Vibronic-coupling effect on the paramagneticFe2+ions in an insulator: Mössbauer quadrupole splitting in a biological system

1992 ◽  
Vol 46 (2) ◽  
pp. 632-638 ◽  
Author(s):  
T. P. Sinha
Keyword(s):  
Quadrupole Splitting ◽  
Biological System ◽  
Coupling Effect ◽  
Vibronic Coupling

Theoretical and Experimental Investigations on the Aggregation‐Enhanced Emission from Dark State: Vibronic Coupling Effect

2020 ◽  
Vol 6 (7) ◽  
pp. 2000255
Author(s):  
Ping‐An Yin ◽  
Qing Wan ◽  
Yingli Niu ◽  
Qian Peng ◽  
Zhiming Wang ◽  
...  
Keyword(s):  
Coupling Effect ◽  
Vibronic Coupling ◽  
Experimental Investigations ◽  
Dark State

scholarly journals Vibronic Effects in Mossbauer Spectra: The 57Fe Quadrupole Splitting in FeCO3

1978 ◽  
Vol 31 (5) ◽  
pp. 397 ◽  
Author(s):  
DC Price
Keyword(s):  
Quadrupole Splitting ◽  
Lattice Relaxation ◽  
Vibronic Coupling ◽  
Spin Lattice Relaxation ◽  
Relaxation Rates ◽  
Temperature Dependent ◽  
Spin Lattice ◽  
Symmetry Properties ◽  
Coupling Parameters ◽  
Magnetic Ions

The methods developed by Orbach and coworkers for calculating spin-lattice relaxation rates have been generalized to enable calculation of the effects of vibronic admixture between low-lying electronic states on observables, such as the Mossbauer quadrupole splitting, associated with magnetic ions in crystals. Emphasis is placed on the need to take proper account of the symmetry properties of the phonons until a late stage in the calculation. Application is made to the temperature dependence of the 57Fe quadrupole splitting in FeC03 , and it is concluded that, in general, vibronic coupling effects must be considered before static splitting parameters are extracted from experimental data relating to the temperature-dependent populations of electronic levels. The superposition model of the crystal field is employed to estimate the vibronic coupling parameters.

MÖSSBAUER QUADRUPOLE SPLITTING of Fe2+ in NH4CoCl3 UNDER ORBIT–LATTICE INTERACTION

2001 ◽  
Vol 15 (32) ◽  
pp. 4223-4229
Author(s):  
T. P. SINHA
Keyword(s):  
Experimental Data ◽  
Temperature Dependence ◽  
Quadrupole Splitting ◽  
Charge Distribution ◽  
Vibronic Coupling ◽  
Electronic Charge ◽  
Thermal Modulation ◽  
Electronic Charge Distribution ◽  
Dynamical Parameters ◽  
Good Agreement

The effect of orbit–lattice interaction (vibronic coupling) has been considered to explain the observed temperature dependence of Mössbauer quadrupole splitting of Fe2+ ions in NH4CoCl3 over 27 to 250 K. The orbit–lattice interaction accounts for the thermal modulation of the electronic charge distribution of Fe2+ due to vibration of the surrounding ligands. The various lattice dynamical parameters are estimated and then quadrupole splitting is explicitly calculated as a function of temperature. One obtains a reasonably good agreement with the experimental data which shows that the vibronic coupling is quite realistic and important.

scholarly journals Herzberg-Teller Vibronic Coupling Effect on the Vibrationally-Resolved Electronic Spectra and Intersystem Crossing Rates of a TADF Emitter: 7-PhQAD

2021 ◽  
Author(s):  
Sirong Lin ◽  
Zheng Pei ◽  
Bin Zhang ◽  
Huili Ma ◽  
Wanzhen Liang
Keyword(s):  
Density Functional ◽  
Energy Gap ◽  
Coupling Effect ◽  
Delayed Fluorescence ◽  
Vibronic Coupling ◽  
Time Dependent ◽  
Rate Coefficients ◽  
Quantitative Prediction ◽  
Intersystem Crossing ◽  
Triplet Energy

Assessing and improving the performance of organic light-emitting diode (OLED) materials require quantitative prediction of rate coefficients for the intersystem crossing (ISC) and reverse ISC (RISC) processes, which are determined not only by the singlet-triplet energy gap and the direct spin-orbit coupling (SOC) at a thermal equilibrium position of the initial electronic state but also by the non-Condon effects such as the Herzberg-Teller vibronic coupling (HTVC) and the spin-vibronic coupling (SVC). Here we applied the time-dependent correlation function approaches to calculate the vibronic absorption and fluorescence spectra and ISC and RISC rates of a newly synthesized multiple-resonance-type (MR-type) thermally activated delayed fluorescence (TADF) emitter, 7-phenylquinolino[3,2,1-de]acridine-5,9-dione (7-PhQAD), with inclusion of the Franck-Condon (FC), HTVC, and Duschinsky rotation effects. It is found that the experimentally-measured ISC rate of 7-PhQAD originates predominantly from the HTVC which increases the ISC rate by more than one order of magnitude while the HTVC effect on the vibronic spectra is negligible. The small discrepancy between the theoretical and experimental rates originates from the neglect of the second-order SVC and the inaccurate excited states calculated by the single-reference time-dependent density functional theory. This work provides a demonstration of what proportion of ISC and RISC rate coefficients of a MR-type TADF emitter can be covered by the contribution of HTVC, and opens design routes that go beyond the FC approximation for the future development of high-performance systems.

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