Transient absorption in fused silica induced by trains of high-energy electron pulses

This Letter describes some preliminary experiments in which fused silica (Suprasil II) is irradiated by trains of high-energy electron pulses and the subsequent transient absorption is recorded. Absorption bands with varying decay kinetics were observed, indicating that various lattice defects or color centers were formed.     

Highly sensitive detection of optical discrete absorption and resonance fluorescence of fused silica in the far ultraviolet

Ultraviolet light induced high resolution optical absorption spectra and resonance fluorescence of spectroscopically pure fused silica have been studied, due to its potential applications in optoelectronics and flash (laser flash spectroscopy laboratory use), for optical fibers and power optics and lasers. An ultraviolet discrete absorption spectra and resonance coherent fluorescence were recorded photographically between 200 and 260 nm. Resonance discrete and coherent fluorescence were observed at 250-255 and 220-225 nm bands at room temperature by flash photolysis technique.     

Study of light-scattering changes induced in tRNA solutions by a strong optical field of picosecond pulses

Changes in the light-scattering components (λ = 0.53 μm) induced by a strong picosecond optical field (λ = 1.06 μm) applied to macromolecular transfer ribonucleic acid (tRNA) solutions were studied. Two beams were polarized vertically, and the intensity of the vertical and horizontal components of the light (λ = 0.53 μm) scattered at an angle of 90° were measured. The electric field of the strong 30-ps laser pulse was 5.0 × 10³ esu cgs. The experimentally determined changes allowed for calculation of the mean third-order optical polarizability c, and its anisotropy δ_c. The measurements were performed in three different solutions: salt free, with magnesium ions, and without magnesium ions. Changes in tRNA structure reflected in changes of nonlinear light scattering, third-order optical polarizability, and its anisotropy were observed.     

Flow cell within an LED: a proposal for an optical absorption detector

Droplets formed at the tip of a tube under the same conditions possess extreme uniformity of form, volume and weight. These properties of liquid drop formation have been known for a long time and consequently many applications for the drop have been found in instrumentation and chemical analysis methods. In the present paper, we report on the analytical use of a dynamic LED-based flow-through optical absorption detector with optical path length controlled by continuous dropping of a solution. This arrangement consists of a flow cell built within a high-intensity red LED (λ _max = 630 nm). The feasibility of the detector is demonstrated by colorimetric determination of methylene blue, and ammonium by Berthelot’s reaction, in a flow-injection system. For ammonium, the reaction forms a blue dye (indophenol) with a maximum absorption at 630–650 nm. The detection limit, considered as 3 times the signal of the blank, is better than 125 μg l^-1. The small flow cell represents a good combination of optical path length, low volume and fast washout. This detector can be used advantageously in automated methods and can represent a solution to problems of optical detection involving gas bubbles and precipitation of particles in turbidimetric applications.     

On the windows in the absorption spectrum of an ensemble of oscillators embedding an impurity oscillator

The windows in the absorption spectrum of a harmonic oscillator coupled to a bath can be given a two-parameter form identical to the Fano windows in the absorption cross section of an atom with an autoionizing state.     

Time-resolved optical absorption of an exciplex in a doped polymer film

The excited-state absorption spectrum and deactivation mechanisms of an exciplex state formed between N-isopropylcarbazole (NIPC) and dimethylterephthalate (DMT) in doped PMMA films are observed by applying laser photolysis techniques. The results are discussed in comparison to measurements of a similar system in a non-polar solution.     

Transient absorption spectra of pinacyanol and cyanine photoisomers obtained with a sync-pumped picosecond dye laser and independently tunable probe light

We have measured the absorption difference spectra and quantum yields of photoisomers of pinacyanol iodide and 1,1′-diethyl-4,4′-cyanine iodide on a picosecond time scale using syne-pumped picosecond dye laser pulses for excitation and independently tunable analyzing light.     

Nature of the optical absorption spectra of the trapped electron in irradiated frozen water solutions

Conclusions The optical absorption spectra of the trapped electron were measured in irradiated glasslike solutions of NaOH, KOH, and NaClO₄ in H₂O and D₂O at — 196°. The same as at room temperature, the spectra are caused by a transfer of the charge to the solvent.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 1637–1639, September, 1966.     

