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This research project was supported by the Polish National Science Centre (Grant DEC-2011/03/B/ ST10/06320) and by statutory funding from the Faculty of Earth Sciences at the University of Silesia. Dr. Padhraig S. Kennan (University College Dublin, Ireland) is thanked for help with language., The electron absorption-, photoluminescence- and electron paramagnetic-resonance spectra of Mn3+ in red beryl from Wah Wah Mountains (Utah USA) and of pink- and purple vesuvianite from Jeffrey Mine (Asbestos, Canada) were measured at room- and low temperatures. The crystal field stabilization energies are equal to 130.9 kJ/mol for the red beryl, and 151.5–158.0 and 168.0 kJ/mol for for the pink- and the purple vesuvianite, respectively. The red photoluminescence of Mn3+ was not intensive either at room- or at low temperatures. The high Mn content in the crystals caused the emergence of an additional emission band and short photoluminescence-decay lifetimes. The latter are only 183 μs for beryl and 17 μs for vesuvianite., Narodowe Centrum Nauki

We have investigated the thermal and spectroscopic properties of Pr3+-doped new tellurite matrix with the molar composition 60%TeO2–27%WO3–10%PbO–3%Lu2O3 (TWPLu). The differential thermal analysis has shown that addition of Lu2O3 to the glass results in an increasing resistance against crystallization. The ellipsometric data have provided a Sellmeier-type dispersion relations of the refractive index of the investigated glasses. The optical absorption edge of the TWPLu matrix has been described within the Urbach approach, while the absorption and fluorescence spectra of the Pr3+-doped TWPLu glasses have been analyzed in terms of the standard Judd–Ofelt theory along with the luminescence decay of the 3P0 and 1D2 levels of the Pr3+ ion. A significant influence of the Pr3+ ion concentration on the photoluminescence intensity as well as on decrease of the lifetimes of both levels has been explained by a non-radiative energy transfer between the ions through cross-relaxation and energy migration processes.

The subject of our investigation was the intensity of the fluorescence of 1,4,5,8-naphtalisoimides subjected to gamma radiation (the absorbed doses were 242 Gy, 1 kGy and 2.242 kGy). Dynamic changes of fluorescence intensity have been observed; the greatest relative increase of fluorescence intensity (and simultaneously, the least durable increase) occurs as a result of structural isomerisation.

Presented herein are the luminescence properties of several 1,4,5,8- polinahthalisoimides. The luminescence decay curves after deconvolution exhibit three decay times: τ1, τ2, and τ3.The luminescence lifetimes change along with the growth of excitation energy, as well as the contribution of each luminescence decay mechanism (A1, A2, and A3). The manner of change is distinct for one sample, namely, the pure E-isomer, in comparison to the others. The radiative deexcitation coupled with radiationless vibrational energy transfer to other luminescence centers, mainly other isomer units, is discussed as a possible deexcitation mechanism of fluorescence. The Kasha–Vavilov empirical rule is not fulfilled for the studied samples, as the luminescence quantum efficiency (ΦF) distinctly depends on the excitation wavelength (λexc). The quantum yield of one sample (about 63% of Z-isomer) is quite high, at 1%.

For the first time, the photoluminescence of ions of Ce3+ and Eu2+ in natural low-P ternesite has been measured. The emission bands of Ce3+ ions at 405, 426, and 440 nm and the corresponding excitation wavelengths suggest the presence of Ce3+ ions in three different cationic sites. In the photoluminescence spectra of Eu2+, emission bands at 530 and 620 nm can be seen that originate from two different cationic sites. In addition, it is demonstrated that an energy transfer occurs between Ce3+ and Eu2+ ions situated in those cationic sites where the force of the crystallic field is weakest. The photoluminescence spectra were obtained for a thin section sample with low contents of these two elements (41.2 ppm Ce, 2.11 ppm Eu).

The purpose of this work was to investigate the spectroscopic properties of Pr 3 + ions of various concentrations embedded in a new matrix, namely a tellurite–tungstate glass with the molar composition 60%TeO 2 –27%WO 3 –10%PbO–3%La 2 O 3 (TWPLa). The optical absorption edge of the TWPLa matrix has been described within the Urbach approach, while the absorption and fluorescence spectra of the Pr 3 + -doped TWPLa glasses have been analyzed in terms of the standard Judd–Ofelt (J–O) theory along with the luminescence decay of the 3 P 0 and 1 D 2 levels of the Pr 3 + ion. A significant influence of the Pr 3 + ion concentration on the photoluminescence intensity as well as on decrease of the lifetimes of both levels has been explained by a non-radiative energy transfer between the ions through different cross-relaxation channels. The spectroscopic studies have been completed with ellipsometric measurements providing the dispersion relation of the refractive index of the investigated glasses that has been taken into account in the J–O analysis.

For the first time ever, the luminescence spectra of Cr3+ centers in two chlorite crystals are presented. Chromium ions occupy the strong crystal-field site M4 in the brucite sheet and the intermediate crystal-field site in the inner octahedral sheet for purple and green chlorite, respectively. We discuss the influence of an effective positive charge on the Cr3+ ion and an effective negative charge of ligands on the differences in the values of the Dq and B parameters. It is concluded that the presence of Fe2+ ions and other point defects, as well as concentration quenching, causes the very short luminescence lifetimes of chromium ions.

