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1
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Empirical L Shell Fluorescence Yields for Elements with 40 ≤ Z ≤ 92

100%
Bendjedi A., Deghfel B., Derradj I., Kahoul A., Khalfallah F., Sahnoune Y., Bentabet A., Nekkab M.
Acta Physica Polonica A
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2017
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vol. 131
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issue 1
13-15
EN
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.
2
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Fluorescence Decay Heterogeneity Model Based on Electron Transfer Processes in an Enzyme-Ligand Complex

100%
Wlodarczyk J., Kierdaszuk B.
Acta Physica Polonica A
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2005
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vol. 107
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issue 6
883-894
EN
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.
3
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Anisotropic Fluorescence of Polar Molecules in External Electric Field, Dipole Moments of Para-Disubstituted Transstilbenes in the First Excited Singlet State

100%
Kawski A., Kubicki A.
Acta Physica Polonica A
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1991
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vol. 79
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issue 4
457-470
EN
The electric dipole moments μ_{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_{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_{3})_{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_{g} - the dipole moment in the ground state, and μ_{e} - the dipole moment in the excited state. There exists a linear relation between the values of μ_{e} and μ_{g}.
4
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Emission Spectra of Triple Activated SrS Phosphors

100%
Rao A., Sinha O., Machwe V., Mehta A.
Acta Physica Polonica A
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1996
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vol. 89
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issue 4
509-516
EN
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.
5
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Spin-Allowed Vibronic Transitions in Molecules: Radiative and Non-Radiative Transition Moments by Including Static and Vibronic Spin-Orbit Coupling within the Adiabatic Approximation

63%
Gustav K.
Acta Physica Polonica A
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1991
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vol. 80
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issue 6
793-800
EN
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.
6
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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

63%
Galievsky V., Zachariasse K.
Acta Physica Polonica A
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2007
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vol. 112
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issue S
S-39-S-56
EN
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.
7
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Structural Aspects of Photochromism of the Internally H-Bonded Schiff Bases. "A Minimal Chromophore"

63%
Grabowska A., Kownacki K., Kaczmarek Ł.
Acta Physica Polonica A
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1995
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vol. 88
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issue 6
1081-1088
EN
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^{-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.
8
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From Jabłoński To Femtoseconds. Evolution of Molecular Photophysics

63%
Kasha M.
Acta Physica Polonica A
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1999
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vol. 95
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issue 1
15-36
EN
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.
9
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Remarks on Fluorescence Concentration Quenching of Rhodamine 6G in Methanol

63%
Bojarski C., Bujko R., Bojarski P.
Acta Physica Polonica A
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1991
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vol. 79
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issue 4
471-478
EN
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_{OMM} = 55.4Ǻ and R_{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.
10
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The Geometry of the Excited Charge Transfer States: Flattening or Twisting?

63%
Dobkowski J., Sazanovich I.
Acta Physica Polonica A
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2007
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vol. 112
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issue S
S-127-S-142
EN
Numerous molecules built of an electron acceptor and electron donor units linked together by single bond exhibit a peculiar behavior in their low-lying electronically excited states. N,N-diethylaminoacetophenone and 4-acetyl-4'-dimethylamino-biphenyl, having acetophenone as the acceptor and differentiated by the donors groups N(CH_3)_2 and dimethylaniline, respectively, were selected as the subject of study. To recognize the excited state relaxation paths the stationary and time-resolved spectroscopy in absorption and emission was applied. Experimental results indicate that after excitation in polar solvents N,N-diethylaminoacetophenone reduces to minimum the overlap between π-electron systems of the donor and acceptor groups relaxing to the twisted internal charge-transfer state; contrary to that, flattening of the 4-acetyl-4'-dimethylamino-biphenyl skeleton generates increase in the overlap of the π-electron systems.
11
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Excitation Energy Transport between the Ionic Forms of Rhodamine B in Viscous Solutions

63%
Bojarski P., Kułak L.
Acta Physica Polonica A
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1998
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vol. 94
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issue 5-6
725-734
EN
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.
12
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Spin-Allowed Vibronic Transitions in Molecules: a Refined Treatment of Vibrationally-Structured Electronic Spectra and of Internal Conversion within the Adiabatic Approximation

