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The light excitation of P-960 results in the oxidation of P-960 and the reduction of P-800 (bacteriophytin b-800) in the reaction centers from Rhodopseudomonas viridis. A negative 847 nm band of the circular dichroism spectrum disappears under P-960 photooxidation, while a positive 827 nm band disappears under P-800 photoreduction. Exciton interaction of the pigment molecules in the reaction center is discussed.

Related to the sulphur annealing conditions, two different EPR signals are observed in CuGaSg2 With liquid sulphur, an isotropic photosensitive line is observed at g = 2.024 ± 0.002. With gaseous sulphur, an anisotropic spectrum, independent of light excitation, is recorded with g∥[001] = 2.114 ± 0.005 and g ⊥ [001] = 2.005 ± 0.005. The suggested models for the intrinsic centres correspond respectively to a hole trapped on a copper vacancy and to a S molecule ion. The formation of both centres, important for the electrical compensation processes in CuGaS, is justified by the molecular composition of sulphur as a function of its physical state. Deux signaux RPE sont observe;s sur CuGaS2 en fonction des conditions de recuit en pre;sence de soufre. Dans le soufre liquide, un signal photostimulable et isotrope apparait avee g = 2,024 ± 0,002. Dans le soufre gazeux, un spectre anisotrope et non photostimu-lable, est observe; avec g∥[001] = 2,114 ± 0,005 et g⊥[001] = 2,005 ± 0,005. Les modeles sugge;re;s pour ces de;fauts intrinse;ques correspondent respectivement a un trou pie;ge;: sur une vacance de cuivre et a un ion moleculaire S. La formation de ces deux centres, importante pour les processes de compensation electrique de CuGaS2, est justifyee par la composition moleculaire du soufre en fonction de son etat physique.

Light excitation of Gd3+ in fluoroarsenate and fluorophosphate glasses to the 6Ij and 6DJ multiplets leads to luminescence, originating from the 6P72 and 6P52 levels, with an evolution time dependent on the nature of the glass (1.3−1.4 ms and 1.1−1.2 ms respectively) and a lifetime (9.2 ms) independent of the host lattice. The luminescence rise time, which relates to the relaxation time of the 6IJ and 6DJ multiplets, leads to values of k1 + kr for the 6IJ multiplet equal to 2.7 × 103s−1 (fluoroarsenate) and 3.9 × 103s−1 (fluorophosphate). Slightly shorter luminescence rise times were observed following excitation of Gd3+ to the 6DJ multiplet. Direct excitation of Gd3+ to the 6PJ levels leads to luminescence with no measurable rise time and with a lifetime equal to 9.2 ms.

A photogalvanic cell composed of two half cells of the type [Rb-THF] I and [Rb-THF, crown ether (or kryptand)] II is reported. Photocurrents and photovoltages, recorded at low temperatures, in the order of 6 nA and 80 mV, respectively are obtained with light excitation at wavelenghts above 640 nm. The corresponding values with excitation above 320 nm, are 30 nA and 250 mV, respectively.

Recombination luminescence (π and σ) in KI has been observed with red light stimulation after or during exposure at 78 K to UV light. Using a pulse annealing technique, the hopping migration of V K centers is studied by monitoring the decrease of the photostimulated luminescence as a function of time and temperature. It is confirmed that the long-range diffusion of V K centers is characterized by a thermal activation energy of 0.27 eV. When a preexposed sample is warmed to 124 K, subsequent red irradiation at 78 K is found to stimulate the E x (3.02 eV) emission in place of the π emission. This can be regarded as evidence in favor of the extrinsic nature of the E x emission. Thermal quenching of the E x , π and σ emissions is also investigated in detail under UV light excitation. On the basis of these results, we discuss the nonradiative decay process of the self-trapped excitons in KI.

Light-induced formation of the 410 nm intermediate was investigated with reconstituted bacteriorhodopsin. Only bacteriorhodopsin with all-trans retinal formed the 410 nm intermediate in response to light excitation. In equilibrium in the dark, both native and reconstituted bacteriorhodopsin contained about equal amounts of the all-trans and 13-cis forms over a wide range of temperature.