Multicomponent telluride-tungstate glasses containing Nd 3+ and Er 3+ ions were studied experimentally at 77 and 293 K using spectroscopic methods. The Judd–Ofelt intensity parameters were derived from the absorption spectra and used to calculate the radiative lifetimes and branching ratios. The quantum efficiency η = 0.95 of the 4 F 3/2 level of Nd 3+ ion is higher than the typical value of other tellurite-based glasses. For low concentration of Er 3+ ions, the luminescence decay of the 4 S 3/2 and 4 I 11/2 levels is governed by radiative transitions and multiphonon relaxation involving the Te-O highest energy vibrations.

We report absorption and first reliable photoluminescence (PL) studies at various temperatures on relatively thick films of the basic polyazomethine — PPI, i.e., poly(1,4-phenylene-methylidynenitrilo-1,4-phenylenenitrilomethylidine), prepared by chemical vapor deposition (CVD). Both absorption and PL spectra exhibit the vibronic progression due to the C–C stretching mode, characteristic for conjugated polymers. The absorption spectra appear to be practically temperature independent, in contrast to PL spectra, the intensity of which strongly decreases with increasing temperature. The origin of generally weak photoluminescence of PPI is suggested to be the result of a non-radiative electronic state occupied by the lone electron pair on the nitrogen orbital.

A P 2 O 5 -CaO-SrO-BaO phosphate glass doped with Tm 3+ and glasses doped with (Tm 3+ , Pr 3+ ) were used for this study. The photo-luminescence behaviors of Tm 3+ and Pr 3+ in phosphate glass were investigated by absorption, excitation and emission spectroscopy. The energy transfer between Tm 3+ and Pr 3+ in phosphate glasses (which exhibit a variety of transfer efficiencies) was studied. The experimental quantum efficiencies of the luminescence of Tm 3 + η 0 and (Tm 3+ , Pr 3+ ) doped phosphate glasses were measured to give η/η 0 = 0.447, 0.305, and 0.179 for (0.4 mol% Pr 3+ , 1.0 mol% Tm 3+ ), (0.8%Pr 3+ , 1.0%Tm 3+ ) and (1.6 mol% Pr 3+ , 1.0 mol% Tm 3+ ), respectively. In order to verify the nature of the ion coupling in our phosphate glass system, we applied the Inokuti–Hirayama model. The non-radiative energy transfer rate from Tm 3+ to Pr 3+ , transfer efficiencies, and the donor–acceptor distance have been calculated and compared with obtained experimental data. As usual, the efficiency and the probability of energy transfer increase with the concentration of the acceptor.

In this paper, we present the photoluminescence properties of Pr3+, Sm3+ and Er3+ doped phosphate glasses. Optical absorption and emission spectra of lanthanide active ions in P2O5–CaO–SrO–BaO glass have been investigated at room temperature. These glasses have shown strong absorption bands in the near-infrared (NIR) and visible (VIS) region. For Pr3+ doped glass, emission bands centered at 608 nm (3P0 → 3H6 + 1D2 − 3H4), 640 nm (3P0 → 3F2), 686 nm (3P0–3F3) and 723 nm (3P0 → 3F4) have been observed with 480 nm (3H4 → 3P0) excitation wavelength. Of them, 686 nm has shown bright red emission. Emission bands of (4G5/2 → 6H5/2) 560 nm, (4G5/2 → 6H7/2) 600 nm and (4G5/2 → 6H9/2) 645 nm for the Sm3+ phosphate glass, with excitation at (6H5/2 → 4F7/2) 400 nm have been recorded. With regard to the Er3+ phosphate glass, a bright fluorescent green–yellow emission at 546 nm (4S3/2 → 4I15/2) have been observed. Analysis of decay curves of luminescence revealed occurrence of the strong luminescence quenching originating from the 3P0 metastable level of Pr3+ and 4S3/2 state of Er3+ mainly by a multiphonon relaxation processes to 1D2, 4F9/2 levels respectively. Moreover these results are compared with those obtained by using the Judd–Ofelt theory. According to the Judd–Ofelt theory, the Judd–Ofelt intensity parameters Ω2,4,6 were calculated, by which the radiative transition probabilities and radiative lifetimes of luminescent levels were obtained.

The luminescence spectra of Pr3+ and Sm3+ ions in apatite Ca5[F∣(PO4)3] crystals from Spain and Russia have been compared with those for phosphate glasses doped with Pr3+, Sm3+ and Pr3+, Sm3+ ions. Time-resolved spectra measurements confirm that, in apatites, samarium ions occupy two non-equivalent crystal sites; the same is assumed for praseodymium ions. For the first time in minerals, the Stark splitting energy levels ΔE for 3H6 and 1D2 of Pr3+ ion and 6H7/2 of Sm3+ ion were determined. Some small differences in ΔE values for the Spanish and Russian apatite are discussed. The decay times of the excited levels of Pr3+, Sm3+ and Pr3+, Sm3+ doped in phosphate glass were measured at room temperature and at 77 K. The energy transfer process between samarium and praseodymium ions was observed and the energy transfer rate was calculated.

