Über die Photoleitung flüssiger Aromaten bei Anregung des Triplett-Zustandes

1966 ◽  
Vol 21 (4) ◽  
pp. 441-446
Author(s):  
H. Bässler ◽  
B. Dries
Keyword(s):  
Absorption Band ◽  
Light Intensity ◽  
Aromatic Compounds ◽  
Liquid State ◽  
Response Curve ◽  
Spectral Response ◽  
Dark Conductivity ◽  
Triplet Exciton ◽  
Intersystem Crossing ◽  
Absorption Region

Irradiation of the aromatic compounds Benzene, Naphthalene, Biphenyl, Pyrene, and Benzophenone in the liquid state with a Xenon-arc-lamp produces a photocurrent, if an external d. c. voltage is applied. This current is independent of the dark-conductivity and increases linearily with light-intensity. It does not appear, if blocking quartz electrodes are used. The spectral response curve shows one peak at the wavelength of the forbidden singlet-triplet absorption-band of the compound and another at the longwave-edge of the singlet-absorption-region. A model is proposed basing on the idea of triplet-exciton formation (T1) by direct S0—T1 transitions and by transitions from S1 to T1 states (intersystem-crossing). The triplet exciton can migrate to the electrodes and dissociate there for energetic reasons. The released electron is received by the electrode. The cation remains either in the liquid or recombines with the electron. The cation can contribute to the photocurrent only when the dissociation has happened at the anode. In agreement with the measurements, dissociation requires conducting electrodes and follows monomolecular kinetics.

Löschung der Perylen-Fluoreszenz durch Ag+ -Ionen / Quenching of the Perylene Fluorescence by Ag+-Ions

1983 ◽  
Vol 38 (6) ◽  
pp. 698-700 ◽  
Author(s):  
H. Dreeskamp ◽  
A. Läufer ◽  
M. Zander
Keyword(s):  
Triplet State ◽  
Dynamic Process ◽  
Aromatic Compounds ◽  
Heavy Atom ◽  
Silver Ions ◽  
Intersystem Crossing ◽  
Fluid Solution ◽  
Long Wavelength ◽  
Wavelength Emission ◽  
Atom Effect

The fluorescence of perylene in fluid solution (λ0.0 = 440 nm) is quenched by silver ions in a dynamic process according to a Stern-Volmer kinetics (kq = 2 · 109 [1 • mol-1 · sec-1], in ethanol at 295 K). Simultaneously an unstructured long-wavelength emission (λmax ≈ 470 nm) appears which we assign to a perylene/Ag+ exciplex. A similar emission is observed when other polvcyclic aromatic compounds (PAC) are used, whose fluorescence as in the case of perylene is not easily quenched in an external heavy atom effect by iodopropane (kq ≦ 106). In these cases the excited PAC/Ag+ complex is long-lived enough to emit fluorescence since the intersystem crossing to the triplet system is slow due to the absence of an energetically favorable accepting triplet state

Spectral properties of the tubuloglomerular feedback system

1997 ◽  
Vol 273 (4) ◽  
pp. F635-F649 ◽  
Author(s):  
H. E. Layton ◽  
E. Bruce Pitman ◽  
Leon C. Moore
Keyword(s):  
Transit Time ◽  
Spectral Properties ◽  
Response Curve ◽  
Feedback Loop ◽  
Spectral Response ◽  
Power Spectra ◽  
Tubuloglomerular Feedback ◽  
Feedback Gain ◽  
Thick Ascending Limb ◽  
Closed Feedback Loop

A simple mathematical model was used to investigate the spectral properties of the tubuloglomerular feedback (TGF) system. A perturbation, consisting of small-amplitude broad-band forcing, was applied to simulated thick ascending limb (TAL) flow, and the resulting spectral response of the TGF pathway was assessed by computing a power spectrum from resulting TGF-regulated TAL flow. Power spectra were computed for both open- and closed-feedback-loop cases. Open-feedback-loop power spectra are consistent with a mathematical analysis that predicts a nodal pattern in TAL frequency response, with nodes corresponding to frequencies where oscillatory flow has a TAL transit time that equals the steady-state fluid transit time. Closed-feedback-loop spectra are dominated by the open-loop spectral response, provided that γ, the magnitude of feedback gain, is less than the critical value γc required for emergence of a sustained TGF-mediated oscillation. For γ exceeding γc, closed-loop spectra have peaks corresponding to the fundamental frequency of the TGF-mediated oscillation and its harmonics. The harmonics, expressed in a nonsinusoidal waveform for tubular flow, are introduced by nonlinear elements of the TGF pathway, notably TAL transit time and the TGF response curve. The effect of transit time on the flow waveform leads to crests that are broader than troughs and to an asymmetry in the magnitudes of increasing and decreasing slopes. For feedback gain magnitude that is sufficiently large, the TGF response curve tends to give a square waveshape to the waveform. Published waveforms and power spectra of in vivo TGF oscillations have features consistent with the predictions of this analysis.

