Luminescence of europium-doped anode oxide films on titanium-aluminum composites

The luminescence of europium in anode oxide films (AOF) on titanium-aluminum film composites is investigated. It is shown that the intensity distribution in the continuous and line luminescence spectra of europium introduced into the AOF directly in the process of anodic oxidation essentially depends on the sequence of arrangement of the layers of metal films and on the temperature of their heat treatment preceding the process of anodic oxidation. It is established that the nature of the luminescence spectrum of the AOF correlates with the chronovoltammetry diagrams of anodic oxidation. Composites with a high degree of europium doping are found and methods of searching for composites for creating new materials of electronic technology are outlined. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 2, pp. 270–272, March–April, 2000.     

Investigation of uranyl nitrate extraction from ketone solutions by dimethyl sulfoxide

Based on an analysis of low-temperature luminescence spectra (T=77 K) of UO₂(NO₃)₂·6H₂O solutions in acetone, the mechanisms of formation of a wide group of uranyl complexes in uranyl extraction from solutions by dimethyl sulfoxide are studied. It is shown that to increase the coefficient of uranyl distribution between the solution and solid phase (in the form of UO₂(NO₃)₂·2DMSO) it is necessary to add sulfoxide in small amounts, of about 0.35–0.5 mole per mole of uranyl. One-time introduction of DMSO in amounts of 1–3 mole per mole of uranyl leads to the formation of a number of uranyl complexes that are well soluble in acetone, and to a corresponding decrease in the distribution coefficient. The role of entropy and enthalpy in improvement of the stability of chelate complexes of uranyl nitrate is evaluated. Belarusian State University, 4, F. Skorina Ave., Minsk, 220050, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 3, pp. 358–362, May–Jene, 1997.     

Anti-stokes luminescence of solid AgCl<Subscript>0.95</Subscript>I<Subscript>0.05</Subscript> solutions

An anti-Stokes luminescence band with λ_max = 515 nm of microcrystals of solid AgCl_0.95I_0.05 solutions excited by a radiation flux of density 10¹³–10¹⁵ quanta/cm²·sec in the range 600–800 nm at 77 K was detected. It is shown that the intensity of this luminescence and the frequency of its excitation depend on the prior UV-irradiation of samples. Analysis of the stimulated-photoluminescence spectra and the anti-Stokes luminescence excitation spectra of the indicated microcrystals has shown that to the centers of anti-Stokes luminescence excitation correspond local levels in the forbidden band of the crystals. These states are apparently due to the atomic and molecular disperse silver particles that can be inherent in character or formed as a result of a low-temperature photochemical process. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 6, pp. 738–742, November–December, 2005.     

Electronic excitations of Sc3+ impurity in α-Al2O3 crystals

Optical properties, including luminescence, of scandium-doped α-Al₂O₃ crystals have been studied in the VUV range. An absorption band associated with the scandium impurity was observed at the fundamental-absorption edge of crystalline corundum. A strong luminescence band peaking at 5.6 eV, which is most effectively excited within the 7.7–8.8-eV interval, was found. The kinetic and polarization characteristics of this luminescence were studied within the temperature range 6–500 K. An excitation model of the impurity complex and the mechanism of its relaxation are discussed. Fiz. Tverd. Tela (St. Petersburg) 40, 653–654 (April 1998)     

Luminescence detection of multiphoton ionization-fragmentation of the molecular CrO 4 2− anions adsorbed on the surface of dispersed SiO2

It is shown that luminescence detection of multiphoton ionization-fragmentation of the molecular CrO ₄ ²⁻ anions adsorbed on the surface of dispersed SiO₂ is possible under excitation with the fundamental frequency of a Nd:YAG pulsed laser (λ=1.064 μm). The structure and the process of formation of the adsorbed complexes under thermal activation of the surface and the nature of luminescence transitions in CrO ₄ ²⁻ anions are studied in detail. It is shown that luminescence is excited as a result of the recombination of photoelectrons and ionized chromate ions. Multiphoton ionization of the ions occurs under three-photon resonance conditions. The resonance level is an antibonding state of the adsorption complex formed with the participation of an oxygen vacancy on the SiO₂ surface. The dynamics of the multiphoton luminescence excitation process includes autoionization (stimulated by intercomplex electronic excitation) in superexcited states, fragmentation of chromate anions, and annealing of surface oxygen vacancies. The rate equations for three-photon-resonance multiphoton ionization are studied. The cross sections for two-and one-photon transitions on the nonresonance steps of multiphoton absorption are obtained. It is concluded that the nonlinear polarizability of the donor-acceptor adsorption bond in “chromate anion-oxygen vacancy” complexes is very important. Zh. éksp. Teor. Fiz. 111, 1748–1774 (May 1997)     