The Judd–Ofelt (J–O) theory has had a remarkable success in the characterization of radiative transitions in lanthanide doped solids. The purpose of this paper is to review the applications of the J–O theory to the Pr3+ and Sm3+ ions and to use this system as an occasion to appraise its validity and to clarify its limits. In this paper we dwell at length on the absorption and luminescence measurements of two glass samples doped with Pr3+ and Sm3+, because they are basic for the J–O treatment. The results obtained for the J–O theory application to phosphate glasses doped with Pr3+ and Sm3+ present two undesirable outcomes: (1) a positive value of parameter Ω2 and (2) large uncertainties with which the three Judd–Ofelt parameters were obtained. The validity of the J–O theory for intensity analysis was also tested for Sm3+ doped in phosphate glass. The resulting Ω2 was much lower than Ω4. The first set parameters were obtained using all the levels for which fexp. was available. The second set parameter values were evaluated without the 6F1/2 and 6H15/2 levels. The Ω2,4,6 values given in these two sets clearly suggest that particular care should be taken while evaluating the Judd–Ofelt parameters as well as when these parameters are compared to other systems due to their strong dependence on the nature of levels.

Supramolecular aggregations have been obtained via ionic self-assembly of conjugated poly(ketanil)s and sulfonic acid derivatives of benzenetricarboxamides. To achieve this goal a new protonating molecule has been synthesized which is a derivative of 1,3,5-benzenetricarboxamide with sulfonic acid group at each of its ends. 1,3,5-benzenetricarboxamides of C3 symmetry tend to form ordered supramolecular aggregations via π-stacking and this property is retained in their sulfonic acid derivative. Because of their Bronsted acid nature the new molecules can additionally associate conjugated polymers with basic centers such as poly(ketanil)s. Depending on the processing solvent used (MC or DMA) 1,3,5- the sulfonic acid derivative of benzenetricarboxamide and its associations with poly(ketanil)s form aggregations of spherullite-like or feather-like morphologies as evidenced by polarized optical microscopy and atomic force microscopy. The similarity of this supramolecular organization is also corroborated by DSC studies which in both cases show endothermic type transitions of the same origin. The supramolecular acid–base associations are semi-crystalline in nature and exhibit good mechanical properties at room temperature because of a rather low Tg, in the vicinity of 300 K. This unusual lowering of Tg by ca. 90 K as compared to the case of poly(ketanil)s in their basic form is caused by the plasticizing effect of the protonating agent. Finally polyketanil–1,3,5-benzenetricarboxamide sulfonic acid derivatives show tunable photoluminescence which depends on the solvent and SO3H/C N molar ratio.

A series of six conjugated aromatic polyazomethines has been obtained by high-temperature solution polycondensation of diformyltriphenylamine with different primary aromatic diamines. The structures of polymers are characterized by means FTIR, 1H NMR, and 13C NMR spectroscopy and elemental analysis; the results show an agreement with the proposed structure. Polyazomethines emitted blue or blue-green light. Relative PL intensity of the polymers investigated in chloroform solution was found about 0.30%, while for doped ones it was about 20% in relation to 9,10-diphenylanthracene. Additionally, the photoluminescence spectra of the polyazomethines in polymer blend with poly(methyl methacrylate) (PMMA) have also been described. The lowest optical band gap value at 2.41 eV was detected. Polymers were investigated also by cyclic voltametry and differential pulse voltammetry in dichloromethane. An influence of different types of dopants, i.e., methanesulfonic acid (MSA), camphorsulfonic acid (CSA), m-cresol (MC),...

Relationship between structures and properties of new conjugated polyketanils (PKs) with special architectures, synthesized from three diketones, i.e. p-dibenzoylbenzene, dibenzyl, trans-1,2-dibenzoylethylene and 3,8-diamino-6-phenylphenanthridine, was investigated. The photoluminescence (PL) of green, yellow and red emitting light polymers and their blend was studied. These included the effects of excitation wavelength, concentration and film thickness on the PL. Photoluminescence properties of the PKs before and after protonation with 10-Camphorsulfonic acid (CSA) were tested. The structure formation of (PKs)1(CSA)2 complexes are discussed on the basis of FTIR spectroscopy.

The optical properties of polyimines (PAs) with structure containing aliphatic-aromatic and aromatic-aromatic moieties are reported. It is demonstrated that the photoluminescence (PL) spectra can be regulated over a wide range by variation in main chain structure and through protonation or intramolecular hydrogen bonding. By combining these two methods it is possible to precisely tune the emission spectra of PAs in the spectral range of 480-531 nm. Luminescent PA/1,3,5-benzenetricarboxamide sulfonic acid complexes were self-organizated from nonamphiphilic n-conjugated PAs, in DMA and in m-cresol solution. Solvatochromism is manifested in the PL spectra of the undoped and doped PAs. The emission spectra of doped PAs are blue or red shifted relative to the undoped one. Additionally, absorption (UV-vis) properties of the PAs before and after protonation with 1,3,5-benzenetricarboxamide sulfonic acid ('dopant I') were tested. We propose that the novel self-assembly is driven by the amphiphilicity of 1,3,5-benzenetricarboxamide sulfonic acid activated by protonation of PAs.