63%
Gustav K.
Acta Physica Polonica A
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1991
|
vol. 80
|
issue 4
521-526
EN
By making use of second-order Herzberg-Teller approach within the adiabatic approximation the vibronic transition moments are derived for intramolecular spin-allowed radiative and non-radiative processes. The differences to the hitherto existing method are presented and discussed.
13
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Emission of Acridine and its Aggregates Isolated in the Neon Matrix

63%
Prochorow J., Kozankiewicz B., Dongo Gemi B. B., Morawski O.
Acta Physica Polonica A
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1998
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vol. 94
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issue 5-6
749-760
EN
The results of experimental studies of fluorescence and phosphorescence of acridine in the low-temperature inert neon matrix, at 7 K, are reported. It is found that the low-temperature inert matrix of neon affects the energy levels of acridine molecules very weakly even as compared with nonpolar (aprotic) and non-reactive solvent (e.g. hexane) and that there are different sites for acridine molecules in the neon matrix. However, the observed fluorescence spectra are strongly dependent on the excitation wavelength and besides the different (monomer) sites other emitting species are also contributing to the observed fluorescence emission of acridine in the neon matrix. Clear-cut evidence of the formation of singlet excimers of acridine in the neon matrix demonstrates itself as a very broad and structureless fluorescence spectrum with a relatively large shift from the origin of monomer (site) fluorescence which is characterized by a very distinct vibrational structure. The phosphorescence emission was observed only for the monomers. The observed differences in the low-energy part of excitation spectra of phosphorescence and fluorescence are discussed in terms of the close-lying excited singlet states of n,π* and π,π* character (mixed by the vibronic coupling) and tentatively interpreted as due to the formation of resonance acridine dimers. Their fluorescence spectrum is slightly shifted toward lower energies from the origin of monomer (site) fluorescence.
14
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Energy Transfer in Peridinin-Chlorophyll-Protein-Metallic Nanoparticle Hybrid Nanostructure: Effect of Spatial Arrangement

51%
Schmidt M., Mackowski S.
Acta Physica Polonica A
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2012
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vol. 122
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issue 2
307-311
EN
We theoretically investigate dynamics of excitation in a hybrid nanostructure comprising a photosynthetic complex peridinin-chlorophyll-protein (PCP) coupled to a gold spherical nanoparticle. Our model includes the analytical description of radiative and non-radiative relaxation channels of the chlorophylls in PCP, as well as the change of energy transfer rate within the PCP due to the presence of metal scatterer. We show that by measuring the intensity of fluorescence from selectively excited chlorophyll molecules in the PCP complex, elementary geometric properties of the system can be deduced.
15
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Enhancement of FITC Fluorescence by Silver Colloids and Silver Island Films

51%
Kruszewski S., Wybranowski T., Cyrankiewicz M., Ziomkowska B., Pawlaczyk A.
Acta Physica Polonica A
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2008
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vol. 113
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issue 6
1599-1608
EN
Silver colloids and silver island films as fluorescence enhancement systems are the subject of this paper. Enhancement of fluorescence of molecules placed near metallic nanoparticles is a result of resonance interaction of exciting and emitted lights with surface plasmons. Two models explaining this phenomenon are presented. Processes of silver colloids and silver island films forming are described. Results of extinction, absorption and scattering studies of fluorescence enhancement systems are presented. The influence of these systems, i.e. silver colloids and silver island films on the fluorescence of fluorescein-5-isothiocyanate was studied. 7-fold increase in fluorescence intensity of fluorescein-5-isothiocyanate molecules placed near silver nanoparticles was observed.
16
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Light-Induced Tautomerization in Porphyrin Isomers

51%
Waluk J.
Acta Physica Polonica A
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1999
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vol. 95
|
issue 1
49-62
EN
Double proton tautomerization occurring in porphyrin and its structural isomers represents a special case of a chemical transformation in which the substrate and the product are form ally the same. The methods used for the investigation of this kind of processes are based on polarized spectroscopy and high-resolution techniques, such as matrix isolation. Their combined use results in obtaining information pertinent to the mechanism of proton transfer, regarding e.g., the values of proton transfer rates, structure of the tautomeric forms or the shape of the potential energy surfaces. In addition, these procedures provide a way of obtaining spectral, photophysical and structural data that would be otherwise difficult to gain. The examples include determination of transition moment directions, assignment of electronic and vibrational states, elucidation of the character of the substitutional replacement of the rare gas matrix atoms by the chromophore, and the analysis of the nature of the symmetry lowering due to the matrix cage.
17
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Aggregated Silver Sols as SERS Substrates

