transition energies
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2021 ◽  
Vol 122 ◽  
pp. 111656
Author(s):  
Mega Novita ◽  
Irna Farikhah ◽  
Dian Marlina ◽  
Chong-Geng Ma ◽  
Benjamin Walker ◽  
...  

2021 ◽  
Vol 38 (11) ◽  
pp. 113101
Author(s):  
Qing Liu ◽  
Jiguang Li ◽  
Jianguo Wang ◽  
Yizhi Qu

The transition energies, E1 transitional oscillator strengths of the spin-allowed as well as the spin-forbidden and the corresponding transition rates, and complete M1, E2, M2 forbidden transition rates for 1s 2, 1s2s, and 1s2p states of He I, are investigated using the multi-configuration Dirac–Hartree–Fock method. In the subsequent relativistic configuration interaction computations, the Breit interaction and the QED effect are considered as perturbation, separately. Our transition energies, oscillator strengths, and transition rates are in good agreement with the experimental and other theoretical results. As a result, the QED effect is not important for helium atoms, however, the effect of the Breit interaction plays a significant role in the transition energies, the oscillator strengths and transition rates.


Molecules ◽  
2021 ◽  
Vol 26 (23) ◽  
pp. 7163
Author(s):  
Karolina Filipowska ◽  
Marek T. Pawlikowski ◽  
Marcin Andrzejak

There is experimental evidence of high vibronic activity that accompanies the allowed transition between the ground state and the lowest electronic singlet excited state of oligofurans that contain two, three, and four furan rings. The absorption and emission spectra of the three lowest oligofurans measured at liquid nitrogen temperature show distinct fine structures that are reproduced using the projection-based model of vibronic coupling (with Dushinsky rotation included) parameterized utilizing either Density Functional Theory (DFT, with several different exchange-correlation functionals) or ab initio (CC2) quantum chemistry calculations. Using as a reference the experimental data concerning the electronic absorption and fluorescence for the eight lowest oligofurans, we first analyzed the performance of the exchange-correlation functionals for the electronic transition energies and the reorganization energies. Subsequently, we used the best functionals alongside with the CC2 method to explore how the reorganization energies are distributed among the totally symmetric vibrations, identify the normal modes that dominate in the fine structures present in the absorption and emission bands, and trace their evolution with the increasing number of rings in the oligofuran series. Confrontation of the simulated spectra with the experiment allows for the verification of the performance of the selected DFT functionals and the CC2 method.


Atoms ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 101
Author(s):  
Timur A. Isaev ◽  
Shane G. Wilkins ◽  
Michail Athanasakis-Kaklamanakis

Polar radioactive molecules have been suggested to be exceptionally sensitive systems in the search for signatures of symmetry-violating effects in their structure. Radium monofluoride (RaF) possesses an especially attractive electronic structure for such searches, as the diagonality of its Franck-Condon matrix enables the implementation of direct laser cooling for precision experiments. To maximize the sensitivity of experiments with short-lived RaF isotopologues, the molecular beam needs to be cooled to the rovibrational ground state. Due to the high kinetic energies and internal temperature of extracted beams at radioactive ion beam (RIB) facilities, in-flight rovibrational cooling would be restricted by a limited interaction timescale. Instead, cooling techniques implemented on ions trapped within a radiofrequency quadrupole cooler-buncher can be highly efficient due to the much longer interaction times (up to seconds). In this work, the feasibility of rovibrationally cooling trapped RaF+ and RaH+ cations with repeated laser excitation is investigated. Due to the highly diagonal nature between the ionic ground state and states in the neutral system, any reduction of the internal temperature of the molecular ions would largely persist through charge-exchange without requiring the use of cryogenic buffer gas cooling. Quasirelativistic X2C and scalar-relativistic ECP calculations were performed to calculate the transition energies to excited electronic states and to study the nature of chemical bonding for both RaF+ and RaH+. The results indicate that optical manipulation of the rovibrational distribution of trapped RaF+ and RaH+ is unfeasible due to the high electronic transition energies, which lie beyond the capabilities of modern laser technology. However, more detailed calculations of the structure of RaH+ might reveal possible laser-cooling pathways.