Anti-stokes luminescence of Zn<Subscript>0.6</Subscript>Cd<Subscript>0.4</Subscript>S solid solutions with adsorbed organic dye molecules and few-atom silver clusters

For microcrystals of Zn_0.6Cd_0.4S with adsorbed molecules of a number of organic dyes, we have observed sensitized anti-Stokes luminescence excited by radiation with wavelengths in the range 610–750 nm and flux density 10¹⁴–10¹⁵ photons/cm²·sec. The positions of the bands in the excitation spectra for such luminescence match those of the absorption spectra for the adsorbed dye molecules, which is evidence in favor of a cooperative mechanism for its appearance. We have shown that enhancement of the anti-Stokes luminescence is possible when silver atoms and few-atom clusters appear on the Zn_0.6Cd_0.4S surface in addition to the dye molecules. We hypothesize that its excitation in the latter case occurs as a result of two-photon optical transitions. These transitions occur sequentially, with transfer of an electron or the electronic excitation energy from the dye molecules to silver atoms and few-atom clusters adsorbed on the surface of Zn_0.6Cd_0.4S, creating deep localized states in the bandgap with photoionization energies 1.80–2.00 eV. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 5, pp. 617–621, September–October, 2007.     

Spectral-luminescent parameters of the amniotic fluid

Absorption and luminescence excitation and emission spectra of the amniotic fluid from females with a normal course of pregnancy and with fetation anomalies are investigated. It is shown that the amniotic fluid manifests, in addition to an intense UV luminescence, a luminescence in the range of 380–650 nm. The first luminescence peak with λ_max = 430–450 nm is most likely due to the presence of NADH₂ and hormones in the amniotic fluid, whereas the peak located at longer wavelengths with λ_max = 520–540 nm is due to pigments (bilirubin, etc.). Differences in absorption spectra of the amniotic fluid in the case of the normal course of pregnancy and upon its pathologies are established. Luminescence emission and excitation spectra of the amniotic fluid in cases of intrauterine fetation pathologies are shifted toward the longwave region compared to normal pregnancy cases. It is concluded that the spectral-luminescent analysis of the amniotic fluid can be used as an additional rapid test for monitoring of intrauterine fetal pathologies. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 6, pp. 939–942, November–December, 1998.     

Luminescence Properties of Metal(II)-Diethyldithiocarbamate Chelate Complex Particles and Its Analytical Application

In a suitable pH buffer solutions, sodium diethyldithiocarbamate (DDTC) reacts with some divalence metal ions M(II) to form (M–DDTC) _n chelate complex nanoparticles, which exhibit different luminescence properties. There is a strongest luminescence peak at 470 nm for the Co(II)–DDTC system, three peaks at 330, 470, and 630 nm for the Cu(II)–DDTC system, three peaks at 420, 470, and 630 nm for the Cd(II)–DDTC system, four peaks at 350, 400, 435, and 470 nm for the Ni(II)–DDTC system, two peaks at 408 and 470 nm for the Pb(II)–DDTC system, two peaks at 415 and 470 nm for the Fe(II)–DDTC system. The different luminescence properties of (M–DDTC) _n chelate complex nanoparticles was explained. Under the optimal conditions, the luminescence intensity of (Co–DDTC) _n chelate complex nanoparticles at 470 nm (F _{470 nm}) is linear to Co(II) concentration in the range of 0.012–1.44 μg/mL. The detection limit is 0.0023 μg/mL. A novel luminescence method has been proposed for the determination of cobalt in Vitamin B₁₂ samples, with satisfactory results.     

Role of highly efficient collisions in collisional transfer of vibrational energy in benzophenone-foreign gas mixtures

Collisional losses of vibrational energy in mixtures of benzophenone excited by nitrogen laser radiation (λ=337 nm) and foreign gases (Ar, Kr, SF₆, C₅H₁₂) were studied by time-resolved delayed luminescence. It is established that the intensities and rates of decay of the fast and slow components of delayed luminescence can be used to evaluate the characteristics of V–V– and V–T–transfer of vibrational energy. For the V-V-process, the efficiencies and mean energies transferred in a collision are determined. It is shown that in the mixture with multiatomic gases, vibrational equilibrium is reached after a few collisions, the number of which decreases as the molecule of the foreign gas becomes more complicated. The V–V–process is characterized by high efficiencies of collisions typical for “supercollisions”. The experimental characteristics of V-V-transfer correlate well with ergodic transfer of vibrational energy predicted by statistical theories. 0120 0126 V 3 Institute of Molecular and Atomic Physics of the National Academy of Science of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 3, pp. 340–345, May–June, 1998.     