Results of X-ray diffraction, infrared spectroscopy, differential scanning calorimetry and optical emission together with lifetime measurements of phosphate fluoroindate glasses activated by Pr3+ ions are reported. Structural, thermal and optical behavior of multicomponent oxyfluoride glasses has been analyzed as a function of P2O5 concentration. Short glass-forming region exists for InF3-based system with P2O5 additives. For low (4–12%) P2O5 concentration, thermally stable and transparent non-crystalline oxyfluoride samples based on InF3 with relatively high ΔT factors were prepared, which can be promising for fiber drawing. For higher (16%) P2O5 concentrations, several diffraction lines due to the InOF polycrystalline phase were identified. Absorption edge and luminescence bands for Pr3+ ions in fluoroindate glasses are shifted in the direction of the lower frequency region with increasing of P2O5 content. Luminescence from both 3P0 and 1D2 excited states of Pr3+ ions was registered. The 1D2 luminescence lifetime close to about 35 μs is independent on P2O5 concentration.

A series of aromatic poly(amideimide)s containing 9,9-diphenylfluorene moieties and the amide units in the main chain have been synthesized by solution polycondensation reaction of newly prepared diamidedianhydride with several aromatic diamines: 1,3-phenylenediamine, 3,3′-dimethoxy-biphenyl-4,4′-diamine, 4,4′-oxydianiline, 4,4′-(1,3-phenylenedioxy)dianiline, 4,4′-(9-fluorenylidene)dianiline and 1,5-diaminonaphthalene. Molecular structures of the polymers obtained have been characterized using 13C NMR, 1H NMR and FTIR spectroscopies. The polymers prepared are readily soluble in aprotic polar solvents, and form optically transparent films by solution casting. The resultant poly(amideimide)s have been analyzed by differential scanning calorimetry (DSC), thermogravimetry (TG) and wide-angle X-ray diffraction measurements. They exhibited high levels of thermal stability, with decomposition temperatures in the range 452–494 °C, and high glass transition temperatures (181–278 °C). The optical behavior of these polymers has been investigated in NMP solution as well as in the films. The photoluminescence (PL) spectra of the free-standing films prepared from the poly(amideimide)s exhibited maximum emission bands around 506–525 nm in the green region.

New luminescent materials - aromatic polyketanils (PKs) containing p-phenylene and biphenylene linkages in the backbone and electron-donating side-group substitutions have been synthesized via melt polycondensation (180°C, 24 h). Their structures were confirmed by elemental and spectral Fourier transform infrared, 13Cand 1H NMR, and ultraviolet-visible (UV-vis) analysis. All the PKs were solution-processable and thermally stable, making them potential candidate materials for applications in microelectronics and aerospace. These ketanil polymers showed high thermal stability and well-defined glass transition temperatures ( Tg). The temperature at which the polymers lose 10% of their weight ( T10) ranged from 420 to 520°C. Depending on the polymer structure, PKs showed Tg values in the range of 133 to 244°C. Moreover, the polymers emit either blue radiation or green radiation depending on the mutual presence of conjugated and saturated chain segments. The HOMO/LUMO energy gap of the polymers was in the range of 2.74-2.19 eV. The photoluminescence properties of the PKs after protonation with DL-camphor-10-sulfonic acid (CSA) were tested. The structure formation of (PKs)1(CSA)2 complexes are discussed on the basis of 1HNMRspectroscopy.

New luminescent materials—aromatic polyketanils (PKs) containing p-phenylene and biphenylene linkages in the backbone and electron-donating, side-group substitutions—were synthesized via melt polycondensation with the goal of studying the interactions between the polymer chains (PKs), primary dopant [1,2-(di-2-ethylhexyl)ester of 4-sulfophthalic acid (PSA)], and secondary dopant [m-cresol (MC)] with 1H NMR, 13C NMR, Fourier transform infrared (FTIR), ultraviolet–visible, and photoluminescence measurements. Spectral changes were observed for the PKs after primary and secondary doping, and they supported ionic- and hydrogen-bond formation between the PKs and the PSA and MC, respectively. This specific interaction of the dopant with the host polymer influenced the PK properties, and the following observations were made: (1) HOMO/LUMO energy gap of the protonated PKs; (2) bathochromic/hypsochromic photoluminescence shifts observed after protonation with PSA; (3) a downfield chemical shift of the labile proton in the protonating agent OH group in the 1H NMR spectra of the protonated polymers; (4) a protonation decrease in the intensity of the CN stretching band in the FTIR spectrum; and (5) a spherulite-like morphology, detected by atomic force microscopy and polarized optical microscopy. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5645–5660, 2006

We have studied the high-field magnetization (up to 14.5 T) and magnetic susceptibility in the temperature range 1.7 - 420 K of two samples of jadeite (NaAlSi2O6), white and green, containing transition metal ions and originating from Burma (now Myanmar). It appears that the high-temperature susceptibility data obey the Curie-Weiss law indicating the onset of the antiferromagnetic interaction between the magnetic ions. This interaction is also seen in the high-field magnetization data which are well described by the phenomenological cluster model. As a result of our analysis, we have identified the Fe3+ ions as the dominant ones in the studied jadeites and we have determined the molar concentration of these ions (0.8% in white- and 2.5% in green jadeite) as well as the diamagnetic susceptibility of the jadeite matrix (-3.8 × 10-7 emu/g).

