In alkali chlorides heavily doped with Cut ions, CuCl microcrystals of different sizes are grown under different heat treatments. Their size and shape are studied using small-angle X-ray scattering. A clear correlation is established between the microcrystal size and the blue shift of the exciton luminescence peak. The quantum size effect on the exciton is discussed. The exciton confinement, that is, the restriction of the exciton translational motion in one-dimensional quantum wells is found to be rather plausible for CuCl microcrystals in crystalline matrices.Des microcristaux de CuCl de differentes tailles sont fabriquBs par diffbrents traitements thermiques, dans des chlorures alcalins fortement dopes en ions Cu+. Leurs tailles et leur forme sont 6tudi6es par diffusion aux rayons X A petit angle. Une relation bien determinee est mise en Bvidence entre la taille du microcristal et le dbplacement vers le bleu du maximum de la raie de luminescence excitonique. L'effet de quantification dimensionnelle de l'exciton est discuth. Le confinement de l'exciton, c'est A dire la restriction du deplacement de I'exciton dans un puit quantique A une dimension parait &re le mecanisme le plus plausible dans des microcristaux de CuCl enfouis dans des matrices cristallines.

The Palomar Transient Factory (PTF) Orion project is one of the experiments within the broader PTF survey, a systematic automated exploration of the sky for optical transients. Taking advantage of the wide (3. • 5 × 2. • 3) field of view available using the PTF camera installed at the Palomar 48 inch telescope, 40 nights were dedicated in 2009 December to 2010 January to perform continuous high-cadence differential photometry on a single field containing the young (7-10 Myr) 25 Ori association. Little is known empirically about the formation of planets at these young ages, and the primary motivation for the project is to search for planets around young stars in this region. The unique data set also provides for much ancillary science. In this first paper, we describe the survey and the data reduction pipeline, and present some initial results from an inspection of the most clearly varying stars relating to two of the ancillary science objectives: detection of eclipsing binaries and young stellar objects. We find 82 new eclipsing binary systems, 9 of which are good candidate 25 Ori or Orion OB1a association members. Of these, two are potential young W UMa type systems. We report on the possible low-mass (M-dwarf primary) eclipsing systems in the sample, which include six of the candidate young systems. Forty-five of the binary systems are close (mainly contact) systems, and one of these shows an orbital period among the shortest known for W UMa binaries, at 0.2156509 ± 0.0000071 days, with flat-bottomed primary eclipses, and a derived distance that appears consistent with membership in the general Orion association. One of the candidate young systems presents an unusual light curve, perhaps representing a semi-detached binary system with an inflated low-mass primary or a star with a warped disk, and may represent an additional young Orion member. Finally, we identify 14 probable new classical T-Tauri stars in our data, along with one previously known (CVSO 35) and one previously reported as a candidate weak-line T-Tauri star (SDSS J052700.12+010136.8).

Exciton luminescence spectra in CuCI, CuBr, and C u I microcrystals of a few nm in size which are ernbedded in alkali-halide matrices are studied under selective excitation a t the exciton absorption bands inhomogcncously broadened by the size distribution. The size-quantized cxciton states are found to split into various components. From the analysis of the splitting on the basis of the sizequantization of the cxciton translational motion in the microcrystals of thin plateleta, the Z, exciton translational maw, the Luttinger parameters, and k-linear terms for the Zl,2 excitons are derived in these compounds.Les spectres de luminescence excitonique de microcristaux de CuCl, CuBr e t de CuI ayant, des dimensions de quclques nm enfouia dans des matrices de halogbnurea alcalins sont Btudib par excitation sBlectivc dans la bande d'absorption excitonique, celle-ci Btant Blargie de figon inhomoghe & cause dc la distribution en dimension des microcristaux. On obscrvo une sbparation en diffbrentes composantes des Btats excitoniques quantifies en dimension. A partir de I'analyse de cette separation des niveaux nous obtcnons la masse translationnelle de l'exciton Z,, les paramBtrcs de Luttinger do l'exciton ct les tcrmes linthire en k des exciton Zl,2 dans ces trois compods. IntroduetionQuantum-size effects upon electronic excited states have been optically studied in semiconductors with the use of thin films [l to 41, quantum well structures [5], small colloidal crystallites [6 t o 81, microcrystals embedded in solid matrices [9 to 131, and bare microcrystals prepared by the gas-evaporation method [ 141. Excitons in GaAs quantum wells have been most extensively studied, where various fine structures due t o splitting8 of the electronic excited states have been found [5]. However, the Coulomb interaction energy between the electron and the hole inside the excitons is rather small compared with the confinement energies both for electron and hole, and hence, the electron-hole confinement picture is plausible [15].On the other hand, little is known about the quantum-size effect on excitons having large effective Rydberg constant, in which exciton confinement, in other words, quantization of exciton translational motion, is expected to be plausible [la, 161. Recently, Ekimov e t al. have performed optical studies in spherical microcrystals of CuCl dispersed in a transparent silicate glass matrix [ll]. On the basis of the exciton confinement picture, they have explained the energy positions and the profiles of absorption and luminescence spectra of the free exciton bands. However, in their experiments no information has been obtained about the splitting of the size-quantized cxciton states.In our preceding paper 1171 size and shape of CuCl microcrystals embedded in KaCl and KC1 matrices have been studied together with their correlation with exciton confinement. The crystalline shape has been found to be not spherical but somewhat flat, and from the analysis of the relation between the crystalline size and the blue shift I) Send...

Photostimulated luminescence phenomenon was observed in a fluoroaluminate glass doped with Eu2+. When the x-ray irradiated glass was excited by a He–Ne laser (633 nm), photostimulated luminescence at 400 nm due to the 5d–4f transition of Eu2+ ions was observed. X-ray absorption spectra showed that a part of Eu2+ converted to Eu3+ upon the irradiation of x-ray. By comparing with the investigations on photostimulable luminescence phosphor BaFBr:Eu2+, the luminescence appears to result from the photostimulated recombination of holes and electrons at traps, which leave electrons in a long-lived excited state.

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