Probing of the spectral diffusion in doped glasses by fluctuations of dichroism

A method of studying spectral diffusion using temporal fluctuations of the dichroism of an isotropic sample is described. Unlike conventional methods of absorption spectroscopy of single molecules, this method is easier to realize, provides direct information about the distribution of two-level systems over the relaxation rate, and does not require that the absorption lines be Stark modulated in frequency. The latter fact means that this method is applicable to conducting matrices (e.g., for studying current-induced relaxations in polymer materials). In combination with the probing of spectral diffusion using fluorescence intensity fluctuations, this method allows one to determine the degree of correlation between the distributions of impurity centers over the relaxation rate and over the fluorescence quantum yield.     

Photoselection of impurity centers in amorphous media over the hole-burning rate and the value of the induced Stark moment

It is shown that probing of the bottom of a multi-well spectral hole by frequency-modulated light allows one to study, in amorphous systems, the subensembles of impurity molecules, whose distribution over the hole-burning quantum yield and the matrix-induced Stark moment is different (narrower) from their initial distribution. This permits the study of correlation relations between these two distributions and between each of these distributions and other distributions.     

Luminescence and migration of electron-excitation energy in diphenyl crystals

The absorption spectra and luminescence of solutions and crystals of diphenyl are studied. According to the dependence of quantum yields of fluorescence on impurity concentration, the probabilities of capture of exitons by molecules of different impurities as well as the diffusion-displacement length of singlet exitons in diphenyl crystals are determined. It is established that the probabilities of capture of exitons by the impurity depend on the overlap integral of the impurity's absorption spectra with the fluorescence spectrum of the crystalline matrix, as well as on the dimensions and configuration of the impurity molecules.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 15, No. 6, pp. 69–73, June, 1972.     

Fluorescence and phosphorescence properties of 2-cyano-6-methoxy and 2-cyano-7-methoxy naphthalene

Fluorescence and phosphorescence properties of 2-cyano-6-methoxy and 2-cyano-7-methoxy naphthalenes have been studied. It is observed that the experimentally measured fluorescence lifetimes of the two compounds are much smaller than, while their phosphorescence lifetimes are almost the same as, those of the parent naphthalene molecule. From the measured values of fluorescence quantum yield and fluorescence lifetime the intersystem crossing rate constants for the two molecules have been calculated. They are found to be ten times larger than that of naphthalene. On the other hand, the non-radiative triplet state decay rate constant in each of the two molecules is of the same magnitude as in the parent molecule.     

Determination of the distribution function of Stark dipole moments induced by a matrix in amorphous impurity systems

The burning kinetics of closely spaced equidistant holes in impurity absorption spectra of glasses and polymers is theoretically studied in an alternating electric field (alternating in the magnitude, sign, and direction). The height of barriers between wells of the burnt multiwell spectral hole depends on the shape of the distribution of impurity molecules over the Stark dipole moments. Centrally symmetric impurity molecules are considered whose Stark moment is determined exclusively by the interaction with matrix molecules. Model calculations performed for different hypothetical distribution functions of Stark moments yield substantially different kinetics. Therefore, the method described allows one to verify experimentally various hypotheses about the nature of matrix-induced Stark moments.     

A dark-field method for measuring absorption cross sections of single molecules

A method for measuring absorption cross sections of single molecules by the intensity of resonance Rayleigh light scattering using a dark-field confocal microscope is proposed. It is shown by using a conjugated polymer as an example that this method can be used to study multichromophore molecules at room temperature. The method proposed makes it possible to apply single-molecule spectroscopy to weakly fluorescing molecules, investigate the distribution of molecules over the fluorescence quantum yield and the mechanisms of photodestruction, and to obtain data on the nature of intermittent fluorescence of multichromophore objects.     

