Difluoro-boron-triaza-anthracene: a laser dye in the blue region. Theoretical simulation of alternative difluoro-boron-diaza-aromatic systems

The synthesis, photophysical and laser properties of a difluoro-boron-triaza-anthracene (BTAA) compound are analyzed in the present paper. The molecular structure of this dye is an anthracene-like core with N atoms at 4a, 9 and 10a positions where two of them (4a and 10a) are linked through a BF(2)-bridge group. This structure is reminiscent of aza-BODIPY dye with an s-indacene core, BODIPY being one of the most commonly used laser dye family in the Vis region. The main absorption and emission bands of the new dye are localized in the blue part of the Vis region of the electromagnetic radiation, a spectral region practically unexploited by the BODIPY chromophore. Moreover, the new dye presents a higher laser efficiency and photostability than other commercial laser dyes operating in the same spectral region. In order to look for new molecular structures with potential laser emission covering the whole Vis spectral region, the spectroscopic properties of other different chromophoric systems based on BF(2)-linking aromatic groups are theoretically simulated by quantum mechanical calculations.     

Two-photon laser photochemistry of a coumarin laser dye

Irradiation of 7-dimethylamino-4-methylcoumarin (1), a commercially available laser dye, in ethanol solution with the focused output of an XeCl excimer laser at 308 nm resulted in the formation of yellow oligomeric material derived from the ethanol solvent. The efficiency of formation of the yellow material was shown to be dependent on the intensity of the laser light, indicating that the photochemistry involved absorption of two photons. The oligomeric material is proposed to be a substance which interferes with stimulated emission in coumarin dye lasers. In addition, acetaldehyde and several gaseous products, principally hydrogen and butane, were formed. A product resulting from the coupling of 1 with the ethanol solvent was also isolated and characterized. Excimer laser irradiation of 1 in methanol yielded formaldehyde, hydrogen and solvent oligomers, while irradiation of 1 in benzene resulted in the formation of a black precipitate. The non-oligomeric products are similar to those observed from the direct irradiation of the solvent in the vacuum-UV region. A mechanism is proposed for the observed photochemistry in which 1 absorbs, sequentially, two photons from the laser pulse, resulting in the formation of a highly excited state which then transfers energy to the solvent.     

A tunable picosecond dye laser for use in dioxin analysis.

A distributed-feedback dye laser with a quenching cavity was designed and constructed for generating a tunable picosecond pulse with a narrow spectral linewidth. This nearly transform-limited pulse was succeedingly amplified by a triple-pass off-axis amplifier. The pulse duration and the spectral linewidth were 60 ps and 9.4 pm, respectively. The amplified pulse was frequency-doubled by second-harmonic generation, producing a 0.5-mJ pulse with no background emission. The potential advantage of this laser in the analysis of dioxin based on supersonic jet/resonance-enhanced multiphoton ionization/mass spectrometry is discussed.     

Thermodynamics of surfactant-dye complex formation in aqueous solutions II. Sodium dodecyl sulfate and some azo oil dye systems

Spectrophotometric and thermodynamic investigations are reported of the interactions between anionic surfactant (sodium dodecyl sulfate) and six azo oil dyes (benzene azo naphthalene type) which have an amino group at 4-position of naphthalene. A pronounced spectral change in the dye solution occurs on addition of surfactant. For increasingly surfactant concentrations (below the CMC), the interaction between dye and surfactant is so sharp that the systems may be said to exhibit an isosbestic point; then a new absorption band appears at longer wavelengths. The spectral data can be quantitatively interpreted in terms of a complex formation. The equilibrium coefficients of the complex formation are determined at different temperatures. The thermodynamic parameters of the complex formations (the free energy change (G), enthalpy change (H) and change in entropy (S) are also calculated. The reaction of complex formation is exothermic (H negative).G is dependent on the hydrophobic nature andpKa of the dye. These complexes will form due to hydrophilic-hydrophilic interaction and will become more stable due to hydrophobic-hydrophobic interaction.With increasing amounts of complex, the infinite adsorption, the exhaustion and the rate constant of dyeing for nylon decrease.     

N2 laser pumped dye laser photolysis

An N₂ laser pumped dye laser has been used as the exciting pulse source in flash photolysis with a time resolution in the ns range. Using the apparatus described it was possible to monitor second order decays. Advantages of this set-up are tunability, reproducibility of the exciting source, and the rapidity of the measurements.     

Transient absorptions in a polymethine laser dye

Transient absorptions in HITC are investigated in the range 650-950 nm by a conventional flash photolysis technique and “picosecond” spectroscopy with a train of 6 to 7 pulses. This study gives evidence for S₁-S_n absorption, photoisomer and triplet generation. The comparison between experimental data and computer solutions allows the determination of the rate constants of these processes and molar extinction coefficients of the absorption spectra. Taking into account these results, we discuss the limitations of the performances of the flashlamp excited HITC dye laser.     