The correlation between the excitation and fluorescence polarizations of the 4T2 → 4A2 broadband luminescence is investigated. The behaviour of the emission with the wavelength is also studied when modulating the light excitation either in intensity or in polarization. The results can be explained assuming that the broadband arise from different relaxed levels.

The influence of light excitation on the anodic oxidation of a silver electrode in alkaline solutions has been studied. The experimental results have shown that, in addition to the formation of Ag(II) species by a reaction of Ag(I) species with photo-generated holes, illumination in the Ag2O formation region causes the photogeneration of Ag(I) species at the metal/oxide interface. In the presence of ethylene glycol, the so-called current doubling phenomenon was found. This phenomenon has been interpreted in terms of a mechanism involving a catalytic reaction of the glycol with the photogenerated Ag(II) species, and not by a mechanism involving the oxidation of glycol by the photo-generated holes.

— A streak camera detection technique has been used to record the fluorescence of bacteriorhodopsin at room temperature induced by single subpicosecond light pulses. The fluorescence lifetime of bacteriorhodopsin has been found to be less than 2 ps.

It is shown that, if one uses an essentially monochromatic but weakly modulated light source to excite atoms or molecules in a resonant way, the phase shift of the scattered light is strongly dependent on the strength of the excitation. However, for low values of the excitation strength, this dependence disappears but a result which differs by a factor of two from the result obtained for broad-band light excitation is found. In addition, the strength of the modulated component of the scattered light displays a resonant behaviour in the modulation frequency, this response being directly related to the well-known Autler-Townes effect.

The relative increase in the decay of delayed light emission from photosynthetic membranes following far-red light excitation is shown to be related to thermoluminescence peak V appearing at 321 K. Peak V and the relative increase in the decay of delayed light emission show parallel changes in their intensities following far-red excitation.

It is possible to change the ionization state of iron in ZnS by light excitation in the visible and uv and by changing sample temperature. This can be confirmed by ESR-measurements. To clarify the nature of a new emission band (λmax = 980 nm) in ZnS: Fe a comparison between luminescence- and ESR-measurements has been performed. These results can be interpreted by assuming Fe3+ -ions as the emitting centers for the 980 nm luminescence. Furthermore a sensitization of this emission by the self-activated luminescence is concluded.

By studying the response of a two-level system to a narrow-band light excitation completely modulated in amplitude, a new manifestation of the dynamical Stark effect is predicted. It can be observed not only through the modulation rate or the phaseshift of the scattered light but also through the mean total intensity. Thus its experimental observation should be particularly easy.

At very low temperature, the reflection properties of CuCl samples under high pulsed light excitation conditions are investigated by a “pump and probe” technique. The non-linear reflection changes are shown to have different origins and different time scales: excitonic effects lead to a new reflection structure near the energy of the longitudinal exciton (∼ 1 ns time scale) and interaction with non-thermalized acoustical phonons to a decrease of the exciton reflection maximum (∼ 60 ns). Nous etudions, a tres basse temperature, par une technique de “sonde et de pompe” la reflexion d'echantillons de CuCl, places dans des conditions d'excitation intense par une source lumineuse puisee. Les changements non-lineaires de reflexion observes ont differentes origines et differentes durees: des effets excitoniques entraǐnant l'apparition d'une nouvelle structure de reflexion pres de l'energie de l'exciton longitudinal (d'une duree de l'ordre de la nanoseconde) une interaction avec des phonons acoustiques non-thermalises entraǐnant la diminution du maximum de reflexion (duree d'environ 60 ns).