Interaction of triplet excitons with excited naphthalene and deuteronaphthalene molecules in benzophenone crystals

An increase in the intensity of the exciting light is shown to cause a significant decrease in the quantum yield and rise time of the sensitized phosphorescence of impurity C₁₀H₈ and C₁₀D₈ in benzophenone crystals. Nonlinear quenching of the impurity phosphorescence occurs because one or two excitations are quenched in the interaction of triplet excitons with impurity molecules in the excited state in which they are left after the first exciton capture. Experiments show the nature of the changes in the quantum yield and the rise time of the impurity phosphorescence as the exciting-light intensity is varied from 3.6 · 10¹² to 6 · 10¹⁶ photons/cm² · sec depends strongly on the impurity concentration, the crystal thickness, and the lifetime of the triplet state of the impurity molecules. The experimental results are in good agreement with a proposed theory for the kinetics of the interaction of triplet excitons with impurity molecules in the ground and triplet states.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 8, pp. 12–16, August, 1969.     

Optical fractionation of an ensemble of impurity molecules over the magnitude of a Stark moment induced by an amorphous matrix

A method of selective (with respect to the Stark effect) burning of a spectral hole in the 0-0 absorption band of zero-dipole impurity molecules is suggested. It is shown that in combination with the Stark modulation of the optical density of a sample, this method makes it possible to determine that contribution to the total absorption and luminescence of the sample that the impurity molecules with a preset magnitude of the matrix-induced Stark moment (provided this magnitude exceeds the mean value for the entire ensemble) make. This allows one to experimentally study both the distribution of impurity molecules over the magnitude of the Stark moment and the correlation of the Stark moment with other parameters of impurity molecules.     

Enhancement of the fluorescence of triphenylmethane dyes caused by their interaction with nanoparticles from β-diketonate complexes

We have studied the absorption and fluorescence spectra of Malachite Green and Crystal Violet in aqueous and alcoholic-aqueous solutions in which nanoparticles from Ln(III) and Sc(III) diketonates are formed at concentrations of complexes in a solution of 5–30 μM. We have shown that, if the concentrations of the dyes in the solution are lower than 0.5 μM, dye molecules are incorporated completely into nanoparticles or are precipitated onto their surface. The fluorescence intensity of these incorporated and adsorbed Malachite Green and Crystal Violet molecules increases by several orders of magnitude compared to the solution, which takes place because of a sharp increase in the fluorescence quantum yields of these dyes and at the expense of the sensitization of their fluorescence upon energy transfer from β-diketonate complexes entering into the composition of nanoparticles. We have shown that, if there is no concentration quenching, the values of the fluorescence quantum yield of the Crystal Violet dye incorporated into nanoparticles and adsorbed on their surface vary from 0.06 to 0.13, i.e., are close to the fluorescence quantum yield of this dye in solid solutions of sucrose acetate at room temperature. The independence of the fluorescence quantum yield of Crystal Violet on the morphology of nanoparticles testifies to a high binding constant of complexes and the dye. The considerable fluorescence quantum yields of triphenylmethane dyes in nanoparticles and sensitization of their fluorescence by nanoparticle-forming complexes make it possible to determine the concentration of these dyes in aqueous solutions by the luminescent method in the range of up to 1 nM.     

Special Features of Quenching of Fluorescence in the 1-Naphthol and Coumarin 1 Molecules in Binary Mixtures

The work studies the effect of intermolecular interactions on the relation between the rate constants of radiative processes and internal intercombination conversion in particlular molecule - solvent systems. The 1-naphthol complexes in binary mixtures with hydrogen bonding and those of coumarin 1 with nitrogen-nitrogen bonding are examined. The Stern - Volmer curves for the complexes with additions of nitromethane are shown to deviate from linearity.The interaction of coumarin 1 and 1-naphthol with nitromethane was simulated by the INDO/SP method to show that the lower singlet state is associated with nitromethane. The experimentally observed fluorescence band of the coumarin 1 and 1-naphthol molecules belongs to the third singlet state. The quantum yield of fluorescence from the S₃ state is decreased by an order of magnitude for the complexes under study. The quantum yield from the lower singlet state in the 1-naphthol - nitromethane complex is decreased by an order of magnitude, while in the coumarin 1 - nitromethane complex - by two orders. It is found that there is a possibility of photoprotonation in the S₁ and S₂ states for the 1-naphthol molecule along with the foregoing processes of quenching of fluorescence.__________Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 17–23, January, 2005.     