Hybrid materials for solid-state dye laser applications

The quest for a solid-state tunable dye laser can be satisfied by sol-gel prepared organic-inorganic hybrids. A photostability study of porous silica-Rhodamine 6G hybrids prepared via a sol-gel method is presented. The dye molecules can be incorporated into the silica matrix by forming weak or covalent bonds (hybrids of classes I and II, respectively). New class II samples and traditional class I materials prepared by the pre-doping method were synthesized. Samples were characterized by photoluminescence measurements to compare the emission properties and the photostability of the samples. The decay of the fluorescence signal as the cumulative excitation energy increases is reported and interpreted by hypothesizing that the dye molecules can be hosted in different surroundings within the porous glass matrix. The reported photoluminescence and photobleaching features indicate the class II samples as good candidates for solid-state dye lasers.     

Investigation of near-infrared laser dye albumin complexes

Near-infrared (NIR) spectroscopy is used to investigate the properties of the NIR laser dye albumin complexes. The binding sites on albumins are probed using four structurally very similar NIR laser dyes, the DTTCI, DOTCI, DTDCI and DODCI. The pronounced differences observed in the NIR spectra of these dyes indicate that specific binding may occur since differences in the microenvironment of the binding area does not alone explain these changes. The DTTCI complexes with albumins showed a significant decrease in the NIR absorption while the other three dyes did not. These results suggest that the presence of the S heteroatoms as well as their distance from each other are determining factors in the observed specific binding. Dissimilarities in the NIR spectra of different albumin complexes indicate a difference in the structure of the microenvironment surrounding the NIR laser dye binding sites.     

Comments on the energy transfer dye laser

Kinetic analysis of an energy transfer dye laser is presented. The laser gain function depends on the molecular parameters and on the concentrations of both the donor and acceptor. For the low signal limit the gain shows linear dependence on either the donor or the acceptor concentrations for a fixed donor-acceptor concentration ratio. This behavior has been confirmed experimentally.     

Energy transfer distributed feedback dye laser using Rhodamine B-Acid blue 7 dye mixture

The characteristics of energy transfer distributed feedback dye laser (ETDFDL) are studied both theoretically and experimentally in a mixture of Rhodamine B and Acid blue 7 dyes pumped by 532 nm Nd:YAG laser. The behaviour of donor and acceptor DFDL, the dependence of their pulse width and output power on pump power and donor-acceptor concentrations are studied. Experimentally, the tunability is achieved over the spectral range 565-680 nm using a prism dye cell arrangement. The output energy of DFDL is measured at the emission peaks of donor and acceptor for different pump powers and donor-acceptor concentrations. The output pulse of DFDL is found to be as narrow as 40-ps duration, which is nearly 100-fold shorter than the pump pulse. The pulse linewidth is of the order of 0.1 A.     

Photocurrents in simple polymer systems. II

Large photocurrents have been observed in films of some simple polymers (containing no π-orbitals), of which poly(vinyl fluoride) is a typical example. Not only are the currents large (up to 10^?5 A/cm²) but also they are capable of being excited by light in the visible wavelength region where absorption by the polymer is too low to be detectable. The results indicate that the effects are electronic, rather than ionic, in nature.     

Synthetic thermally reversible gel systems. II

The homopolymer and many of the copolymers of N-acrylylglycinamide yield thermally reversible gels in water. These systems are uniquely suitable for studying synthetic photographic gelatin substitutes and for understanding the mechanism of the gelation process. Polymerization of N-acrylylglycinamide has been studied under a variety of conditions. The homopolymer is aggregated in dilute aqueous solution and probably molecularly dispersed in 2M thiocyanate solution. At concentrations of several per cent, in water, thermally reversible gels are formed whose melting points rise with increasing concentration and increasing molecular weight. The heat of gelation crosslinking has been calculated to be ?8.8 kcal./mole of crosslinks. Introduction of small amounts of carboxyl groups into the polymer raises the melting points of the aqueous gels. The effect of various organic and inorganic reagents on gelation is presented. The ability to prepare copolymers which can be flocculated has been demonstrated as well as the usefulness of the monomer in certain types of photoresist systems. Copolymerization with acrylic acid and β-aminoethyl vinyl ether has been studied, and the r₁ and r₂ values for these systems have been calculated as well as Q and e values for N-acrylylglycinamide.     

HCO radical kinetics: Conjunction of laser photolysis and intracavity dye laser spectroscopy

HCO radical at a concentration of about 10¹⁴ cm^?3 is produced by monochromatic laser photolysis of H₂CO with a 0.6 mJ frequency-doubled, flashlamp-pumped dye laser pulse. Intracavity dye laser spectroscopy quantitatively monitors HCO absorbance near 614 nm as a function of delay time between photolysis and probing pulses. Rate constants for HCO + O₂ and HCO + NO are found to be 4.0 ± 0.8 × 10^?12 and 1.45 ± 0.2 × 10^?11 cm³ molecule^?1 sec^?1.     