The process of light- and dark-adaptation of bacteriorhodopsin was studied by measuring the photoelectric response signal corresponding to the M form of the light-adapted photocycle. Two different kinds of sample were used: oriented dried samples and oriented gel samples. It was shown that the quantum efficiency of light-adaptation does not depend on the temperature of the sample, but strongly depends upon the water content, which means that in this process the determining step of the branching is the light excitation (bacteriorhodopsin to bacteriorhodopsin ∗ or bacteriorhodopsin ∗ to the next state), not a later step during the 13-cis photocycle. The process of dark-adaptation depends upon both the temperature and the humidity of the sample.

Delayed luminescence was measured from samples of a synchronously growing cell culture of the unicellular green alga, Scenedesmus obtusiusculus Chod., every second hour during the 24 h cell cycle under a 15/9 h lighi/dark regime. Both high (air + 2.5% CO2) and low (0.03% CO2) CO2 conditions were used. Under high CO2 conditions, while light excitation induces formation of a late (maximum reached after 10–60 s) transient peak in delayed luminescence in cells sampled after 10–16 h in the cell cycle. During most of the cell cycle low CO2 conditions stimulate a late transient peak formation. Excitation with 700 nm light, but not with 680 nm light, induces a late transient peak in delayed luminescence under high CO2 conditions. The transient peak is more or less pronounced depending on the cell stage. The variations might be due to a changing capacity for light-induced state I/stale II transitions during the cell cycle. It is assumed that the formation of a late transient peak in delayed luminescence is due to ATP hydrolyzation and is thus favoured by a high ATP/NADPH ratio. Hydrolyzation of ATP affects the transthylakoidal ΔpH, which regulates the reverse electron flow to the plastoquinone-pool and QA/QB, thus affecting the decay kinetics of the delayed luminescence.

Lifetime measurements are performed on KCl:SrCl2 and KCl: CaCl2 by light excitation in the spectral region of the Z4-center absorption band. The main results are as follows: i) confirmation of Briginets' discovery, in KCl:SrCl2, of an MA-type center (i.e. an M-center perturbed by a foreign positive ion), whose absorption band strongly overlaps the Z4-center one; ii) evidence of an analogous MA-type center also in KCl:CaCl2; iii) explanation of the puzzling results on the Z4-center luminescence, obtained by Nishimaki, who found two emission bands for this center, in KCl doped with Ca, Sr, Ba; iv) assignment of the highest energy Nishimaki emission band to the MA-type center and not to the Z4-center. An analysis of the lifetime values for the unperturbed and for the perturbed M-center in KCl, taking into account the data previously obtained by the authors for the MA-center in KCl:NaCl and KCl:LiCl, shows their dependence on a relaxation parameter. A critical examination of the matter is also given: in particular, no contradiction is found with Briginets' hypothesis of a similarity between the Z4-center and the N1-center in undoped KCl crystals, although this analogy cannot be proved by measurements presented here. Messungen der Lebensdauer von Farbzentren werden an KCl:SrCl2 und KCl:CaCl2 bei optischer Anregung im spektralen Absorptionsbereich des Z4-Zentrums ausgefuhrt. Die wichtigsten Ergebnisse sind die folgenden: i) Bestatigung der Entdeckung von Briginets bezuglich eines Zentrums vom Typ eines MA-Zentrums (d. h. eines Zentrums, das von einem andersartigen positiven Ion gestort wird) in KCl:SrCl2, dessen Absorptionsbande stark diejenige des Z4-Zentrums uberlagert ii) Evidenz eines ahnlichen Zentrums vom Typ MA auch in KCl:CaCl2; iii) Erklarung der Ergebnisse von Nishimaki, der in der Lumineszenz des Z4-Zentrums in KCl, das mit Ca, Sr, Ba dotiert ist, zwei Emissionsbanden findet; iv) Zuordnung der hochsten Energie der Nishimaki-Emissionsbande zum MA-Zentrum anstatt zum Z4-Zentrum. Eine Analyse der Ergebnisse fur die Lebensdauer des gestorten und nicht-gestorten M-Zentrums in KCl unter Berucksichtigung einiger vorhergehender Messungen der Autoren am MA-Zentrum in KCl:NaCl und KCl:LiCl zeigt ihre Abhangigkeit von einem Relaxationsparameter. Es wird eine kritische Sicht des gesamten Problems durchgefuhrt: unter anderem wird kein Widerspruch gefunden mit Briginets Hypothese bezuglich einer Ahnlichkeit zwischen dem Z4-Zentrum und dem N1-Zentrum in nicht-dotierten KCl-Kristallen, obwohl diese Analogie nicht durch die hier wiedergegebenen Messungen bewiesen werden kann.