New oligoketanils containing vinylene group in their main chain have been synthesized from diamines and diketones by melt-condensation (180 °C, 24 h). Physical properties of these new polyconjugated systems can be conveniently tuned either by an appropriate design of the repeat sub-unit originating from the diamine or by protonation of imine nitrogens with a protonating agent exhibiting plasticizing properties, for example with 1,2-(di-2-ethylhexyl)ester of 4-sulfophthalic acid (DEHEPSA). In the base (non-protonated) form they emit either blue radiation or green radiation depending on the mutual presence of conjugated and saturated chain segments. Protonation with DEHEPSA transforms blue radiation emitters into the green radiation ones. Simultaneously it results in a large decrease of the glass transition temperatures (Tg), of the systems investigated, from values exceeding 373 K to values close to room temperature, improving by consequence their flexibility.

New conjugated aryl-substituted poly(azomethine)s, termed poly(ketanil)s, have been synthesised from 1,4-phenylenediamine (or 3,3′,5,5′-tetramethylbenzidine) and two different diketones via polycondensation with the goal to obtain new materials with tunable spectroscopic properties. It is demonstrated that both the absorption and photoluminescence spectra of these poly(ketanil)s can be modified not only by changing the chemical constitution of both repeating subunits in the polymer main chain but also via acid-base doping involving the protonation of the ketimine groups. By combining these two methods it is possible to precisely tune the absorption and emission spectra of the poly(ketanil)s. The use of bifunctional protonating agents, containing plasticising groups, for example 1,2-(di-2-ethylhexyl)ester of 4-sulfophthalic acid (DEHEPSA), in addition to modifying the spectroscopic properties of the polymers, leads to a lowering of their glass transition temperature (Tg), improving in such a manner the flexibility of the prepared poly(ketanil)s materials.

Optical absorption and emission spectra are presented for Pr 3+ and Pr 3+ + Cr 3+ ions in fluoroindate glass. Also, X-ray diffraction (XRD) and differential scanning calorimetry (DSC) measurements are carried out in order to characterize investigated materials. The measured oscillator strengths and radiative rates for several transitions of the Pr 3+ ion are compared with calculated values. Radiative transition rates for the excited states are determined by using the Judd-Ofelt theory. Energy transfer effects account for the non-radiative transitions. Although the Judd-Ofelt analysis does not yield the same excellent consistency for Pr 3+ as for Nd 3+ and Er 3+ , the experimental observations are consistent with Judd-Ofelt calculations. The linear concentration quenching and exponential decay times of the 1 D 2 level are explained assuming cross-relaxation and energy transfer between the Pr 3+ ions. Energy level diagrams of Cr 3+ and Pr 3+ reveal that the 1 G 4 level of Pr 3+ lies close in energy to the 4 T 2 fluorescent level of Cr 3+ , and hence will expect a portion of excitation energy from Cr 3+ . Unfortunately, the mismatch in energy of this Pr 3+ level with the 4 T 2 level of Cr 3+ (∼3000 cm -1 ) cannot be compensated for by the phonons of the host, having an energy of about 500 cm -1 .

A series of semiladder polyimidazopyrrolones having amide, ester and ether linkages in the main chain have been synthesized using low-temperature polycondensation in dimethylacetamide (DMA). Solutions of prepolymers in the form of proper polyamideamino acid in DMA were cast onto a glass plate, heated in vacuo at 200 °C for 8 h and then at 280 °C for 2 h to cause evaporation of the solvent and thermal cyclization. Free-standing foils were characterized by Fourier-transform infrared spectroscopy and their mechanical, thermomechanical and optical properties were investigated.

We have studied the high-field magnetization up to 14.5 T and magnetic susceptibility in the temperature range 1.6–400 K of three different samples of natural kunzite crystals, being a variety of spodumene (LiAlSi2O6) and containing transition metal ions. It appears that the total magnetization and susceptibility consist of the paramagnetic contribution following from the temperature-dependent Brillouin-type behavior of magnetic ions and temperature-independent diamagnetic contribution of the spodumene matrix which we have found as being equal to −3.5×10−7 emu/g. We have identified the Mn2+ ions as the dominant ones in the kunzites studied and we have determined the molar concentration of these ions as lying in the range 0.2–0.4%.

The magnetic susceptibility as well as the optical excitation and luminescence spectra of three samples of α-ZnAl2S4 tiospinel doped with Cr at various concentrations have been measured in the temperature range 77–300 K. The susceptibility has allowed us to estimate the concentration of Cr in the samples studied as lying in the range 0.01–0.06 at.%. Crystal-field theory, including spin–orbit coupling and the trigonal crystal field of the D3d site has been used to fit the optical data. The best-fit parameters of the tiospinel crystal are B20=4800, B40=32500, B43=−28500, F(2)=58800, F(4)=40500 and ξD=300 cm−1. The computational procedure used gives excellent agreement between the experimental and calculated energy levels of the Cr3+ ion in the α-ZnAl2S4 matrix.

