Search results for "ELECTRONIC STRUCTURE"
showing 10 items of 722 documents
Photoluminescence in ZnO:Co2+ (0.01%–5%) Nanoparticles, Nanowires, Thin Films, and Single Crystals as a Function of Pressure and Temperature: Explori…
2014
This work investigates the electronic structure and photoluminescence properties of Co2+-doped ZnO and their pressure and temperature dependences through high-resolution absorption and emission spe...
Luminescence activity of surface and interior Ge-oxygen deficient centers in silica
2005
We report a comparative study on the optical activity of surface and interior Ge–oxygen deficient centers in pressed porous and sol–gel Ge-doped silica, respectively. The experimental approach is based on the temperature dependence of the two photoluminescence bands at 4.2 (singlet–singlet emission, S1! S0) and 3.1 eV (triplet–singlet emission, T1! S0), excited within the absorption band at about 5 eV. Our data show that the phonon assisted intersystem crossing process, linking the two excited electronic states, more effective for surface than for interior centers in the temperature range 5–300 K. For both centers, a distribution of the activation energies of the process is found. Based on th…
Computational evidence in favor of a two-state, two-mode model of the retinal chromophore photoisomerization
2000
In this paper we use ab initio multiconfigurational second-order perturbation theory to establish the intrinsic photoisomerization path model of retinal chromophores. This is accomplished by computing the ground state ( S 0 ) and the first two singlet excited-state ( S 1 , S 2 ) energies along the rigorously determined photoisomerization coordinate of the rhodopsin chromophore model 4- cis -γ-methylnona-2,4,6,8-tetraeniminium cation and the bacteriorhodopsin chromophore model all- trans -hepta-2,4,6-trieniminium cation in isolated conditions. The computed S 2 and S 1 energy profiles do not show any avoided crossing feature along the S 1 reaction path and maintain an energy gap >20 kcal⋅…
First-Principles Computed Rate Constant for the O + O 2 Isotopic Exchange Reaction Now Matches Experiment
2018
We show, by performing exact time-independent quantum molecular scattering calculations, that the quality of the ground electronic state global potential energy surface appears to be of utmost importance in accurately obtaining even as strongly averaged quantities as kinetic rate constants. The oxygen isotope exchange reaction, 18O + 32O2, motivated by the understanding of a complex long-standing problem of isotopic ozone anomalies in the stratosphere and laboratory experiments, is explored in this context. The thermal rate constant for this key reaction is now in quantitative agreement with all experimental data available to date. A significant recent progress at the frontier of three rese…
Energy and radiative properties of the (3)Π1 and (5)Σ+1 states of RbCs: Experiment and theory
2017
We combined high-resolution Fourier-transform spectroscopy and large-scale electronic structure calculation to study energy and radiative properties of the high-lying $(3)^{1}\mathrm{\ensuremath{\Pi}}$ and $(5)^{1}\mathrm{\ensuremath{\Sigma}}^{+}$ states of the RbCs molecule. The laser-induced $(5)^{1}\mathrm{\ensuremath{\Sigma}}^{+},(4)^{1}\mathrm{\ensuremath{\Sigma}}^{+},(3)^{1}\mathrm{\ensuremath{\Pi}}\ensuremath{\rightarrow}A(2)^{1}\mathrm{\ensuremath{\Sigma}}^{+}\ensuremath{\sim} b(1)^{3}\mathrm{\ensuremath{\Pi}}$ fluorescence (LIF) spectra were recorded by the Bruker IFS-125(HR) spectrometer in the frequency range $\ensuremath{\nu}\ensuremath{\in}[5500,10\phantom{\rule{0.16em}{0ex}}00…
Electronic structure of Rf+ (Z=104) from ab initio calculations
2021