Asymmetric spectral shape of the 5D0−7F0 transition as well as anomalous emission spectra under monochromatic light excitation in Ca(PO3)2: Eu3+ are explained by taking account of broad distribution of crystal field acting on Eu3+. Energy level scheme of Eu3+ in this system and Eu3+−Eu3+ energy transfer mechanism are discussed.

The blue and red fluorescence of cryptocyanine solutions was observed under conditions of steady-stay light excitation and during Q-switched ruby laser excitation. Experimental results give evidence that the blue fluorescence is S2 → S0 transition.

Intense emission in the blue (365, 453 and 481 nm) and weaker emission in the red (650–800 nm) were recorded following direct and indirect light excitation of Tm 3+ in POCl 3 :SnCl 4 (8 vol.%) to the 1 D 2 and 1 G 4 levels, located at 27 856 and 21459 cm −1 above the ground state 3 H 6 of Tm 3+ . Time-resolved emission spectra and luminescence decay studies led to average luminescence lifetimes of the 1 D 2 level equal to 23.2 μs and 23.6 μs respectively. They were found to be independent of the concentration of Tm 3+ . The lifetime of the 1 G 4 level, however, was found to vary from 69 to 154 μs for Tm 3+ concentrations ranging from 5.0 × 10 −3 to 5.0 × 10 −2 M. Non-radiative de-excitation of the emitting levels of Tm 3+ is attributed to interactions with the solvent, cross relaxation and interactions with the CT state of Tm 3+ in POCl 3 :SnCl 4 .

Beta-carotene (BC) and canthaxanthine (CX), two carotenoids with and without pro-vitamin A activity, respectively, were found to help to prevent benzo[a]pyrene (BP)-induced skin carcinogenesis in the dark and BP photocarcinogenesis (UV 300-400 nm) when given as an oral supplement to female Swiss albino mice. The same experimental procedure was adapted to 8-methoxypsoralen (8-MOP) photoinduction of mammary carcinomas in mice. Here also, the two carotenoids were strongly antitumorigenic. Indeed, 8-MOP photomutagenesis, tested in S. typhimurium TA 102, appeared to depend on a two-step reaction, namely an oxygen-independent DNA-8-MOP photoadduct, followed by an oxygen-dependent second step, sensitive to carotenoids. This result suggests that dietary carotenoids (powerful antioxidant molecules) might prevent the carcinogenic risk caused by substances that are transformed into ultimate carcinogens by oxidative processes which are indirectly carcinogenic. Finally, to verify whether supplemental carotenoids can affect carcinogenesis where neither light excitation nor oxidative metabolic processes are involved, an experimental attempt was made on gastric carcinogenesis induced in rats by the direct carcinogen N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). The results demonstrate that supplemental carotenoids do not affect initiation and progression stages, but do prevent the progression stage of dysplasias to infiltrating gastric carcinomas. Thus, this provides strong presumptive evidence for oxygen radical involvement in the later stages of this neoplastic development, as recently reported in the literature. As far as mutagenicity in S. typhimurium is concerned, carotenoids do not exert, as expected, any protective effect on MNNG mutagenic activity. The above experimental data suggest that supplemental carotenoids, instead of sunscreen preparations, can be adopted by outdoor workers to prevent skin cancer. Accordingly, such natural antioxidants may be useful in human chemoprevention against neoplasias of the lung, breast, urinary bladder, and colon and rectum even after radical surgery.