Investigation of the interaction of sodium nitrite with hydrogen peroxide in aqueous solutions by the chemiluminescence method

An investigation is made of the chemiluminescence (luminol-dependent and spontaneous) of aqueous solutions of NaNO₂ and H₂O₂ in the pH range of 4.0–9.0. In the presence of luminol at pH>7 the initiator of luminescence is H₂O₂. At pH<7 the luminescence revealed seems to be initiated by peroxynitric acid (HOONO) produced by the interaction of NaNO₂ with H₂O₂ in weakly acid and acid solutions. Cysteine added to the solution prior to introducing H₂O₂ completely suppresses luminescence development in the pH range investigated. Moreover, cysteine quenches the luminescence already developed. Mannite and ethanol do not exert a substantial influence on the development of the luminescence. The solution of NaNO₂ and H₂O₂ is also characterized by spontaneous chemiluminescence, the intensity of which is one-two orders of magnitude lower than that of the luminol-dependent chemiluminescence. The intensity of the spontaneous chemiluminescence of the solutions of NaNO₂ and H₂O attains its maximum in the pH region of 6.5 to 7.0. It is assumed that the revealed spontaneous luminescence of the solutions of NaNO₂ and H₂O₂ is also attributable to formation of peroxynitrit acid in an activated state (HOONO^*). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 3, pp. 436–440, May–June, 1999.     

Intrinsic luminescence of amorphous and disordered crystalline systems

A unified method is developed for describing the steady-state luminescence of exciton fluctuation states for weak excitation in different disordered systems. The phononless luminescence band is found to be formed by “radiative” states of the fluctuation tail in the density of states, i.e., by states for which nonradiative states are either nonexistent or have a low probability. The shape of the emission spectra calculated including the phonon interaction is in good agreement with experimental luminescence spectra of α Si:H and of solid solutions of ZnSe_(1−c)Te_c and CdS_(1−c)Se_c. Fiz. Tverd. Tela (St. Petersburg) 40, 890–891 (May 1998)     

Luminescence quenching of lanthanides in complexes with β-diketones containing different fluorinated radicals

It is shown that luminescence quenching of lanthanide (Ln) ions by water molecules (OH-oscillators) entering the first coordination sphere of a complex decreases as the chain of the fluorinated radical lengthens from CF₃ to C₆F₁₃. The amounts of water molecules in binary and different-ligand Eu complexes with some fluoro derivatives of acetyl acetone are determined. It is established that, unlike OH-oscillators, the elimination of hydrogen oscillations at the central carbon atom by β-diketone deuteration provides the same increase (1.1–1.2 fold) in luminescence intensity in all the investigated Eu complex compounds. A. V. Bogatskii Physicotechnical Institute, National Academy of Sciences of Ukraine, 86, Lyustdorfskaya Read, Odessa, 270080, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 2, pp. 217–220, March–April, 1997.     

X-ray luminescence of disperse SiO2 and porous silicon

We carry out a comparison between the luminescence spectra (photo-and x-ray luminescence) of porous silicon and disperse SiO₂, which by its physical characteristics is most similar to oxide films on porous silicon. The photoluminescence of porous silicon was also investigated using fluorescence (excitation by a nitrogen laser) and metallographic microscopes. We found that the natures of the luminescence centers of porous silicon and disperse SiO₂ are identical. A porous layer on single-crystal silicon ensures the creation of a highly branched surface of oxide film. Luminescence centers are located on its inner (as viewed from the porous silicon) surface. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 2, pp. 247–251, March–April, 1998.     

Luminescence of mercurylike impurities in single-crystal CdWO4 compounds

The processes of crystallization by the method of liquid epitaxy are studied for the first time for single-crystal films of CdWO₄ doped with the mercurylike ions Bi³⁺ and Pb²⁺, which can be used as thin-film components of combined scintillators for monitoring α- and β-activities. It is shown that in comparison with their solidcrystal analogs, the special features of these films consist in a longwave shift of the integral luminescence spectrum that is caused by high concentrations of the radiating complexes (V_Cd-WO₆) with hv_max=2.05–2.15 eV and the “distorted” complexes (WO₆)^* in them. It is found that in the case of luminescence of single-crystal films CdWO₄:Pb, radiation of mercurylike centers (PbO₆) prevails with hv_max=2.87 eV, while in luminescence of CdWO4, radiation of centers (BiO₆) with hv_max=2.16 eV and of complexes (V_Cd-WO₆). Institute of Applied Physics, Iv. Franko Lvov State University, 49, General Chuprynka St., Lvov, 290044, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 2, pp. 211–215, March–April, 1998.     