The optical excitation and luminescence spectra of (Pr3+,Ce3+) ions in KCaF3 are presented. High-resolution excitation and emission spectra of Pr3+ and Ce3+ were measured at temperatures between 77 and 293 K. First measurements of KCaF3 : Ce3+ crystal show that there are nonequivalent Ce3+ centers which radiate either in UV or visible range. The major Ce3+ nonequivalent center in KCaF3 is Ce3+ ion in the site with tetragonal site symmetry (S4). Energy levels for the 4f2 ground configuration of Pr3+ in KCaF3 were established from excitation and fluorescence spectra. Energy levels assignments were made assuming electric-dipole transition selection rules for S4 site symmetry. Twenty-seven energy levels in the lowest six multiplets of the ground configuration were established. In the analysis of experimental data, the Oh magnetic-dipole selection rules were also considered to explain missing or weak transitions which are allowed in S4. Spectra of Pr3+ in KCaF3 have been analyzed with a crystal-field Hamiltonians of S4 or Oh symmetries including J mixing effects. Crystal-field parameters in these Hamiltonians have been determined by the minimization the RMS deviation between calculated and experimental energy Stark levels. We conclude that both model calculations in the S4 and Oh site symmetries for Pr3+ in KCaF3, provide the basis for a consistently good correlation with data.

It is known that the spectroscopic properties of 3d impurities in crystals are very sensitive to the environment of the ion and can be changed considerably by using different matrices. The crystal structure of KCaF3 has been previously determined by the Rietveld profile method. At room temperature, KCa1−xMnxF3 (x

What do the Civil War battles of Fredericksburg and Gettysburg have to do with the Art of War , the military strategy treatise written by ancient Chinese general Sun Tzu (ca. 544 – ca. 496 BC)? Very much, in fact. The Art of War’s timeless advice and principles can explain the results of battles and entire wars in every historical period, including the 19th century. The unorthodox way of war advocated therein allowed Sun Tzu, the commander of the army of Wu, to defeat a much larger army of the neighboring state of Chu, but due to a lack of English translation until 1910 was unknown to the English-speaking world, including Generals Ambrose Burnside and Robert Lee, who, ignorant of its sage advice, made catastrophic blunders at Fredericksburg and Gettysburg, respectively. Burnside attempted a rapid crossing of the Rappahannock river at Fredericksburg, but pontoon bridges did not arrive in time, so the element of surprise was lost, and even when they did, he hesitated to cross until December 1862 when Confederates had already dug themselves in at Marye’s Heights; he sent his men like swarming ants towards the Confederate trenches on the heights, losing thousands of them. Lee evidently didn’t learn from his enemy’s mistakes and repeated them at Gettysburg in July 1863. Although no river crossing was involved, Lee wrongly abandoned his original plan to capture Harrisburg and Camp Curtin (which would have been a huge prestigeous blow to President Lincoln and might have encouraged a European recognition of the Confederacy) and, upon hearing that Union divisions were at Gettysburg, he moved his entire army there. At Gettysburg, he first issued unclear orders to subordinate Gen. Richard Ewell, then, the next day, clarified these by ordering multiple suicidal assaults on fortified Union positions on Cemetery Ridge. Sun Tzu counseled against attacking an enemy’s strong positions and especially against charging uphill to attack. He also stressed the importance of clarity of orders and of not trying the same type of attack over and over again. As Burnside’s and Lee’s examples show, generals who ignore Sun Tzu’s advice do so at their own peril.

The spectroscopic properties of new luminescence crystal containing Cr 3+ in Ca 3 Al 2 (SiO 4 ) 3 natural garnet (Grossular) measured at different temperature are reported. The spectra have been used for determined energies of R 2 , R 1 , ZPL, vibrational modes and 2 E g , 4 T 2g levels. A relatively large splitting of the 2 E g state of Cr 3+ in grossular is observed. To account for the thermal quenching of the R-lines it is necessary to recognize that the two components of the doublet may have remarkably different radiative lifetimes (6450 and 1075 μs). These lifetimes were obtained from low temperature decay and from the temperature dependence of the intensity ratio of the R 2 , R 1 , components. These separate lifetimes were then set to fit the temperature dependence of the joint effective lifetime and the steady state intensities of both lines.

The optical absorption and luminescence spectra of Cr 3+ in Ca 3 Al 2 (SiO 4 ) 3 natural garnet (Grossular) measured at room and LHeT were reported the first time in Mazurak [Opt. Mater., this issue]. The spectra have been used for determined energies of R 2 , R 1 , ZPL, vibrational modes and 2 E, 4 T 2 , 4 T 1 levels. We have extended our investigations, the spectra of Cr 3+ in Ca 3 Al 2 (SiO 4 ) 3 are analyzed using a C 3i crystal-field Hamiltonian. The energy levels and the crystal-field parameters B nm for Cr 3+ ion in Ca 3 Al 2 (SiO 4 ) 3 single crystal, including spin-orbit and ligand-field interactions, have been calculated. The resulting crystal-field parameters B nm represent very well the crystal-field interactions of Cr 3+ in Grossular Ca 3 Al 2 (SiO 4 ) 3 .

