.7 × 10 –7 and 1.3 × 10 –7 , respectively . Both of these transitions therefore contribute to the Wulf band and can be finally assigned as the 3 A 2 state mixed with the 3 B 1 state. − This pure theoretical conclusion is in good agreement with the latest experimental measurements and high-level ab initio calculations for the electronic structure: “the Wulf spectrum is a superposition of two almost independent spectra corresponding to the two diabatic electronic states, 3 A 2 and 3 B 1 ” …”

Section: Computational Phosphorescence Of Molecular Systemssupporting

confidence: 78%

Theory and Calculation of the Phosphorescence Phenomenon

2017

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Phosphorescence is a phenomenon of delayed luminescence that corresponds to the radiative decay of the molecular triplet state. As a general property of molecules, phosphorescence represents a cornerstone problem of chemical physics due to the spin prohibition of the underlying triplet-singlet emission and because its analysis embraces a deep knowledge of electronic molecular structure. Phosphorescence is the simplest physical process which provides an example of spin-forbidden transformation with a characteristic spin selectivity and magnetic field dependence, being the model also for more complicated chemical reactions and for spin catalysis applications. The bridging of the spin prohibition in phosphorescence is commonly analyzed by perturbation theory, which considers the intensity borrowing from spin-allowed electronic transitions. In this review, we highlight the basic theoretical principles and computational aspects for the estimation of various phosphorescence parameters, like intensity, radiative rate constant, lifetime, polarization, zero-field splitting, and spin sublevel population. Qualitative aspects of the phosphorescence phenomenon are discussed in terms of concepts like structure-activity relationships, donor-acceptor interactions, vibronic activity, and the role of spin-orbit coupling under charge-transfer perturbations. We illustrate the theory and principles of computational phosphorescence by highlighting studies of classical examples like molecular nitrogen and oxygen, benzene, naphthalene and their azaderivatives, porphyrins, as well as by reviewing current research on systems like electrophosphorescent transition metal complexes, nucleobases, and amino acids. We furthermore discuss modern studies of phosphorescence that cover topics of applied relevance, like the design of novel photofunctional materials for organic light-emitting diodes (OLEDs), photovoltaic cells, chemical sensors, and bioimaging.

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Section: Computational Phosphorescence Of Molecular Systemssupporting

confidence: 78%

Theory and Calculation of the Phosphorescence Phenomenon

2017

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“…The inclusion of the SOC lifts the initial degeneracy of the different spin components of the triplet states (M S ¼ 0, ± 1). Then, introducing the symmetric ( þ ) and asymmetric ( À ) combinations of states with M S ¼ ± 1, we can write the Hamiltonian including the SOC interaction in block matrix form, with (i) one block of A 0 symmetry, formed by the { 1 3 A 2 (0)} states; and (ii) one of A 00 symmetry collecting the { 1 3 A 2 ( À )} ones. It should be noted that the A 0 block includes the electronic GS ( 1 A 1 ), which lies about 3 eV below the other states in the block.…”

Section: Resultsmentioning

confidence: 99%

“…n closed-shell systems, the spin-forbidden nature of the direct transition from the singlet electronic ground state (GS) to the excited triplet states prevents the direct study of the latter. Moreover, despite the fact that their weak signal can be observed in the low-energy region of the photoabsorption spectra of many compounds [1][2][3][4] , its analysis is hindered since, at higher energies, this information is usually masked by the intense signal from the allowed transition from the GS to singlet excited states. As a result, the characterization of the triplet states using the photoabsorption spectra is, in general, not possible over an extended energy range.…”

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Direct observation of spin-forbidden transitions through the use of suitably polarized light

et al. 2014

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The study of excited triplet states of a molecular system is a difficult task because accessing them involves forbidden transitions from the singlet ground state. Nevertheless, absorption spectra of many molecules present, at low energies, the weak fingerprint of these triplet states. At higher energies this information is usually masked by the intense signal of the singlet states. Here we show, for the specific case of the sulphur dioxide molecule, that the combined use of polarized light and molecular alignment can enhance the triplet part of the spectrum, even making it the only absorption process.