Some improvements in the determination of volatile nitrosamines by fused silica capillary-GC in combination with a thermal energy analyzer

Summary Fused silica capillary columns of different diameters and polarities are linked to a thermal energy analyzer and a flame ionisation detector for comparison. Extra column effects are discussed. Unsymmetrical homologue nitrosamines are applied in order to assign the volatile nitrosamines most often to be determined by their linear indices rather than by their overall retention times.     

One-step immobilization of glucose oxidase in a silica matrix on a Pt electrode by an electrochemically induced sol-gel process

We demonstrate here that the electrochemical generation of hydroxyl ions and hydrogen bubbles can be used to induce the synthesis of enzyme- or protein-encapsulated 3D porous silica structure on the surface of noble metal electrodes. In the present work, the one-step synthesis of a glucose oxidase (GOD)-encapsulated silica matrix on a platinum electrode is presented. In this process, glucose oxidase was mixed with ethanol and TEOS to form a doped precursory sol solution. The electrochemically generated hydrogen bubbles at negative potentials assisted the formation of the porous structure of a GOD-encapsulated silica gel, and then the one-step immobilization of enzyme into the silica matrix was achieved. Scanning electron microscopy (SEM) and scanning electrochemical microscopy (SECM) characterizations showed that the GOD-encapsulated silica matrix adhered to the electrode surface effectively and had an interconnected porous structure. Because the pores started at the electrode surface, their sizes increased gradually along the distance away from the electrode and reached maximum at the solution side, and effective mass transport to the electrode surface could be achieved. The entrapped enzyme in the silica matrix retained its activity. The present glucose biosensor had a short response time of 2 s and showed a linear response to glucose from 0 to 10 mM with a correlation coefficient of 0.9932. The detection limit was estimated to be 0.01 mM at a signal-to-noise ratio of 3. The apparent Michaelis-Menten constant (K m app) and the maximum current density were determined to be 20.3 mM and 112.4 microA cm-2, respectively. The present method offers a facile way to fabricate biosensors and bioelectronic devices in situ.     

Micropatterning of biomolecules on a glass substrate in fused silica microchannels by using photolabile linker-based surface activation

Platinum nanoparticles were electrodeposited onto a film of dihexadecyl hydrogen phosphate deposited on a glassy carbon electrode (GCE) and modified with dispersed acetylene black. Scanning electron microscopy and electrochemical impedance spectroscopy revealed that this nanocomposite has a uniform nanostructure and a large surface area that enables fast electron-transfer kinetics. The modified GCE showed high electrocatalytic activity for the oxidation of nitric oxide (NO). Under optimal conditions, the oxidation peak current of nitric oxide is linearly related to the concentration of NO in the concentration range between 0.18 and 120?μM, and the detection limit is as low as 50?nM (at an S/N of 3). The modified electrode was successfully applied to sensing of NO as released from rat liver.

Synthesis of a chlorophyll-a derivative fused with an additional exo-five-membered ring and its optical properties

A C20-free chlorophyll-a derivative with an additional exo-five-membered ring was successfully prepared using an ethylene linkage at the C3- and C5-positions. A bromination at the C20-position was requisite for the cyclization of a 1-hydroxyethyl or vinyl group at the C3-position of methyl bacteriopheophorbide-d or methyl pyropheophorbide-a, respectively. By comparing optical properties of the cyclized product with those of its 3-ethyl uncyclized analog in a diluted dichloromethane solution, it was shown that the cyclization shifted the Q_x and B_x absorption maxima to longer wavelengths and reduced the Stokes shift.     

Dynamics of the isomerization of trans-stilbene in n-alcohols studied by ultraviolet picosecond absorption recovery

We have used a simple At⁺ synchronously pumped and cavity-dumped dye-laser system to generate UV picosecond pulses with energies sufficiently high for absorption recovery experiments. With these pulses, we have studied the dynamics of the isomerization of trans-stilbene in n-alcohols as a function of viscosity and temperature. It is concluded that the excited-state barrier of trans-stilbene in n-alcohols is less than 1 kcal mol^?1 and that the trans → cis isomerization yield is 0-54 ± 0.05.     