We report calculation of the energy spectrum and the spectroscopic properties of the superheavy element ion: ${\mathrm{Rf}}^{+}$. We use the four-component relativistic Dirac-Coulomb Hamiltonian and the multireference configuration interaction model to tackle the complex electronic structure problem that combines strong relativistic effects and electron correlation. We determine the energies of the ground and the low-lying excited states of ${\mathrm{Rf}}^{+}$, which originate from the $7{s}^{2}6{d}^{1},\phantom{\rule{0.28em}{0ex}}7{s}^{1}6{d}^{2},\phantom{\rule{0.28em}{0ex}}7{s}^{2}7{p}^{1}$, and $7{s}^{1}6{d}^{1}7{p}^{1}$ configurations. The results are discussed vis-\`a-vis the lighter h…
Fourier-transform spectroscopy, direct potential fit, and electronic structure calculations on the entirely perturbed (4) 1Π state of RbCs
2018
We perform a high-resolution Fourier-transform spectroscopic study of the $(4){\phantom{\rule{0.16em}{0ex}}}^{1}\mathrm{\ensuremath{\Pi}}$ state of the RbCs molecule by applying two-step $(4){\phantom{\rule{0.16em}{0ex}}}^{1}\mathrm{\ensuremath{\Pi}}\ensuremath{\leftarrow}A{\phantom{\rule{0.16em}{0ex}}}^{1}{\mathrm{\ensuremath{\Sigma}}}^{+}\ensuremath{\sim}b{\phantom{\rule{0.16em}{0ex}}}^{3}\mathrm{\ensuremath{\Pi}}\ensuremath{\leftarrow}X{\phantom{\rule{0.16em}{0ex}}}^{1}{\mathrm{\ensuremath{\Sigma}}}^{+}$ optical excitation followed by observation of the $(4){\phantom{\rule{0.16em}{0ex}}}^{1}\mathrm{\ensuremath{\Pi}}\ensuremath{\rightarrow}X{\phantom{\rule{0.16em}{0ex}}}^{1}{\mathrm{\ensu…
Fourier-transform spectroscopy, relativistic electronic structure calculation, and coupled-channel deperturbation analysis of the fully mixed A1Σu+ a…
2019
The 4503 rovibronic term values belonging to the mutually perturbed $A^1\Sigma^+_u$ and $b^3\Pi_u$ states of Cs$_2$ were extracted from laser induced fluorescence (LIF) $A\sim b\rightarrow X^1\Sigma^+_g$ Fourier transform spectra with the 0.01 cm$^{-1}$ uncertainty. The experimental term values of the $A^1\Sigma^+_u\sim b^3\Pi_u$ complex covering the rotational levels $J\in [4,395]$ in the excitation energy range $[9655,13630]$ cm$^{-1}$ were involved into coupled-channel (CC) deperturbation analysis. The deperturbation model takes explicitly into account spin-orbit coupling of the $A^1\Sigma^+_u(A0^+_u)$ and $b^3\Pi^+_{0_u}(b0^+_u)$ states as well as spin-rotational interaction between the…
Ab-Initio Studies of Electronic and Spectroscopic Properties of MgO, ZnO and CdO
2008
We present ab-initio calculations of excited-state properties within single-particle and two-particle approaches in comparison with corresponding experimental results. For the theoretical treatment of the electronic structure, we compute eigenvalues and eigenfunctions by using a spatially nonlocal exchange-correlation potential. From this starting point, quasiparticle energies within the fully frequency-dependent G(0)W(0) approximation are obtained. By solving the Bethe-Salpeter equation, we evaluate optical properties, including the electron-hole attraction and the local-field effects. The results are compared with experimental spectra from soft X-ray emission, as well as from X-ray photoe…
Spatial multifractal properties of wave packets in the Anderson model of localization.
1993
The multifractal properties of electronic wave functions in disordered samples are investigated. In a given energy range all eigenstates are determined for the same disorder configuration in the Anderson model of localization. It is shown that the singularity spectrum and the generalized dimensions change only slowly with energy, aside from statistical fluctuations. More important, the wave packet constructed by linear combination of the eigenstates shows quantitatively the same multifractal properties. Consequences for the transport properties of electronic states in disordered systems are discussed.