Measurement of Fluorescence Quantum Yield of Ultraviolet-Absorbing Substance Extracted from Red Alga: Porphyra yezoensis and its Photothermal Spectroscopy

Optical properties of an ultraviolet-absorbing substance (UVAS) extracted from the marine red alga, Porphyra yezoensis, have been investigated. The substance is excited by UV light, and the emitted fluorescence is detected using an intelligent fluorescence detector. The fluorescence of UVAS is weaker by four orders of magnitude than the fluorescence intensity emitted by anthracene in the same optical system. The absorbed energy is apparently not transferred to the photosynthesis process and is believed to be consumed as heat. Using photothermal spectroscopy, a signal is observed indicating that the absorbed photon energy has transferred to the heat. The waveform of the photothermal signal of UVAS is similar to that of quinoxaline, whose fluorescence quantum yield is known to be zero. It is determined that the fluorescence quantum yield and the energy of the triplet state of UVAS are 1.7 ± 0.7 ± 10⁻⁴ and 21000 ± 1000 cm ⁻¹, respectively. The conclusion is that the excited molecules of UVAS decay by passing through the triplet state and dissipate all absorbed energy as heat.     

Fluorescence Quantum Yield Determination of Propylparaben Using Flow Injection Spectroscopy

The determination of the fluorescence quantum yield of Propylparaben is introduced and applied to L-tyrosine as a standard by a new approach that can be applied to the pharmaceutical compound utilised in this study. The quantum yield is a critical figure of quality for the optical nature of a fluorophore. Numerous investigations have considered the glitter in both pharmaceutical and nature compounds for its medical and industrial significance. A straightforward method is detailed here to decide the quantum yield of Propylparaben in solution as an element of the fluorescence concentration. For this reason, L-Tyrosine is chosen as a fluorescence standard perspective to gauge the Propylparaben fluorescence quantum yield. The impacts of pH, solvents and flow rate on the assessment of quantum yield and quantum efficiency, for the reference and the solutions of Propylparaben, have been investigated. The results indicated that these parameters significantly influence the accuracy of the method. Diverse methods are concentrated on to represent distinctive quantum yield advancements with the quantum efficiency. The impact of these parameters was likewise considered. In this study, the application of the single method may be taken into consideration to compute quantum yield of Propylparaben, which was 0.36, and this is an exceptionally basic and general technique to solve the imperative issue of luminescence quantum yield assurance of other fluorescence compounds.     

若丹明6G溶液体系的荧光量子效率

本文对八种若丹明6G溶液的荧光量子效率进行了测量,并着重讨论了染料若丹明6G溶液体系的量子效率的溶剂效应.在研究中发现:若丹明6G溶渡的荧光量子效率与溶液极性(ε-1)/(2ε+1)之间存在线性关系,体系的荧光量子效率随溶剂极性的增加而下降.由于染料分子与成氢键溶剂作用愈强,能量散逸愈快将是导致这一结果的主要原因.这一规律也适用于ANS染料溶液体系中.     

Open-channel fluorescence imaging of atoms in high-gradient magnetic fields

A method of imaging distributions of cold atoms under the presence of large trapping-field-induced level shifts is investigated. By utilizing a probe laser tuned to an open transition, the fluorescence yield per atom is largely fixed throughout the trap volume, independent of the trapping field. This enables a reliable conversion of fluorescence images into atomic-density profiles. The method is applied to measure distributions of ⁸⁷Rb atoms in a high-gradient (2.7 kG/cm) magnetic atom guide. We characterize the parameters for which the open-channel imaging method performs best. Results of quantum Monte Carlo simulations verify the underlying assumptions of the method.     

Spectroscopic study of a representative polar cap of buckminsterfullerene: Cyclopentacorannulene

The spectroscopic properties of corannulene and cyclopentacorannulene are examined by use of absorption and steady-state fluorescence measurements. A red shift in the emission maxima of cyclopentacorannulene is noted with respect to the emission maxima in the corannulene spectrum. Similar differences in the absorption spectra of both molecules are also observed. Reasons for the dissimilarities in the absorption and emission spectra of these molecules are discussed. The fluorescence quantum yields and lifetimes of the molecules measured in organic solvents are reported. The fluorescence quantum yield and lifetime of cyclopentacorannulene are lower than those of corannulene. This difference is attributed to the highly strained and nonplanar structure of cyclopentacorannulene. The effectiveness of nitromethane as a quencher of corannulene and cyclopentacorannulene fluorescence is examined. In contrast to previously reported results, the fluorescence of these molecules is quenched by nitromethane. Fluorescence quenching of the molecules has been attributed to complex formation in the ground state, i.e., static quenching.     

