scholarly journals Investigation of the spin-forbidden process in thymine

2012 ◽  
Vol 66 (2) ◽  
pp. 165-170
Author(s):  
Mihajlo Etinski
Keyword(s):  
Correlation Function ◽  
Energy Gap ◽  
Harmonic Approximation ◽  
Normal Modes ◽  
Electronic States ◽  
Nuclear Motion ◽  
Intersystem Crossing ◽  
Condon Approximation ◽  
Adiabatic Energy ◽  
Mode Mixing

The intersystem crossing rate from the lowest singlet to the lowest triplet state of thymine was studied by means of the ab initio methods. The rate was calculated employing the time-dependent approach based on the correlation function. The normal modes of the singlet and triplet electronic states are related by the Duschinsky transformation, i. e. by rotation and translation. The correlation function was calculated using the Condon approximation for the spin-orbit matrix element and harmonic approximation for the nuclear motion. The intersystem crossing rate strongly depends on the singlet-triplet adiabatic energy gap and on the normal mode mixing.

scholarly journals Effect of temperature on rate of the spin-forbidden transition in uracil and thymine

2013 ◽  
Vol 78 (1) ◽  
pp. 65-73 ◽  
Author(s):  
Mihajlo Etinski
Keyword(s):  
Correlation Function ◽  
Vibrational Energy ◽  
Energy Gap ◽  
Excited Electronic State ◽  
Harmonic Approximation ◽  
Normal Modes ◽  
Heat Bath ◽  
Effect Of Temperature ◽  
Condon Approximation ◽  
Triplet Formation

The intersystem crossing rates of uracil and thymine molecules in interaction with the heat bath were studied by means of the ab initio methods. The rates were calculated employing the time-dependent approach based on the correlation function. The normal modes of the singlet and triplet electronic states were related by the Duschinsky transformation. The correlation function was calculated using the Condon approximation for the spin-orbit matrix element and harmonic approximation for the nuclear motion. The excess vibrational energy in the initial singlet excited electronic state decreases the rate of the triplet formation in uracil and thymine. This decrease is more pronounced for uracil. Also, it was found that the change of the adiabatic energy gap can significantly modify the rate of the triplet formation.

scholarly journals The role of Duschinsky rotation in intersystem crossing: A case study of uracil

2011 ◽  
Vol 76 (12) ◽  
pp. 1649-1660 ◽  
Author(s):  
Mihajlo Etinski
Keyword(s):  
Correlation Function ◽  
Normal Modes ◽  
Intersystem Crossing ◽  
Triplet States ◽  
Cumulant Expansion ◽  
Time Approximation ◽  
Energy Gaps ◽  
Singlet And Triplet States ◽  
Quantitative Results ◽  
Short Time

The intersystem crossing rate for the transition between the lowest excited singlet and triplet electronic states of uracil was studied by means of ab initio methods. The rate was evaluated using the timedependent approach based on the correlation function and its two approximations: the second-order cumulant expansion and the short-time approximation. The normal modes of the singlet and triplet states are related by the Duschinsky transformation, i.e., by rotation and translation. It was found that for singlet-triplet adiabatic energy gaps below 6000 cm-1, the inclusion of the Duschinsky rotation is necessary for quantitative results. Above energy gaps of 6000 cm-1, the rates obtained with and without the Duschinsky rotation are similar. The cumulant expansion approximates well the correlation function. The short-time approximation, although crude, can be used as the first estimate of the rate.

The influence of spin–orbit coupling, Duschinsky rotation and displacement vector on the rate of intersystem crossing of benzophenone and its fused analog fluorenone: a time dependent correlation function based approach

2020 ◽  
Vol 22 (42) ◽  
pp. 24399-24409
Author(s):  
Pijush Karak ◽  
Swapan Chakrabarti
Keyword(s):  
Correlation Function ◽  
Displacement Vector ◽  
Orbit Coupling ◽  
Time Dependent ◽  
Intersystem Crossing ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Complex Combination ◽  
Dependent Correlation ◽  
Mode Mixing

A time dependent correlation function based study reveals that the rate of intersystem crossing of benzophenone and its fused analog, fluorenone is governed by a complex combination of spin–orbit coupling, displacements and Duschinsky mode mixing.

Triatomic molecules

2018 ◽  
Author(s):  
John H. D. Eland ◽  
Raimund Feifel
Keyword(s):  
Degrees Of Freedom ◽  
Normal Modes ◽  
Electronic States ◽  
Triatomic Molecules ◽  
Doubly Charged Ions ◽  
Spectral Bands ◽  
Valence Electrons ◽  
Doubly Charged ◽  
Charged Ions ◽  
Double Ionisation

Double ionisation of the triatomic molecules presented in this chapter shows an added degree of complexity. Besides potentially having many more electrons, they have three vibrational degrees of freedom (three normal modes) instead of the single one in a diatomic molecule. For asymmetric and bent triatomic molecules multiple modes can be excited, so the spectral bands may be congested in all forms of electronic spectra, including double ionisation. Double photoionisation spectra of H2O, H2S, HCN, CO2, N2O, OCS, CS2, BrCN, ICN, HgCl2, NO2, and SO2 are presented with analysis to identify the electronic states of the doubly charged ions. The order of the molecules in this chapter is set first by the number of valence electrons, then by the molecular weight.

