Temat: 33.50.-j - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: Emission Spectra of Triple Activated SrS Phosphors
Autorzy:: Rao, A. P.
Sinha, O. P.
Machwe, V. G.
Mehta, A. S.
Tematy:: 33.50.-j; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1945381.pdf Link otwiera się w nowym oknie
Opis:: Fluorescence spectra of strontium sulphide phosphors activated by three activators viz. Mn, Cu, and Gd individually and in different combinations have been discussed at length. X-ray is used as excitation source. Probable inferences are drawn regarding energy transfer phenomenon. The two channels for transfer of energy are concluded in present phosphor series. A model is also proposed.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Empirical L Shell Fluorescence Yields for Elements with 40 ≤ Z ≤ 92
Autorzy:: Bendjedi, A.
Deghfel, B.
Derradj, I.
Kahoul, A.
Khalfallah, F.
Sahnoune, Y.
Bentabet, A.
Nekkab, M.
Tematy:: 33.50.-j; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1030357.pdf Link otwiera się w nowym oknie
Opis:: Based on the fact that ratio of ionization to X-ray production cross-sections are independent of the excitation energy of projectile for a given target, we have deduced a new values of L shell average fluorescence yield from existing experimental compilation (till 2014) for a wide range of elements (40 ≤ Z ≤ 92) by proton impact (up to 10.0 MeV) of ionization and X-ray production cross-sections which are found to be universal when plotted as a function of the scaled velocity of projectile. The obtained empirical cross-sections are found reliable and then exploited to derive new values of average fluorescence yield. The obtained values are compared with earlier theoretical and experimental results and an agreement is observed for all elements.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Fluorescence Decay Heterogeneity Model Based on Electron Transfer Processes in an Enzyme-Ligand Complex
Autorzy:: Wlodarczyk, J.
Kierdaszuk, B.
Tematy:: 33.50.-j; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/2043367.pdf Link otwiera się w nowym oknie
Opis:: The models are described for complex fluorescence decay of tyrosine in proteins involving continuous distribution of fluorescence lifetimes and electron transfer processes. We introduce the analytical decay function with a power-like term, which provides good fits to highly complex fluorescence decays. Moreover, the power-like term in the proposed decay functions is a manifestation of so-called Tsallis nonextensive statistics and is suitable for description of the systems with long-range interactions, memory effect, as well as with fluctuations of the characteristic lifetime of fluorescence. The proposed decay functions were applied to analysis of fluorescence decays of tyrosine in a protein, i.e. the enzyme purine nucleoside phosphorylase from E. coli, free in aqueous solution and in the complex with formycin A (an inhibitor) and orthophosphate (a co-substrate), and demonstrated that both models reflect the enzyme-ligand interactions. Direct measure of heterogeneity of the enzyme systems is provided by a variance of fluorescence lifetime distribution. The possible number of deactivation channels and excited state mean lifetime can be easily derived without a priori knowledge of the complexity of studied system.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: Anisotropic Fluorescence of Polar Molecules in External Electric Field, Dipole Moments of Para-Disubstituted Transstilbenes in the First Excited Singlet State
Autorzy:: Kawski, A.
Kubicki, A.
Tematy:: 33.50.-j; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1887289.pdf Link otwiera się w nowym oknie
Opis:: The electric dipole moments μ$\text{}_{e}$ in the lowest excited singlet state of nine short-lived para-disubstituted trans-stilbenes were determined experimentally based on the effect of the external electric field on the fluorescence anisotropy. The values of μ$\text{}_{e}$ obtained from Liptay's theory with the employment of the Onsager effective field are in satisfactory agreement with those calculated based on the solvatochromic effect. In the case of para-substituted trans-stilbenes with the same donor substituent R = N(CH$\text{}_{3}$)$\text{}_{2}$ in position 4 and different acceptors R' in position 4', the enhancing electron properties of the acceptor are accompanied by the increase in μ$\text{}_{g}$ - the dipole moment in the ground state, and μ$\text{}_{e}$ - the dipole moment in the excited state. There exists a linear relation between the values of μ$\text{}_{e}$ and μ$\text{}_{g}$.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: From Jabłoński To Femtoseconds. Evolution of Molecular Photophysics
Autorzy:: Kasha, M.
Tematy:: 33.50.-j
33.50.Dq; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1993427.pdf Link otwiera się w nowym oknie
Opis:: A presentation is given, with retrospective commentary, on the experimental and theoretical contributions to key steps in the evolution of the framework of contemporary molecular photophysics from the Jablonski Diagram to femtosecond range excitation phenomena. The distinctive features of polyatomic molecules separating their behavior from atomic and diatomic molecules are emphasized. Justification is given for the statement that spin-orbital coupling with its relativistic component commonly dominates the molecular excitation dynamics of light-(low-Z)-atom molecules. The paper deals with single-photon, single-molecule excitations. Some examples of single-photon, multi-molecule and multi-photon, single-molecule excitation phenomena are listed. A selection of these is made to illustrate the prevalence of femtosecond excitation modes.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: Structural Aspects of Photochromism of the Internally H-Bonded Schiff Bases. "A Minimal Chromophore"
Autorzy:: Grabowska, A.
Kownacki, K.
Kaczmarek, Ł.