By infrared imaging the shape of a strain-confined electron-hole drop in germanium is measured in an applied magnetic field, H ≦ 22 kOe. A considerable distortion from sphericity is observed for all field orientations and stress geometries studied. It is found that in most cases the drop flattens along the field direction. For II ‖〈111〉‖ (applied stress) the drop shape depends markedly on the position of the light excitation spot on the crystal. The dimension parallel to the field decays more rapidly than the perpendicular dimension. The data strongly support a dynamic interpretation in which the recombination currents of electrons and holes give rise to the field-induced distortion. Die Form eines dureh mechanische Spannung lokalisierten Elektron–Loch-Tropfens in Germanium wird mit Hilfe von Ultrarot-Abbildung bei Magnetfeldern, H ≦ 22 kOe, bestimmt. Erhebliche Abweichungen von der Kugelform werden fur alle untersuchten Magnetfeldorientierungen und Spannungsgeometrien beobachtet. In den meisten Fallen flacht sich der Tropfen in Magnetfeld-richtung ab. Fur H ‖〈111〉‖ Spannung hangt die Tropfenforra stark vom Ort des Einfalls des An-regungslichtes ab. Die Tropfengrose parallel zum Feld nimmt schneller ab als die senkrecht zum Feld. Die Mesdaten konnen am besten mit einem dynamischen Modell. indem die Rekombinationsflusse der Elektronen und Locher Anlas zu magnetfeldinduzierter Verformung geben, erklart werden.

Measurements of luminescence decay with L1 light excitation give the same results as with F light excitation, in the temperature range 20–130°K. Also the relative quantum yield temperature dependence agrees with that of the F-light induced luminescence in the range 20–130°K. These results suggest that the fraction L1 states which yield luminescence relax directly to the F+ excited state.

Measurements of Hall mobility as a function of light excitation intensity at room temperature have shown a dependence of Hall mobility on intensity in single crystals of CdS, CdSe, GaAs, InP, and Si. Such a variation of Hall mobility under photoexcitation can result either from (1) a change in the microscopic mobility for single-carrier conductivity, or (2) the initiation of two-carrier conductivity. The recognition of the existence of these effects through photo-Hall measurements is essential for the interpretation of photoelectronic measurements, since simple measurements of conductivity or photoconductivity usually fail to reveal them. Results involving a change in microscopic mobility through photoexcitation indicate a change in scattering associated with the neutralization of charge in centers with an effective scattering cross-section of about 10 −10 cm 2 . A number of other effects resulting from the initiation of two-carrier conductivity have also been explored.

A microfluorometer is applied for simultaneous measurement of DNA content and grain count on a Feulgen stained cell nucleus in an autoradiograph. The autoradiograph is made on a coverslip and mounted on a slide glass with the emulsion side facing downwards. DNA cytofluorometry by incident light excitation can be carried out without interference from the silver grains. Switch-over from DNA cytofluorometry to grain counting is performed instantaneously by changing excitation filters to a red interference filter. The amount of red light reflected by the silver grains is measured by the microfluorometer. The photometric reading gives a value proportional to the grain count. The measurement of DNA content together with grain counting on a cell is completed within a few seconds.

微結晶酸化亜鉛表面における酸素, 無水フタル酸などの化学増感剤が光電導性に与える影響をパルス光を用いた光起電力, 光電流測定で研究した。パルス光照射による観測では酸化亜鉛に履歴現象を生ずることなくキャリヤーの生成・消滅過程を追跡でき, 増感作用に直接関係のある現象に注目できることが分った。特に, 無水フタル酸の増感作用については, 従来物理吸着酸素との相互作用を示唆する結果が報告されているが, 無水フタル酸は表面吸着酸素の光電子捕獲効果を減殺するように作用していると考えられる。また, 微結晶酸化亜鉛では光生成したキャリヤーが初期のうちに再結合して電流に寄与しない割合が無視できないことがわかった。

Two shorter wave-length emission bands have been observed in activated alkali iodides atγ — and light excitation apart from activator emission. The shortest wave-length band, observed only at low temperatures, is excited in exciton absorption bands and it may be due to exciton emission.