Author(s):  
Karolina Filipowska ◽  
Marek T. Pawlikowski ◽  
Marcin Andrzejak

There is experimental evidence of high vibronic activity that accompanies the strongly allowed transition between the ground state and the lowest electronic singlet excited state of oligofurans that contain 2,3, and 4 furan rings. The absorption and emission spectra of the three lowest oligofurans measured in liquid nitrogen temperature show distinct fine structures that are reproduced using the projection-based model of vibronic coupling (with Dushinsky rotation included) parameterized utilizing either DFT (with several different exchange-correlation functionals) or ab initio (CC2) quantum chemistry calculations. Using as reference the experimental data concerning the electronic absorption and fluorescence for the 8 lowest oligofurans we first analyze the performance of the exchange-correlation functionals for the electronic transition energies and the reorganization energies. Subsequently, we use the best functionals alongside the CC2 method to explore how the reorganization energies are distributed among the totally symmetric vibrations, identify the normal modes that dominate in the fine structures present in the absorption and emission bands, and trace their evolution with the increasing number of rings in the oligofuran series. Confrontation of the simulated spectra with the experiment allows for verification of the performance of the selected DFT functionals and the CC2 method.


2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Mohamed Omri ◽  
Amor Sayari ◽  
Larbi Sfaxi

In this work, a theoretical study of the electronic and the optical properties of a new family of strain-free GaAs/AlGaAs quantum dots (QDs) obtained by AlGaAs nanohole filling is presented. The considered model consists of solving the three-dimensional effective-mass Schrödinger equation, thus providing a complete description of the neutral and charged complex excitons’ fine structure. The QD size effect on carrier confinement energies, wave functions, and s-p splitting is studied. The direct Coulomb interaction impact on the calculated s and p states’ transition energies is investigated. The behaviour of the binding energy of neutral and charged excitons (X− and X+) and biexciton XX versus QD height is studied. The addition of the correlation effect allows to explain the nature of biexcitons often observed experimentally.


2021 ◽  
Vol 1039 ◽  
pp. 373-381
Author(s):  
Taif Saad Al Maadhde ◽  
Mohammad Hafizuddin Jumali ◽  
Hadi J.M. Al-Agealy ◽  
Fatimah Binti Abdul Razak ◽  
Chi Chin Yap

This study investigated and calculated the fill factor and efficiency of N719 and D149 organic dyes in titanium dioxide (TiO2) solar cell systems using a current equation that we derived using a quantum transition-state theory (TST). The theory of charge transfer reactions was used to investigate the electronic current to enhance both the fill factor and efficiency of both N719/ and D149/TiO2 solar cell systems. The current calculated for Di-terabtylammoniumcis-bis (isthiocyanato) bis (2,2-bipyridyl-4,4dicarboxylato) ruthenicyanatoum (II)(N719) and 5-[[4-[4-(2,2-Diphenylethenyl) phenyl]-1,2,3-3a,4,8b-hexahydrocyclopent [b] indol-7-yl] methylene]-2-(3-ethyl-4-oxo-2-thioxo-5-thiazolidinylidene)-4-oxo-3-thiazolidineacetic acid indicated that the molecules of D149, an indoline-based dye, have to be in contact with the semiconductor due to the quantum donor-acceptor scenario model. The efficiency of N719/and D149/TiO2 solar cells were significantly affected due to transition energy, which is caused by the mechanisms of the charge transfer process. Solvents; such as trifluoroethanol (C2H3F3O), propanol (C3H8O), ethanol (C2H5OH), and acetonitrile (C2H3N); were used to determine the current, fill factor, and efficiency. Coefficients of charge transfer; such as transition energy, barrier, driving force energy, current, power-conversion efficiency, fill factor (FF), and efficiency; were evaluated theoretically. The current of the N719/ system with acetonitrile and ethanol solvents was higher than current of the N719/ system with trifluoroethanol and propanol solvents. While the current of the D149/ system with trifluoroethanol and propanol solvents was higher than current of the D149/ system with acetonitrile and ethanol solvents. The current and transition energy efficiencies of both systems varied. devices were found to have the best power conversion efficiency and low transition energies while the power conversion efficiency was large for devices with sizeable current density and activity with lower transition energies. Keywords: Fill Factor, Efficiency, Molecule/Semiconductor, Solar Cells.


2021 ◽  
Vol 119 (2) ◽  
pp. 022101
Author(s):  
Ji Hyun Kim ◽  
Pegah Bagheri ◽  
Shun Washiyama ◽  
Andrew Klump ◽  
Ronny Kirste ◽  
...  

2021 ◽  
Vol 42 (1) ◽  
pp. 97
Author(s):  
Silvio José Prado

In this work we theoretically study how to optimize the efficiency of an intermediate band solar cell based on IV-VI PbTe/CdTe semiconductor materials. We focus our attention on how control structural parameters, such as the height and radius in cylindrical quantum dots and the radius in spherical quantum dots to obtain the inter and intraband transition energies that provide the highest efficiency values of the solar cell. The calculation of the energy levels, the selection rules for transitions energies were performed using the 4×4 k.p Kane-Dimmok Hamiltonian.


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