The tellurite-tungstate glasses containing small amounts of rare-earth ions have been studied experimentally at 77 and 293 K using spectroscopic methods. The photoluminescence (PL) studies reveal the emission of efficient green-yellow light from Tb3+ ions and red light from Eu3+ ions. The Judd-Ofelt intensity parameters have been derived for Nd3+ and Er3+ ions from the absorption spectra and they have used to calculate the radiative lifetimes and branching ratios. The quantum efficiency η = 0.95 of the 4F3/2 level of Nd3+ ion is higher than the typical value of other tellurite-based glasses. For Er3+ ions, PL originating from the 4S3/2,4I11/2 and 4I13/2 levels has been observed and the luminescence decay of the first two levels has been found to be governed by radiative transitions and multiphonon relaxation involving the highest energy of Te-O vibrations.

A series of polynaphthalsoimides and polynaphthalimides from 1,4,5,8-naphthalene dianhydride and 4,4'-methylene-bis(2,6-diisopropylaniline) or its hydrochloride in HMPA were synthesized in one-step high temperature polycondensation process. The different temperatures of the reaction from 125°C to 180°C were applied. The products were investigated using PL techniques in both solutions and thin layers. The observed changes in all investigated spectra and photochemical properties were presented. The remarkable changes in emission wavelength in photoluminescence was observed together with the increase of the reaction temperature. This work presents novel approach to the class of polymers well known to literature worldwide trying to explain of some surprising aspects of photoluminescence of these compounds. When investigated in solution, the polymer synthesized at 125°C exhibit almost no photoluminescence. The increase of the temperature to 150°C causes the strong increase in the photoluminescence intensity at 545 nm. When the reaction temperature increase to 180°C the intensity of photoluminescence exhibits moderate increase at 546.5 nm, however, remarkable increase was observed for 476.5 nm and 440 nm. The photoluminescence analysis of the polymers synthesized shows that depending on reaction temperature products emitting at different wavelengths may be obtained. Investigations were repeated for thin layers of the polymers. The obtained results and their comparison with the results in solution were also presented and discussed.

Rare-earth ortho-aluminates having the chemical formula La1-xErxAlO3, with x=0.01, 0.02, 0.05, 0.1, 0.2 have been synthesized. Spectroscopic investigations of the (La,Er) ortho-aluminates have allowed the measurement of luminescence yield and lifetimes of Er3+ excited states in the host lattice as a function of the erbium content. The mechanism of concentration quenching of the Er3+ emission in (La,Er)AlO3 is reported and discussed. The linear concentration quenching and exponential decay times of the 4S 3 2 level are explained assuming cross-relaxation and energy transfer between the Er3+ ions. This behaviour is consistent with the process of the cross-relaxation via an intermediate level. Quenching of luminescence from the 4I 11 2 level in heavily doped samples is attributed to the nonradiative energy transfer from Er3+ ions to structural defects.

FIR absorption in powdered ZnAs2 crystals is studied. The features within the frequency area 194 to 270 cm−1 are attributed to As helix modes. Low-frequency features are attributed to modes involving important contributions of Zn atoms. There are some indications that inter-As helix correlation splitting exists. L'absorption dans l'infrarouge lointain des cristaux en poudre du ZnAs2, est etudiee. Les bandes aux frequences de l'interval 194 a 270 cm−1 sont attribuees aux modes des As helices. Celles aux basses frequences sont attribuees aux modes avec une contribution importante d'atomes du Zn. Il y a des indications qu'un fondage de correlation due aux interactions parmi des As helices peut exister.

New photoluminescence oligoazomethines possessing both hole and electron-transporting units in the main chain were synthesized. Triphenylamine (TPA) was used as the electron-donating group, while 4,4'-diaminooctafluorobiphenyl, 4,4'-(hexafluoro-isopropylidene)dianiline, 4-aminophenylsulfone, 4,4'-(4,4'-isopropylidenediphenyl-1,1'diyldioxy)dianiline and 2,5-bis(4-aminophenyl)-1,3,5-oxadiazole were used as the electron-acceptor or as the electron-donating group. The bifunctional oligomers (D-pi-A and D-pi-D) were soluble in some organic solvents such as chloroform, DMA, HMPA, NMP and formed transparent films on glass support. All oligomers exhibit high glass transition temperature in the range of 188-227 degrees C as determined by differential scanning calorimetry (DSC). The photoluminescence (PL) emission maximum peaks of the oligomers in solution are in the range of 459-552 nm (2.70-2.25 eV) corresponding to blue, blue-green or green light. The solvatochromic and protonation behavior of the oligomers in two solvents (DMA, chloroform) were detected. Oligomers protonated with methanesulfonic acid (MSA) are hypsochromically shifted with respect to the PL spectra of the pristine oligomers measured in solution. Relative PL intensity of the oligomers investigated in chloroform solution was found in the range of 0.10-0.50%, while for protonated ones it was detected in the range of 33-50% in relation to 9,10-diphenylanthracene. Blends of the oligoazomethines with poly(methylmethacrylate) (PMMA) (0.1%, w/w) emitted blue light. Thin films were also doped with iodine. Calculated energy gap for the undoped films following the Tauc relation was in the range of 2.46-2.69 eV while for the iodine doped oligomers in the range of 1.76-2.38 eV was found.

