| 1. |
- Chen, W, et al.
(författare)
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Pressure dependence of Mn2+ fluorescence in ZnS:Mn2+ nanoparticles
- 2000
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Ingår i: Journal of Luminescence. - 0022-2313. ; 91:3-4, s. 139-145
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Tidskriftsartikel (refereegranskat)abstract
- The photoluminescence of Mn2+ in ZnS : Mn2+ nanoparticles with an average size of 4.5 nm has been measured under hydrostatic pressure from 0 to 6 GPa. The emission position is red-shifted at a rate of −33.3±0.6 meV/GPa, which is in good agreement with the calculated value of −30.4 meV/GPa using the crystal field theory.
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| 2. |
- Mohan, R. K., et al.
(författare)
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Photon-echo amplification and regeneration for optical data storage and processing
- 2000
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Ingår i: Journal of Luminescence. - 0022-2313. ; 86:3-4, s. 383-390
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Tidskriftsartikel (refereegranskat)abstract
- Optical data storage devices and erasable memories with storage densities in the range of terabits/cm2, all-optical devices for communication like optical bit-rate converters, routers and image processors can become a reality with photon-echo-based frequency-selective materials. In photon-echo-based optical data storage and data processing the photon-echo-output intensity generally is about 0.1–1% of the input intensity. Many devices, such as processors would require that the photon-echo output is used as an input to a new photon-echo process and hence the amplification of photon-echo signals is necessary. In this paper we describe the development of a fibre amplifier for amplifying photon-echo data. Requirements and performance for the fibre amplifier are discussed. Some examples of our initial experiments, where photon-echoes amplified by the fibre amplifier are used to generate secondary photon-echoes, are also presented.
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| 3. |
- Nagirnyi, V, et al.
(författare)
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Separation of excitonic and electron-hole processes in metal tungstates
- 2003
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Ingår i: Journal of Luminescence. - 0022-2313. ; 102, s. 597-603
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Tidskriftsartikel (refereegranskat)abstract
- Absorption, reflection and emission polarization spectra of CdWO4 crystals have been studied in the region 3.5-30 eV in order to distinguish the excitonic and electron-hole processes in the vicinity of the band gap. The following parameters have been defined from the Urbach tail study at 6-300 K: E-0 = 5 eV, sigma(0) = 0.31, homega = 70 meV (565 cm(-1)). Excitonic processes have been shown to dominate at excitation of tungstate crystals in the lower part of the conduction band. Excitons are formed due to the transitions into the tungstate W5d states hybridized with O6p and possess a very strong tendency for self-trapping. Free electrons and holes can be created at the energies 1-2 eV (depending on the crystal) higher than the bottom of the conduction band due to the transitions into cationic states. (C) 2003 Elsevier Science B.V. All rights reserved.
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| 4. |
- Robert-Philip, I., et al.
(författare)
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Generation of non-classical light by single quantum dots
- 2003
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Ingår i: Journal of Luminescence. - 0022-2313. ; 102-103:SPEC, s. 67-71
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Konferensbidrag (refereegranskat)abstract
- The emission statistics of single semiconductor quantum dots is investigated in view of generating quantum states of light. Correlation experiments show that the emission of a quantum dot can be regulated so as to produce only one photon at a time as well as correlated photon pairs. This observation opens the way to the use of semiconductor quantum dots as triggered sources of single photons, which could find applications in quantum cryptography. We then discuss the potentiality of quantum dots for the production of mutually coherent single photons as well as entangled photons that could be used in quantum information processing schemes. © 2002 Elsevier Science B.V. All rights reserved.
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| 5. |
- Dedic, R, et al.
(författare)
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Hole burning study of cyanobacterial Photosystem II complexes differing in the content of small putative chlorophyll-binding proteins
- 2004
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 107:1-4, s. 230-5
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Tidskriftsartikel (refereegranskat)abstract
- This contribution presents low-temperature absorption, both broad-band and site-selective excited fluorescence, and persistent hole burning spectra of Photosystem II complexes from the Photosystem I-lacking strains of the cyanobacterium Synechocystis sp. PCC 6803 differing in the content of small putative chlorophyll-binding proteins (Scps). These proteins are homologous to light-harvesting complex of higher plants and may bind pigments. The excited state lifetimes of the complexes were determined from zero-phonon hole widths extrapolated to zero-burning dose. The area and spectral position of a phonon side-band with respect to the zero-phonon hole provided additional information concerning chlorophyll–protein coupling and the Stokes shift. Decrease of three absorption subbands at (670.0, 672.9, and 675.7 nm) in the Photosystem II isolated from the strain lacking ScpC and ScpD is in agreement with a hypothesis about the role of Scps in the chlorophyll binding. In addition, narrowing of the zero-phonon hole in Photosystem II without both Scps indicates slowering of the excitation energy transfer which may be explained by the absence of a protective excitation energy quenching related to the presence of Scps.
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| 6. |
- Hughes, Joseph L, et al.
(författare)
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Photoconversion of chlorophylls in higher-plant CP43 characterized by persistent spectral hole burning at 1.7 K.