51%
Kruszewski S., Cyrankiewicz M.
Acta Physica Polonica A
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2012
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vol. 121
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issue 1A
A-68-A-74
EN
The unique plasmonic properties of the noble metal colloidal nanoparticles make them promising enhancement substrates for surface-enhanced Raman scattering. Obtaining of systems that provide ever-increasing enhancement of the Raman scattered light is a big challenge. Silver colloids studied here are prepared by Lee-Meisel's method. Rhodamine 6G and rhodamine B are used as probe adsorbates. The "raw" colloids obtained in this way exhibit a characteristic extinction band proving surface plasmons excitation, but do not enhance the Raman signal. Theoretical calculations indicate that the extremely large electromagnetic field is induced in the junctions between metallic nanostructures so some degree of their aggregation is necessary to achieve a sufficient gain value. The addition of aggregating agents (KCl or HCl) leads to significant changes in the extinction spectrum and to significant increase in the intensity of surface-enhanced Raman scattering. The experiments show that chloride can not only promote the aggregation process but also effectively affect chemical mechanisms contributing to surface-enhanced Raman scattering.
18
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Influence of Silver Colloid on Fluorescein Spectral Properties

51%
Frąckowiak D., Balter A., Karolczak J., Siejak P.
Acta Physica Polonica A
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2006
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vol. 110
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issue 4
451-458
EN
In order to check if the observed earlier changes in fluorescence intensities of fluorescein solution due to the addition of colloidal suspension of silver are related to the generation of surface plasmon coupled emission, the steady state photothermal spectra and fluorescence decay times of such samples were measured. The Gaussian components of photoacoustic spectra for solutions with and without silver colloid addition were determined and compared with components of absorption and fluorescence excitation spectra of the same samples. The efficiencies of thermal and radiative deactivation of various samples were discussed. The fluorescence decay times measured at the wavelength of excitation not exhibiting the increase in photonic mode density depend only on the dye concentration. Decays exhibit changes as a result of silver addition with excitation in the region in which enhancement of fluorescence is observed. These changes are due not only to the change in the fluorescence yield generated by interactions with plasmons but also to those in thermal deactivation of the sample related to the colloid presence.
19
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Optical Biopsy Method for Breast Cancer Diagnosis Based on Artificial Neural Network Classification οf Fluorescence Landscape Data

51%
Dramićanin T., Zeković I., Dimitrijević B., Ribar S., Dramićanin M.
Acta Physica Polonica A
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2009
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vol. 116
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issue 4
690-692
EN
Supervised self-organizing map, a type of artificial neural network, is applied for classification of human breast tissue samples utilizing data obtained from fluorescence landscape measurements. Female breast tissue samples were taken soon after the surgical resection, identified and stored at -80°C until fluorescence measurements. From fluorescence landscapes obtained in UV-VIS region spectral features showing statistically significant differences between malignant and normal samples are identified and further quantified to serve as a training input to neural network. Additional set of samples was used as a test group input to trained network in order to evaluate performance of proposed optical biopsy method. Classification sensitivity of 83.9% and specificity of 88.9% are found.
20
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Picosecond Transient Absorption of Xanthene Dyes

51%
Berndt O., Bandt F., Eichwurzel I., Stiel H.
Acta Physica Polonica A
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1999
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vol. 95
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issue 2
207-220
EN
After one- and two-colour ps-excitation the transient absorption of rose bengal, erythrosin B and eosin Y in the spectral range from 450 to 670 nm was probed using picosecond continuum pulses generated in H_{2}O-D_{2}O mixture. Our experiments showed for all dyes a high T_{1}-T_{n} absorption signal above 590 nm where no ground state absorption occurs. These excited triplet states can be effectively populated by a delayed second pump pulse. Their properties with special attention to reverse intersystem crossing processes from T_{n} to S_{x} are discussed.
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