Tematy:: 33.10.-n
33.50.-j; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1943895.pdf Link otwiera się w nowym oknie
Opis:: The final limiting stage of structural simplification of photochromic Schiff base was reached by the following statement: two molecules, salicylidene methylamine and its butyl analogue, show transient absorption bands (at room temperature) peaking at ≈ 22000 cm$\text{}^{-1}$. These bands are characteristic of the phenomenon of photochromism. They are similar to the corresponding spectra detected earlier for several larger, symmetric systems belonging to the same family. Experimental characterization of both molecules was compared with the theoretical calculations: geometry optimization and transition energies, performed for enol, keto, and the photochromic form of salicylidene methylamine.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: Intramolecular Charge Transfer with N,N-Dialkyl-4-(Trifluoromethyl)anilines and 4-(Dimethylamino)benzonitrile in Polar Solvents. Investigation of the Excitation Wavelength Dependence of the Reaction Pathway
Autorzy:: Galievsky, V.
Zachariasse, K.
Tematy:: 33.20.-t
33.50.-j; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1813985.pdf Link otwiera się w nowym oknie
Opis:: In the series of N,N-di-n-alkyl-4-(trifluoromethyl)anilines (DXCF3), with X = M (methyl), E (ethyl), Pr (n-propyl) and Pe (n-pentyl), an intramolecular charge transfer (ICT) reaction takes place in the polar solvent acetonitrile (MeCN). Such a reaction does not occur in the less polar solvents $n$-hexane and diethyl ether, in which a single fluorescence band from the locally excited (LE) state is observed. For DMCF3 in MeCN at 25ºC, the intramolecular charge transfer reaction efficiency is much smaller than for 4-(dimethylamino)benzonitrile (DMABN) in this solvent, as seen from the ICT/LE fluorescence quantum yield ratio Φ'(ICT)/Φ(LE): 0.06 for DMCF3 and 39.5 for DMABN. As predicted by the planar ICT (PICT) model, this difference is caused by the considerably larger energy gap Δ E($S_1$,S_2) of DMCF3 (5750 $cm^{-1}$) as compared with that of DMABN (3130 $cm^{-1}$). When the alkyl chain length of DXCF3 becomes larger, Φ'(ICT)/Φ(LE) in MeCN at 25ºC increases, from 0.06 for DMCF3 to 0.64 for DPeCF3. This increase in ICT reaction efficiency is accompanied by a small but significant decrease of 380 $cm^{-1}$ for Δ E($S_1$,S_2) when going from DMCF3 to DPeCF3. Because of their relatively large Δ E($S_1$,S_2) gap, the molecules DXCF3 are suitable for an investigation of the excitation wavelength dependence of the intramolecular charge transfer reaction. For DPrCF3 in MeCN, the same Φ'(ICT)/Φ(LE) is found for excitation in the $S_1$ or in the $S_2$ manifold. A similar result is obtained with DMABN in tetrahydrofuran. From these experiments it is concluded that for DPrCF3 and DMABN the intramolecular charge transfer reaction follows an adiabatic pathway. After excitation to a Franck-Condon $S_n(FC)$ state, the electron donor/acceptor molecules first undergo ultrafast internal conversion to the relaxed $LE(S_1)$ state, from which precursor the reaction proceeds to the ICT state. Experimental evidence for a nonadiabatic ICT reaction pathway, going directly from $S_2(FC)$ via an $S_2//S_1$ conical intersection to the LE and ICT state, is not found. This pathway would lead to an enhancement of the ICT population, i.e., to an increase in Φ'(ICT)/Φ(LE), as compared with the adiabatic LE → ICT reaction.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: Spin-Allowed Vibronic Transitions in Molecules: Radiative and Non-Radiative Transition Moments by Including Static and Vibronic Spin-Orbit Coupling within the Adiabatic Approximation
Autorzy:: Gustav, K.
Tematy:: 33.50.-j
82.50.-m; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1891927.pdf Link otwiera się w nowym oknie
Opis:: By making use of the second order Herzberg-Teller approach within the adiabatic approximation including the static and vibronic spin-orbit coupling the vibronic transition moments for spin-allowed radiative and non-radiative processes are derived. The role and the contribution of spin-orbit coupling to both transition moments are illustrated.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: Excitation Energy Transport between the Ionic Forms of Rhodamine B in Viscous Solutions
Autorzy:: Bojarski, P.
Kułak, L.
Tematy:: 31.15.-p
33.50.-j; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1992720.pdf Link otwiera się w nowym oknie
Opis:: Excitation energy transport between zwitterion and cationic form of rhodamine B in glycerol-ethanol mixture is studied. Concentration course of the quantum yield exhibits a rapid drop at intermediate concentrations, where no dimers are formed contrary to the results of measurements carried out for solutions with a trace amount of acid or base in which single ionic forms are adopted. To describe properly such concentration behavior of the quantum yield forward and reverse, nonradiative excitation energy transport between the forms is considered. This task is performed by comparing experimental data with Monte-Carlo simulations.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: Remarks on Fluorescence Concentration Quenching of Rhodamine 6G in Methanol
Autorzy:: Bojarski, C.
Bujko, R.
Bojarski, P.
Tematy:: 33.50.-j
78.55.Bg; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1887297.pdf Link otwiera się w nowym oknie
Opis:: It has been shown that the concentration changes in the quantum yield η and decay time τ of fluorescence of rhodamine 6G in methanol can be explained quantitatively by non-radiative excitation energy transport (NET) from monomers to quenching centres considered as perfect traps. The good agreement of the experimental data with the theoretical curves for the critical radii R$\text{}_{OMM}$ = 55.4Ǻ and R$\text{}_{OMT}$ = 51.8Ǻ determined spectroscopically has been obtained. The excitation energy migration and the concentration dependence on the orientation factor occurring in the Förster rate for the NET have been taken into account. The nature of the quenching centres and the effect of material diffusion of active molecules on η and τ have been discussed.
Dostawca treści:: Biblioteka Nauki

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