- 2004
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 108:1-4, s. 131-136
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Tidskriftsartikel (refereegranskat)abstract
- The chorophyll-protein complex CP43 is a proximal-antenna subunit important for excitation energy transfers from peripheral light-harvesting antenna to the Photosystem II (PSII) reaction centre. We report persistent spectral hole burning at 1.7 K in the Qy(0,0) origin and Qy(1,0) vibrational satellite bands of chorophyll a (chl a) in CP43 isolated from higher plants. The isolated CP43 is known to possess two quasi-degenerate 'red' trap states. We find persistent hole burning in the primary trap exhibits a photoconversion property, with a photoproduct located well outside its inhomogeneous distribution. This photoconversion of trap chl a molecules also occurs with non-selective white light illumination. The contribution of the 'red' states to CP43 absorption is discussed.
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| 7. |
- Ionescu, Ruxandra, et al.
(författare)
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Eu(III) complexation of phenyltrisalanine and phenylbisalanine in aqueous solution studied by photoluminescence and UV spectroscopy
- 2004
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 106:2, s. 133-139
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Tidskriftsartikel (refereegranskat)abstract
- The Eu(III)-coordination of phenyltrisalanine (Pta) 1, in aqueous solution was investigated. The photoluminescence data suggested that the chelating effect of Pta places the metal ion on the face of the aromatic ring as proposed in 4. Furthermore, Eu(III) is usually used as a substitute for Ca(II) in spectroscopic studies and the formation of a 1:1 complex between Pta and Eu(III) indicated the possibility that Pta may be used as a Ca(II) binder. For comparison, phenylbisalanine (Pba) 2, was subjected to similar studies and was found to behave more like phenylalanine. (C) 2003 Elsevier B.V. All rights reserved.
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| 8. |
- Peterson Årsköld, Sindra, et al.
(författare)
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Low-temperature spectroscopy of fully active cores. Comparison with CP43, CP47
- 2004
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 108:1-4, s. 97-100
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Tidskriftsartikel (refereegranskat)abstract
- Comparisons of absorption spectra of photosystem II (PSII) core complexes with those of isolated CP43, CP47 and D1/D2/cyt b559 complexes show broadenings and shifts upon disassembly of the PSII core material. Spectra of PSII cores isolated from plants and cyanobacteria reveal marked changes in energies and intensities of the sharp features associated with P680. Low-temperature, illumination-induced electrochromic shifts in PSII cores allow identification of an excitation localized on pheopytin-a (pheo a) in D1. A weak interaction between an exciton component of P680 and the D1 pheo a, both located near 684 nm, is suggested. MCD spectra of 5- and 6-chlorophyll a D1/D2/cytochrome b559 preparations provide links to photoactive pigments in intact PSII cores.
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| 9. |
- Prince, Barry J, et al.
(författare)
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Persistent spectral hole burning from oxygen-evolving Photosystem II cores from cyanobacteria and higher plants
- 2004
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Ingår i: Journal of Luminescence. - : Elsevier BV. - 0022-2313. ; 108:1-4, s. 101-105
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Tidskriftsartikel (refereegranskat)abstract
- Persistent spectral hole burning was performed on active Photosystem II (PSII) cores from spinach and Synechocystis 6803, each containing about 32 chl a molecules per core. Hole-burning action spectra are presented. The data appear inconsistent with a mechanism involving non-photochemical hole burning, as has previously been observed in isolated PSII protein-pigment fragments. A photochemical hole-burning mechanism involving charge separation in P680 accounts for the features of the spectra presented.
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| 10. |
- Spedding, G R, et al.
(författare)
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A family of vortex wakes generated by a thrush nightingale in free flight in a wind tunnel over its entire natural range of flight speeds
- 2003
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 1477-9145 .- 0022-0949. ; 206, s. 2313-2344
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Tidskriftsartikel (refereegranskat)abstract
- In view of the complexity of the wing-beat kinematics and geometry, an important class of theoretical models for analysis and prediction of bird flight performance entirely, or almost entirely, ignores the action of the wing itself and considers only the resulting motions in the air behind the bird. These motions can also be complicated, but some success has previously been recorded in detecting and measuring relatively simple wake structures that can sometimes account for required quantities used to estimate aerodynamic power consumption. To date, all bird wakes, measured or presumed, seem to fall into one of two classes: the closed-loop, discrete vortex model at low flight speeds, and the constant-circulation, continuous vortex model at moderate to high speeds. Here, novel and accurate quantitative measurements of velocity fields in vertical planes aligned with the freestream are used to investigate the wake structure of a thrush nightingale over its entire range of natural flight speeds. At most flight speeds, the wake cannot be categorised as one of the two standard types, but has an intermediate structure, with approximations to the closed-loop and constant-circulation models at the extremes. A careful accounting for all vortical structures revealed with the high-resolution technique permits resolution of the previously unexplained wake momentum paradox. All the measured wake structures have sufficient momentum to provide weight support over the wingbeat. A simple model is formulated and explained that mimics the correct, measured balance of forces in the downstroke- and upstroke-generated wake over the entire range of flight speeds. Pending further work on different bird species, this might form the basis for a generalisable flight model.
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