Light-induced processes in biological molecules, which occur naturally in continuous incoherent light, are often studied using pulsed coherent light sources. With a focus on timescales, the relationship between excitation due to these two types of light sources is examined through a uniform minimal model of the photoisomerization of retinal in rhodopsin, induced by either coherent laser light or low level incoherent light (e.g. moonlight). Realistic timescales for both processes are obtained and a kinetic scheme involving rates for both coherent and incoherent light excitation is introduced, placing all timescales into a uniform framework. The rate limiting step in the natural light-absorption process is shown to be the low incoherent photon flux.

The ESR of M . radical and solvated electron in K-THF and Rb-THF systems in the presence of dicyclohexyl 18-crown-6 is reported. These species are generated by light excitation via the reaction M − + hv →M . + e. Both species are formed in a non-thermal equilibrium, giving rise to CIDEP. The enhancement factors V are evaluated for K . and for the polarized photoelectrons.

It is shown that local long-life unequilibrium states are generated in Pb1−xSnxTe(In) alloys at the low temperatures under the action of the local light excitation. The character of the photoexcitation propagation in the darkened regions is discussed.

Two ways of performing the Thermally Stimulated Current (TSC) experiment have been used to investigate vapour grown HgI2:i) under light excitation, four peaks are observed at 104, 158, 210, 240 K; ii) under bias excitation, two types of spectra have been obtained with peaks around 160, 240K (type I) and 182, 280 K (type II), respectively. The activation energies have been estimated to be 0.38 eV for the peak showing up at 182 K, and 1.05 eV for the one at 280 K.

This chapter explains the procedure to yield a record of the DNA or RNA position on agarose gels prior to the processing of gel. In this procedure, the ultraviolet-visible (UV) light excitation of ethidium bromide when bound to the DNA or RNA is recorded. The gel is placed on a UV light box and a camera is set to view the image of the gel. Then the film holder is put in place behind the lens and the image is taken. The shutter is opened manually for two to three seconds to develop the film. The same methods are followed while photographing an X-ray film.

It has been suggested by Bloembergen [1] that new resonances should appear in four-wave mixing processes in the case of large damping. These resonances occur when the difference between the frequencies of two beams is equal to a Bohr frequency for two atomic levels which are not directly populated by the light excitation. They have recently been observed by Bloembergen and his coworkers [2]. The original treatment of Bloembergen [1] was performed with the optical Bloch equations. It is well known that the validity of these equations is restricted to a small frequency range where the impact approximation can be applied [3]. We present here the theory of these resonances using the dressed-atom model [3]. The two main advantages of the present theory [4] are (i) a larger range of validity, (ii) a direct comprehension of the physical origin of these resonances.

Electrical signals have been detected in response to light excitation of the fungus Phycomyces blakesleeanus. These signals are related to the wavelength and intensity of the stimulus and the growth stage of the fungus. A relationship between the signals and the possible photoreceptor-pigment system is explored.

The study of the dynamics associated with the production of paramagnetic species or states upon optical pumping has been gaining interest in recent years in a large variety of fields. In this chapter, we confine ourselves to describing the direct epr detection of two groups of transient paramagnetic systems that are generated under light excitation: (a) molecules promoted to their photoexcited triplets and (b) free radicals.

Photodynamic therapy (PDT) of neoplasms using photosensitizers and red light, is currently undergoing clinical trials throughout the world.1 The sensitizer preparation used almost exclusively in PDT consists of a mixture of hematoporphyrin derivatives (HPD) obtained from alkaline hydrolysis of hematoporphyrin acetates.2 The most active compounds in this mixture are believed to be dihematoporphyrin ethers3 and/or esters,4 known as DHE. A commercial preparation enriched in the latter (Photofrin IItm) has been made available for research and clinical trials by Photomedica Inc. The effectiveness of DHE in PDT results from two important properties: (a) selective retention by neoplasms, and (b) induction of cellular damage upon light excitation, most likely through 1O2 formation.5 Advantages of this procedure as compared to conventional cancer treatment modalities include selectivity and low systemic toxicity. A particular advantage of PDT is that it can be applied to recurrences in regions which have already received maximal doses of conventional radiotherapy.