Spectral Response and Diagnostics of Biological Activity of Hydroxyl-Containing Aromatic Compounds

2016 ◽  
Vol 59 (4) ◽  
pp. 544-551 ◽  
Author(s):  
G. B. Tolstorozhev ◽  
G. V. Mayer ◽  
M. V. Bel’kov ◽  
O. I. Shadyro
Keyword(s):  
Biological Activity ◽  
Aromatic Compounds ◽  
Spectral Response

Cool flames in the combustion of toluene and ethylbenzene

1956 ◽  
Vol 238 (1213) ◽  
pp. 143-153 ◽  
Keyword(s):  
Hydrogen Peroxide ◽  
Light Intensity ◽  
Benzoic Acid ◽  
Aromatic Compounds ◽  
Flow System ◽  
Reaction Vessel ◽  
Static System ◽  
Cool Flame ◽  
Cool Flames ◽  
Blue Flame

The oxidation of toluene and ethylbenzene has been studied in a static system using a spherical reaction vessel (700 ml.) over the temperature range 300 to 500°C, and at total pressures up to 600 mm. Cool flames were observed in the oxidation of both hydrocarbons, but only the reaction of ethylbenzene gave rise to a ‘blue’ flame at higher temperatures. With neither hydrocarbon did periodicity in light intensity, or pressure pulses, occur. The ignition diagrams for 4 to 1 fuel + oxygen mixtures have been mapped out. With ethyl­benzene, the cool flame was maintained in a flow system, its spectrum was photographed and shown to be similar to that of fluorescent formaldehyde. The products of the reaction con­tained acetophenone, benzaldehyde and benzoic acid, phenol, quinol, hydrogen peroxide and methoxyhydroperoxide. The results have been compared with corresponding data for the oxidation of paraffin hydrocarbons, and it is concluded that, with both aromatic compounds, the processes allowing the possibility of cool-flame formation are themselves secondary in nature.

Notizen: On the Relationship Between the Rates of the Radiative and Radiationless Deactivation of the Lowest Triplet State of Aromatic Compounds

1988 ◽  
Vol 43 (4) ◽  
pp. 393-394 ◽  
Author(s):  
Maximilian Zander
Keyword(s):  
Triplet State ◽  
Rate Constants ◽  
Aromatic Compounds ◽  
Energy Gap ◽  
Intersystem Crossing ◽  
The Relationship ◽  
Linear Correlations

Abstract For groups of structurally related aromatic compounds with similar T1 - S0 energy gap linear correlations exist be­ tween the rate constants of the radiative and radiationless T1 → S0 transition. Significant exceptions may indicate further radiationless deactivation processes originating in T1 in addition to T1 → S0 intersystem crossing.

scholarly journals The chemistry of flavines and flavoproteins. Photoreduction of flavines by amino acids

1968 ◽  
Vol 109 (2) ◽  
pp. 259-268 ◽  
Author(s):  
G. R. Penzer ◽  
G. K. Radda
Keyword(s):  
Carbon Dioxide ◽  
Amino Acids ◽  
Light Intensity ◽  
Potassium Iodide ◽  
Aromatic Compounds ◽  
Phenylacetic Acid ◽  
Intramolecular Interaction ◽  
Kinetic Scheme ◽  
Dimethyl Sulphoxide ◽  
Triplet States

1. Flavines are photoreduced through their triplet states by amines and amino acids (e.g. EDTA and dl-phenylglycine). The anaerobic photoreduction of FMN and several other flavines with dl-phenylglycine was analysed in terms of a detailed kinetic scheme. 2. The reaction produces equimolar amounts of benzaldehyde, carbon dioxide and reduced flavine. 3. The sensitivity of the rates to substituents in the dl-phenylglycine can be described by a Hammett ρ-value of −1·1. 4. Phenylacetic acid behaves differently from dl-phenylglycine or benzylamine towards a series of flavines. 5. The photoreductions are quenched by several aromatic compounds. From the effects of light-intensity and temperature, and by comparison with potassium iodide quenching, it is concluded that inhibition by the aromatic compounds is not simply a collisional process. 6. FAD reacts more slowly than FMN both in the photoreduction and in dark reduction by NADH. Urea and dimethyl sulphoxide decrease the intramolecular interaction in FAD, but they have no effect on the rate of dark reduction of FAD compared with FMN. In contrast, the photoreduction of FAD is quicker in urea.

PHOTOINDUCED PHASE TRANSITION IN SINGLE CRYSTALS ON URETHANE-SUSTITUTED POLYDIACETYLENES

2001 ◽  
Vol 15 (28n30) ◽  
pp. 3969-3972 ◽  
Author(s):  
Hiroaki Tachibana ◽  
Noriko Hosaka ◽  
Masayuki Osaki ◽  
Yoshinori Tokura
Keyword(s):  
Phase Transition ◽  
Absorption Band ◽  
Light Intensity ◽  
Single Crystals ◽  
Photon Energy ◽  
Room Temperature ◽  
Photogenerated Electron ◽  
Reflectance Spectra ◽  
Electron Hole

Thermochromic behaviors were investigated by measurements of reflectance spectra for urethane-substituted polydiacetylene crystal having side groups of R=(CH)2)6OCONHC2H5 (PDA-6UEt). The PDA-6UEt crystal shows an irreversible thermochromic A-to-B (blue-to-red) phase transition: the absorption band at 1.88 eV due to the lowest exciton shifts to higher energy (2.15 eV) in the heating run, but the reflectance spectra remain in the B phase even when cooled down to room temperature. We have demonstrated that photoinduced phase transition (PIPT) is observed by utilizing the irreversible A-to-B phase transition. The conversion shows the presence of a threshold of the light intensity and depends on photon energy, suggesting that the PIPT is mediated by the photogenerated electron-hole pairs.

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