New laser dye based on the 3-styryl analog of the BODIPY dye PM567

We report the synthesis, photophysical properties and evaluation of laser dye of a new BODIPY dye with a 3-styryl substituent, PMS, and with the rest of the substituents as in the commercial dye PM567. PMS shows an emission band at 584 nm in methanol, i.e. displaced ca. 50 nm to longer wavelengths with regard to the green-emission band of PM567, as well as a high-fluorescence quantum yield (0.82) and also a high-molar absorption coefficient (10⁵ M⁻¹ cm⁻¹) in the same solvent. The laser action of the new dye has been analyzed under transversal pumping at 532 nm, 5.5 mJ pulse⁻¹ and up to 10 Hz repetition rate, in both liquid phase and incorporated into solid polymeric matrices of methyl methacrylate copolymerized with crosslinking or fluorinated monomers. Lasing emission at 602–610 nm, with maximum efficiencies of 18%, were reached in these media. In solid-fluorinated matrices, good lasing photostabilities were established, with 30% of the initial laser output remaining after 100,000 pump pulses at 10 Hz.     

Dynamic purity determinations. II. Some additional systems

Menadione and phenacetin systems were each prepared with a series of concentrations of materials of varying similarity to the host. The data indicate that the measured impurity is dependent upon not only the concentration but also the nature of the impurity. The determination of the actual beginning of melting by nuclear magnetic resonance results in more precise purity measurements.

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Zusammenfassung Es wurden Menadion- und Phenacetinsysteme mit je einer Konzentrationsreihe von Zusatzstoffen, der Matrix in verschiedentlichem Ausmaß ähnlich, hergestellt. Die Ergebnisse zeigen an, daß die gemessene Verunreinigung nicht allein von ihrer Konzentration, sondern auch von ihrer Natur abhängig ist. Genauere Reinheitsmessungen erfolgen aus der Bestimmung des wahren Schmelzanfangs mittels kernmagnetischen Resonanzmessungen.

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The data are taken from a dissertation presented in partial fulfillment of the requirements for the Doctor of Philosophy degree.

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This work was supported in part by the U.S. National Science Foundation through Research Grant CHE 76-08765.     

Radiochromic dye dosimeter solutions as reference measurement systems

Solutions of leucocyanides of triphenylmethane dyes in organic solvents are designed as stable reference dosimeters for large radiation doses, with useful characteristics, both for steady-state and pulsed radiation fields. These radiochromic solutions may be used in conventional glass ampoules to cover the absorbed dose range 10²–10⁴kGy, when analyzed spectrophotometrically at visible wavelengths at the maxima of radiation-induced absorption bands. The radiation chemical yields of dye formation (G-values) and molar linear absorption coefficients (ϵ_m) of the dyes in several formulations, with and without dissolved polymer and weak oxidizing agents, are established. The most stable formulation before and after irradiation consists of new fuchsin cyanide in a mixture of dimethyl sulfoxide and triethyl phosphate containing small amounts of acetic acid, p-nitrobenzoic acid and polyvinyl butyral. The useful range of doses for this solution is 10²-4 x 10³ Gy when measured at 557 nm wavelength. The radiation chemical yield, G-value for dye production, is 3.35 x 10¹⁵ molec J^-1 (0.0055 μmol J^-1) and the value of ϵ_m at this wavelength is 1.32 x 10⁵ M^-1 cm^-1.     

Redox switchable NIR dye derived from ruthenium-dioxolene-porphyrin systems

Newly synthesised Ru(bp)2(sq)(+)-derivatives, covalently linked to a porphyrin-core, show very high epsilon values in the NIR region; which exhibit fast on/off switching depending on the redox state of the coordinated dioxolene functionality.     

Infrared laser heterodyne systems

This paper gives a review of mid-infrared laser heterodyne systems. The advantages of using heterodyne detection are described and the different techniques corresponding to the choice of the local oscillator are presented. A thorough discussion of the gas laser heterodyne systems is followed by the presentation of tunable diode laser systems capabilities. Many experiments in the mid-infrared region are reviewed covering the astronomical and atmospheric, ground-based and airborne investigations as well as the laboratory measurements.     

离子缔合物二级散射光谱的分析应用2: 汞(II)-硫氰酸盐-感性三芳基甲烷染料体系

研究了[Hg(SCN)4]^2^1与结晶紫、孔雀石绿、亮绿或碘绿等碱性三芳基甲烷染料的离子缔合配合物的二级散射(DS)和"反二级散射"(ADS)光谱, 以及这类散射光谱的特征、影响因素和反应的适宜条件。确定了散射光强度与溶液中汞(II)浓度的关系。提出了用二级散射光谱测定痕量汞的新的高灵敏分析方法, 并对反应机理和两种二级散射发生变化的原因作了初步的讨论。