Relationship between structures and properties of new conjugated polyketanils (PKs) with special architectures, synthesized from three diketones, i.e. p-dibenzoylbenzene, dibenzyl, trans-1,2-dibenzoylethylene and 3,8-diamino-6-phenylphenanthridine, was investigated. The photoluminescence (PL) of green, yellow and red emitting light polymers and their blend was studied. These included the effects of excitation wavelength, concentration and film thickness on the PL. Photoluminescence properties of the PKs before and after protonation with 10-Camphorsulfonic acid (CSA) were tested. The structure formation of (PKs)(1)(CSA)(2) complexes are discussed on the basis of FTIR spectroscopy.

A series of 5 conjugated aromatic polyimines (Schiff-base polymers), containing -C=N- linkages in the backbone and various side-group substitutions, has been synthesized, characterized, and used to investigate the effects of molecular structure on the electronic structure and properties of these polymers. In this paper we report the photophysical behaviour of the Schiff-base polymers and their diluted solutions in DMA. The fluorescence excitation and emission spectra of these compounds were measured. These compounds show no evidence of excimer formation under these conditions and their fluorescence exhibits in solid state and in solution first-order decay behaviour.

New polyethers have been obtained in the anionic polymerization of oxiranes containing carbazole andlor hydrazone groups in the substituent. Excitation and luminescence spectra of the novel polymers were measured in powder and in tetrahydrofuran solution. It allowed to conclude that in the absence of excimer trapping sites, only intermolecular energy migration will be encouraged in dilute solutions of the polymers. Some polyethers and their solutions in tetrahydrofuran showed blue fluorescence. That would have an application to electroluminescent materials, such as electroluminescence polymer diodes.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Luminescence emission and excitation spectra of a number of natural spodumene crystals have been measured at temperatures down to 12K. Both Cr3+ and Mn2+ centers were identified: Mn2+ is shown to be mainly in Li-sites rather than Al-sites and gives rise to abroad emission centered at 600 nm. In most spodumenes Cr3+ R-line emission with phonon sideband is observed at temperatures below 100K. In green hiddenite crystals Cr3+ emission is dominant at room temperature where the R-lines are superimposed on a broad-band emission. Calculation of the crystal-field splitting of the Cr3+ energy levels has been carried out assuming a C2v pseudo-symmetry for the Al-sites. In the more Mn- rich crystals multiple R1 lines are seen at temperatures below about 40K which are possibly associated with adjacent point defects due to charge compensation effects.

Previously, a relatively large splitting of the 2Eg state of Cr3+ in grossular Ca3Al2[SiO4]3 has been reported [M. Czaja and Z. Mazurak, Opt. Mater 3 (1994) 95]. The absorption and luminescence spectra of crystals containing Cr3+ and V3+in grossular Ca3Al2(SiO4)3 garnets (variety tsavorite) have been studied for the first time. From these spectra measured at room and liquid helium temperatures we determined energies of R2, R1, and 4T2g levels of Cr3+. The lifetimes and splitting of the 2Eg state have been measured by tuning the excitation energy within the inhomogeneous profile of the R1 and R2 lines of the split 2Eg → 4A2g transition. To account for the thermal quenching of the R-lines, it is necessary to recognize that the two components of the doublet may have remarkably different radiative lifetimes (7500 and 2500 μs). These lifetimes were obtained from low temperature decay and from the temperature dependence of the intensity ratio of the R2, R1 components. These separate lifetimes as well as the lifetime of the 4T2g state were then set to fit the temperature dependence of the joint effective lifetime. The optical fluorescence of a V3+ dopant is characterized by the broad band infrared fluorescence spectrum associated with short decay time < 1μs.

The optical absorption and luminescence spectra of MgAl2O4:Cr3+ natural spinel (from Ural) have been measured at 77 K and 293 K. The luminescent emission from 4T2g, 2Eg covers wide region of 600–750 nm. The emission spectrum at 77 K shows a very rich vibrational structure which can be mainly explained through the vibrational modes of the oxygen octahedron.

Good quality uranium(3+) doped single crystals of Cs 2 NaYCl 6 have been obtained by the Bridgeman-Stockenberger method. The absorption, IR, Raman and luminescence spectra of the crystals were recorded and discussed. X-ray powder diffraction patterns of Cs 2 NaUCl 6 and Cs 2 NaUCl 6 :U 3+ were taken and the cubic lattice parameter determined.

The fluorescence spectra and lifetimes of low lying states of Er 3+ in Cs 2 NaErCl 6 single crystals have been investigated at room temperature and at 77 K. The assignments of the 4 F 9 2 - 4 I 15 2 and 4 I 11 2 - 4 I 15 2 phonon-assisted transitions have been proposed. The fluorescence lifetimes of low lying fluorescing levels have been estimated.