Luminescence of short-lived color centers induced in LiF crystals by a pulsed microwave discharge

A new phenomenon — intense luminescence of noncolored lithium fluoride (LiF) crystals excited by an electrodeless pulsed microwave discharge at the prebreakdown stage of development — is observed. This luminescence consists of the luminescence of short-lived aggregate F₂ and F ₃ ⁺ color centers at room temperature. It is shown that the density of short-lived color centers induced in the surface layer of LiF crystals by a microsecond microwave discharge reaches values of ∼10¹⁹−10²⁰ cm⁻³. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 3, 163–167 (10 August 1997)     

Luminescent properties of crystalline lithium triborate LiB3O5

A study of the luminescence characteristics of crystalline lithium triborate LiB₃O₅ (LBO) is reported. Investigation of the excitation and photoluminescence spectra of nominally pure, oriented LBO crystals within broad spectral (1.2–10.5 eV) and temperature (8–500 K) regions, complemented by optical spectroscopy at the long-wavelength fundamental-absorption edge, has revealed that the broad-band LBO luminescence in the 3.5–4.5-eV region is efficiently excited by photons having energies above 7.5 eV in recombination processes and under corpuscular or x-ray irradiation. The totality of the experimental data obtained permitted a conclusion that the LBO luminescence has an intrinsic nature and that it originates from radiative decay of relaxed electronic excitations. Fiz. Tverd. Tela (St. Petersburg) 41, 223–228 (February 1999)     

Thermally stimulated luminescence of yttrium oxide in a transparent dielectric medium

The thermally stimulated luminescence of Y₂O₃ in contact with a dielectric is investigated. The measurements were carried out in an atmosphere of dry air, in glycerol, ethylene glycol, and water. Shifting of the spectrum of thermally stimulated luminescence and decrease in the luminescence intensity with an increase in the dielectric constant of the medium were revealed. A discussion of the results is presented. I. I. Mechnikov Odessa State University, 2, Dvoryanskaya St., Odessa, 270026, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 3, pp. 462–463, May–June, 1998.     

Low-voltage low-temperature electroluminescence of CdF2-RE thin films

Different electroluminescence spectrums of the blueλ _max =420 nm wide-banded low-temperature low-voltage radiation of CdF₂-RE films at different levels of excitation in the region of temperatures of 77–300K are investigated. The kinetic characteristics and temperature dependence of this radiation are explored. An effect of the resonance interaction of the centers of luminescence of the wide-band and line radiation of the RE-centers is found. A model of the center of the wide-band radiation is suggested. It is shown that the “blue” radiation is caused by recombination of the carriers. Institute of Physics of Semiconductors of the National Academy of Sciences of Ukraine, Nauka Ave., 45, 252028, Kiev. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 1, pp. 127–132, January–February, 1999.     

Determination of the rate constant of oxygen quenching of the excited states of molecules from the singlet oxygen luminescence

We have pioneered a method of determining the rate constant of quenching of the excited electronic states of molecules by molecular oxygen from measurements of the kinetics of photosensitized luminescence of singlet molecular oxygen (^lδ_g). The method can be used in the case where the lifetime of the excited electronic state in an air-saturated solution is comparable with or larger than the luminescence time of the singlet molecular oxygen in the given solvent. It is shown that this situation is implemented on quenching, by molecular oxygen, of the excited triplet states associated with the biopolymers of tetrapyrrole molecules in aqueous (H₂O and D₂O) solutions. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 3, pp. 401–404, May–June, 2000.     

Optical spectra and a tail in the density of states of the disordered solid solution ZnSe1−c Tec

A calculational scheme is presented to determine the density of states in the fluctuation tail for the disordered solid solution ZnSe_1−c Te_c at concentrations below the threshold for percolation over sublattice sites. Zero-phonon absorption and luminescence bands in the region of the exciton ground state are found using an approach developed earlier. Phonon coupling is taken into account, and vibronic absorption and luminescence bands are obtained. Experimental data are shown to be in a good agreement with the calculations. Fiz. Tverd. Tela (St. Petersburg) 40, 1420–1425 (August 1998)