The photophysical properties of phenyl-polyenes have been extensively investigated these last years, from the experimental as well as from the theoretical points of view [1–16]. These compounds play an important role, as chromophores, in the vision transduction mechanism and it is of prime importance to know their molecular dynamics upon light excitation.

— This report describes spectral changes associated with the transformation of metarhodopsin I to metarhodopsin II following light excitation of isorhodopsin and rhodopsin. Irradiated isorhodopsin gives rise to an equilibrium mixture of metarhodopsin I and metarhodopsin II which at 2°C and pH 6.8 favors the former. Isorhodopsin and rhodopsin are converted to metarhodopsin II via metarhodopsin I at very similar rates and activation parameters for the conversions are essentially identical. It is concluded that the initial cis to trans isomerization erases all differences in the two pigments.

In this paper we present a system aimed at demonstrating the photoacoustic (PA) effect for educational purposes. PA imaging is a hybrid imaging modality that requires no contrast agent and has a great potential for spine and brain lesion characterisation, breast cancer and blood flow monitoring notably in the context of fetal surgery. It relies on combining light excitation with ultrasound reception. Our brief was to present and explain PA imaging in a public-friendly way suitable for a variety of ages and backgrounds. We developed a simple, accessible demonstration unit using readily available materials. We used a modulated light emitting diode (LED) torch and an electronic stethoscope. The output of a music player was used for light modulation and the chest piece of the stethoscope covered by a black tape was used as an absorbing target and an enclosed chamber. This demonstration unit was presented to the public at the Bloomsbury Festival On Light in October 2015. Our stall was visited by over 100 people of varying ages. Twenty families returned in-depth evaluation questionnaires, which show that our explanations of the photoacoustic effect were well understood. Their interest in biomedical engineering was increased.

The primary photoinduced charge separation and recombination processes occurring in a dinuclear Ru(II) complex capable to perform multielectron storage upon light excitation have been studied in different solvents: the charge-separated state obtained in dichloromethane is, to the best of our knowledge, the longest-lived ever reported for a ruthenium polypyridine complex.

The photoelectromagnetic effect is studied in single crystals of CuInSe2. A region of light excitation is found in which the dependence of iPEM on light intensity is linear. From the experimental data, a lifetime of the minority carriers τn=0.6×10−9 sec and a surface recombination velocity s=3×105 cm/sec are determined.

We present straightforward evidence of tunneling and transport of electrons from quantum states in a GaAlAs/GaAs/GaAlAs quantum well to a GaAs surface activated to negative electron affinity. The photocurrent versus light excitation energy spectrum shows definite structures which appear at the calculated energies of the allowed optical transitions between the quantized levels of the valence and conduction bands. The magnitude of the structures is in agreement with tunneling predictions. This system could lead to the production of highly polarized electron beams.

The molecular study of energy transfer and luminescent transition mechanisms, and the roles of added activators on the performance of electro-optical effects by double excitation are reported for (Zn, Cd)S : Mn, Cu powders. The excitation sources were uv light and dc field. The highest value of “amplification factor” was about 70 and its brightness was nearly 100 ft-L. From the analyses of date on various samples, following conclusions were deduced. The majority of luminescence centres due to Mn ions are latent under either uv light or dc field. The luminescence from the centres due to Cu ions, corresponding to “G-Cu centres” in ZnS, domainates the one due to Mn ions under uv light excitation. Cu ions also play the roles of a sensitizer under simultaneous excitations. Sulfur vacancies and oxygen atoms make the characters of the centres due to Cu ions effective on double excitation. However, the actions of oxygen are complicated, because the incorporation of oxygen presumably introduces deep traps and makes the two kinds of luminescence centress due to Mn and Cu ions selective to exciting radiation.