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“…The 23 A"excited state is partially mixed with low-lying electronically excited states (1 3 A";1 3 A';11 A") near the repulsive region of their potentials, due to strong non-adiabatic couplings[74]. This activated complex O 3 * will subsequently decay to form an O 2 molecule in the ground electronic state, since these ozone states (1 3 A";1 3 A';1 1 A") asymptotically correlate with the O( 3 P) + O 2 (X 3 Σ) dissociation limit[74]-[76].…”

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confidence: 99%

Fast quenching of metastable O₂(a ¹Δ_g) and O₂(b ¹Σ_g ⁺) molecules by O(³P) atoms at high temperature

Volynets¹,

Lopaev²,

Рахимова³

et al. 2020

Plasma Sources Sci. Technol.

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Oxygen molecules in the lowest metastable state, O 2 (a 1  g ), play an important role in oxygen plasmas due to their high reactivity and significant concentrations. The accumulation of high densities of O 2 (a 1  g ) occurs due to its low quenching rate. This paper demonstrates the existence, at high gas temperatures (700-1700K), of fast quenching of O 2 (a 1  g ) by O( 3 P) atoms, a process that has not been considered in previous models. Experiments were carried out at oxygen pressures of 10-100Torr in an 81MHz CCP discharge in a quartz tube with external electrodes. This setup provides high absorbed power density, leading to both high gas temperatures and significant O( 3 P) densities. We observe that the O 2 (a 1  g ) density is significantly limited at high gas temperatures by rapid quenching by atomic oxygen . The results were interpreted using a self-consistent 1D discharge model. The observations can only be explained by the inclusion of a rapid quenching, with an activation energy in the range of 0.54-0.69eV. The rate constant was determined over a wide range of discharge conditions (P = 20-100 Torr and T g = 800-1700 K), giving values between 3•10 -11 ×exp(-8000/T) cm 3 /s to 1.5•10 -11 ×exp(-6300/T) cm 3 /s. A possible mechanism for this process is discussed. Measurements of the density of metastable O 2 (b 1  g + ) molecules also indicated the existence of quenching by atomic oxygen, with a somewhat lower activation energy of ~0.32 eV. The variations of the measured [O 2 (b 1  g + )]/N molefraction could be fitted by the model using a rate constant -210 -11 exp(-3700/T) cm 3 /s for this process. These quenching processes of metastable O 2 (a 1  g ) and O 2 (b 1  g + ) molecules by oxygen atoms are important for oxygen plasmas and could have a significant impact on the kinetics of oxygen-containing mixtures at higher gas temperatures, for example in plasma-assisted combustion or in high-pressure plasma processing reactors.

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Spin-orbit mechanism of predissociation in the Wulf band of ozone

Cited by 12 publications

References 23 publications

Theory and Calculation of the Phosphorescence Phenomenon

Theory and Calculation of the Phosphorescence Phenomenon

Direct observation of spin-forbidden transitions through the use of suitably polarized light

Fast quenching of metastable O₂(a ¹Δ_g) and O₂(b ¹Σ_g ⁺) molecules by O(³P) atoms at high temperature

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Spin-orbit mechanism of predissociation in the Wulf band of ozone

Cited by 12 publications

References 23 publications

Theory and Calculation of the Phosphorescence Phenomenon

Theory and Calculation of the Phosphorescence Phenomenon

Direct observation of spin-forbidden transitions through the use of suitably polarized light

Fast quenching of metastable O2(a 1Δ g ) and O2(b 1Σ g +) molecules by O(3P) atoms at high temperature

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Product

Resources

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Fast quenching of metastable O₂(a ¹Δ_g) and O₂(b ¹Σ_g ⁺) molecules by O(³P) atoms at high temperature