Determination of silica in geological materials by atomic absorption spectrometry

A simple rapid method for the routine determination of silica by atomic absorption spectrometry (a.a.s.) in a wide range of geological materials is described. Samples are decomposed by heating with hydrofluoric acid in closed containers and diluted gravimetrically. Large concentrations of free hydrofluoric acid are tolerated and the resulting solutions show excellent stability. No chemical interference was identified in the atomic absorption measurements. The technique was extended to the micro-determination of silica in samples of milligram size as well as trace-level silicon in waters. The average standard deviation is ?1% by the recommended method, 2.6% by the micro-method and 2–6% at trace level (20–0.5 ppm Si), respectively. The procedure described complements the a.a.s. scheme in current use for some 25 major and trace elements.     

Fast self-propagating chemical processes in inorganic solids induced by an elastic wave pulse

Fast self-propagating chemical processes in solids initiated by an elastic wave pulse were studied in relation to ammonium dichromate. A possible mechanism for these processes was proposed. Dedicated to the memory of Academician M. E. Vol'pin timed to his 75th birthday. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1140–1144, June, 1998.     

The application of an absorption cell for determining of some metals by atomic absorption

Summary The fish-tail burner, frequently used in atomic-absorption spectroscopy, is replaced by a specially constructed glass absorption cell. Such a cell provides a longer absorption path, thus considerably enhancing the sensitivity (10- to 50-fold). Atomic absorption measurements of iron, cobalt, copper, silver and lead have been carried out. The best concentration range for measurements was found to be between 0.1g/ml and 1g/ml and in some cases even lower. Reproducibility was good. The influence of 15 common elements in various concentrations has been investigated for all five elements measured, and the results are discussed. Trace elements have been separated from large quantities of other elements of a sample by extraction, and the method used for their determination in nuclear grade uranium, water samples, plants, and soil extracts. The results were accurate and reproducible, and the method convenient because of its high sensitivity, simplicity and rapidity.

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Zusammenfassung Der bei der Atomabsorptions-Spektroskopie meist benützte Schmetterlingsbrenner wurde durch eine speziell konstruierte Absorptionszelle aus Glas ersetzt. Diese bietet einen längeren Absorptionsweg und führt damit zu einer beträchtlichen (10- bis 50fachen) Steigerung der Empfindlichkeit. Atom-absorptionsmessungen von Eisen, Kobalt, Kupfer, Silber und Blei wurden durchgeführt. Das beste Konzentrationsbereich für diese Messungen liegt zwischen 0,1 und 1g/ml, in manchen Fällen noch darunter. Die Reproduzierbarkeit war gut. Der Einfluß von 15 üblichen Elementen in verschiedenen Konzentrationen gegenüber den fünf erwähnten Elementen wurde geprüft und die Ergebnisse diskutiert. Spurenelemente wurden von großen Mengen anderer Elemente in einer Probe durch Extraktion abgetrennt und das Verfahren für ihre Bestimmung in Uran für Kernspaltung, in Wasserproben, in Pflanzen und Bodenextrakten angewendet. Die Ergebnisse waren genau und reproduzierbar, das Verfahren wegen seiner hohen Empfindlichkeit, Einfachheit und Schnelligkeit gut geeignet.

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Résumé On a remplacé le brûleur en éventail fréquemment utilisé en spectroscopie d'absorption atomique, par une cellule pour absorption en verre construite spécialement. Une cellule de ce genre donne un trajet d'absorption plus long, et augmente donc considérablement la sensibilité (10 à 50 fois). On a effectué des mesures d'absorption atomique avec le fer, le cobalt, le cuivre, l'argent et le plomb. On a trouvé que le meilleur domaine de concentration pour les mesures se situait entre 0,1g/ml et 1g/ml et même moins dans certains cas. La reproductibilité a été bonne. On a suivi l'influence de 15 éléments usuels sous différentes concentrations pour les cinq éléments soumis à la mesure, en discutant les résultats. On a séparé par extraction les éléments à l'état de trace des autres éléments présents en grande quantité dans l'échantillon et on a utilisé cette méthode pour les doser dans des échantillons d'uranium de qualité nucléaire, dans l'eau, dans des plantes et des extraits de sols. Les résultats ont été très précis et reproductibles. La méthode s'est montrée commode en raison de sa haute sensibilité, de sa simplicité et de sa rapidité.

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This paper was presented at the Symposium on Analytical Chemistry held in Graz, 29th September–1st October 1965.