scholarly journals Modeling nonadiabatic dynamics with degenerate electronic states, intersystem crossing, and spin separation: A key goal for chemical physics

2021 ◽  
Vol 154 (11) ◽  
pp. 110901
Author(s):  
Xuezhi Bian ◽  
Yanze Wu ◽  
Hung-Hsuan Teh ◽  
Zeyu Zhou ◽  
Hsing-Ta Chen ◽  
...  
Keyword(s):  
Electronic States ◽  
Intersystem Crossing ◽  
Chemical Physics ◽  
Nonadiabatic Dynamics

The Energy Band Structure of Polyacene with Soliton Excitation

1997 ◽  
Vol 11 (11) ◽  
pp. 477-483 ◽  
Author(s):  
Z. J. Li ◽  
H. B. Xu ◽  
K. L. Yao
Keyword(s):  
Band Structure ◽  
Charge Density ◽  
Energy Band ◽  
Energy Gap ◽  
Electronic States ◽  
Energy Band Structure ◽  
Energy Spectra ◽  
Energy Band Gap ◽  
The One ◽  
Soliton Excitation

Starting from the extensional Su–Schrieffer–Heeger model taking into account the effects of interchain coupling, we have studied the energy spectra and electronic states of soliton excitation in polyacene. The dimerized displacement u0 is found to be similar to the case of trans-polyacetylene, and equals to 0.04 Å. The energy-band gap is 0.38 eV, in agreement with the results derived by other authors. Two new bound electronic states have been found in the conduction band and in the valence band, which is different from the one of trans-polyacetylene. There exists two degenerate soliton states in the center of energy gap. Furthermore, the distribution of charge density and spin density have been discussed in detail.

Tailoring plasmon excitations in α − T3 armchair nanoribbons

2021 ◽  
Author(s):  
Andrii Iurov ◽  
Liubov Zhemchuzhna ◽  
Godfrey Gumbs ◽  
Danhong Huang ◽  
Paula Fekete ◽  
...  
Keyword(s):  
Energy Gap ◽  
Graphene Nanoribbons ◽  
Electronic States ◽  
Landau Damping ◽  
Next Generation ◽  
Polarization Function ◽  
Edge Termination

Abstract We have calculated and investigated the electronic states, dynamical polarization function and the plasmon excitations for α − T3 nanoribbons with armchair-edge termination. The obtained plasmon dispersions are found to depend significantly on the number of atomic rows across the ribbon and the energy gap which is also determined by the nanoribbon geometry. The bandgap appears to have the strongest effect on both the plasmon dispersions and their Landau damping. We have determined the conditions when relative hopping parameter α of an α − T3 lattice has a strong effect on the plasmons which makes our material distinguished from graphene nanoribbons. Our results for the electronic and collective properties of α − T3 nanoribbons are expected to find numerous applications in the development of the next-generation electronic, nano-optical and plasmonic devices.

Effects of Pressure and Temperature on the Fluorescence Quantum Yield of N-Methylacridone in Solution Interpreted in Terms of the Eyring Transition-StateTheory

1981 ◽  
Vol 36 (5) ◽  
pp. 489-493
Author(s):  
H.-D. Brauer ◽  
R. Schmidt ◽  
B. Hammerich
Keyword(s):  
Quantum Yield ◽  
Fluorescence Quantum Yield ◽  
Energy Gap ◽  
State Theory ◽  
Intersystem Crossing ◽  
Thermally Activated ◽  
Elevated Pressures ◽  
Condon Factors ◽  
Positive Volume ◽  
Franck Condon

Abstract The influence of temperatur and pressure on the fluorescence quantum yield of N-methylacridone (9,10-dihydro-9-oxo-10-methyl-acridine) in toluene in the range of 283-313 K and 1 bar to 2.5 kbar, respectively, has been investigated. Treatment of the data in terms of the Eyring transition-state theory leads to a consistent interpretation of the observed effect. The unusually large increase of the quantum yield with increasing pressure is attributed to a positive volume of activation, ⊿V≠, for the thermally activated S1-T2 intersystem crossing which is known to be the only deactivation process (of the Si-state) competing with fluorescence. Comparison of the values for ⊿H≠, the activation enthalpy of this process, determined at various pressures, indicates a decrease in ⊿H≠ at elevated pressures. Since ⊿H≠ can be associated with the S1-T2 energy gap involved in intersystem crossing, this result further confirms the conclusion that the change in Franck-Condon factors alone cannot account for the decrease in the intersystem crossing rate with increasing pressure.

Aggregation-induced emission (AIE)-active molecules bearing singlet oxygen generation activities: the tunable singlet–triplet energy gap matters

2019 ◽  
Vol 55 (10) ◽  
pp. 1450-1453 ◽  
Author(s):  
Chengkai Zhang ◽  
Yanqian Zhao ◽  
Dandan Li ◽  
Jiejie Liu ◽  
Heguo Han ◽  
...  
Keyword(s):  
Singlet Oxygen ◽  
Cell Apoptosis ◽  
Near Infrared ◽  
Energy Gap ◽  
Intersystem Crossing ◽  
Triplet Energy ◽  
Oxygen Generation ◽  
Two Photon ◽  
Singlet Oxygen Generation ◽  
Infrared Excitation

Two-photon active photosensitizers showed relatively strong intersystem crossing facilitating 1O2 generation and cell apoptosis with near-infrared excitation.

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