Fluorescence of the <Emphasis Type="Italic">cis</Emphasis>-dimers of porphyrins containing ethylene bridges

The absorption and fluorescence spectra of solutions of the porphyrin dimers containing ethylene bridges, binding two Zn(II)octaethylporphyrin molecules or one Zn(II)octaethylporphyrin and one octaethylporphyrin molecule into cis conformation, were studied. For both studied cis-dimers, structureless absorption spectra were observed, only in general resembling the spectra of initial molecules, as well as weak fluorescence with a wide bell-shaped spectrum with a maximum at 680–700 nm and a quantum yield of about Φ_f≈3×10^?5, which is three orders of magnitude lower as compared to the fluorescence of initial monomeric porphyrins. A strong dependence of the fluorescence yield on a medium viscosity was revealed. In addition, low-yield irreversible cis-trans photoisomerization of cis-dimers was detected. A mechanism responsible for the strong intramolecular quenching of fluorescence of the porphyrin dimers containing ethylene bridges is suggested to be a conformation transformation in the region of the ethylene bridge, leading the molecular system to the region of “conic crossing” of the energy surfaces of excited and ground electron states.     

Quantum diffusion in solid H2?Ne solutions

Quantum diffusion in solid hydrogen containing 0.02–0.25 mol.% neon has been investigated by the calorimetric method in temperature range 1–3 K. The concentrations of orthohydrogen were 0.23; 0.5 and 1 mol. %. The parameter studied was characteristic configurational relaxation time τ. Heat capacity is very sensitive to space distribution of orthohydrogen molecules. Therefore, the determination of configuration relaxation rate has been performed by observing the time dependence of heat capacity. A neon impurity in the indicated concentration is observed to accelerate quantum diffusion in hydrogen. The magnitude of the effect diminishes as the temperature increases.     

Quantum plasmonics with quantum dot-metal nanoparticle molecules: influence of the Fano effect on photon statistics

We study theoretically the quantum optical properties of hybrid molecules composed of an individual quantum dot and a metallic nanoparticle. We calculate the resonance fluorescence of this composite system. Its incoherent part, arising from nonlinear quantum processes, is enhanced by more than 2 orders of magnitude as compared to that of the dot alone. The coupling between the two systems gives rise to a Fano interference effect which strongly influences the quantum statistical properties of the scattered photons: a small frequency shift of the incident light field may cause changes in the intensity correlation function of the scattered field of orders of magnitude. The system opens a good perspective for applications in active metamaterials and ultracompact single-photon devices.     

Optical fractionation of an ensemble of impurity molecules with respect to the magnitude of the piezochromic effect

A method of hole burning in the 0-0 band of the impurity-absorption spectra of polymers and glasses is suggested. This method is selective not only with respect to the transition energy, but also with respect to the magnitude of the piezochromic effect. It is shown that, in combination with the modulation of the wavelength of probe radiation, this method makes it possible to determine the contribution of the impurity molecules with a specified magnitude of the piezochromic effect to the total absorption and luminescence of a sample. This circumstance allows one to study experimentally the correlation of the piezochromic effect with other characteristics of impurity molecules.     

Measurement of Absolute Fluorescence Quantum Yield of Basic Fuchsin Solution Using a Dual-Beam Thermal Lens Technique

The dual beam thermal lens technique is an effective method for the measurement of fluorescence quantum yield of dye solutions. The concentration-dependent quantum yield of a novel dye of triaminotriphenylmethane family in ethanol is studied using this technique. The absolute fluorescence quantum yield is measured and is observed that the reduction in the quantum yield is due to the non-radiative relaxation of the absorbed energy.