A SrGa 2 S 4 :Eu phosphor was synthesized using a decomposition method without the use of toxic H 2 S gas. SrGa 2 S 4 :Eu and ZnCdS:Ag,Cl phosphors were chosen to produce green and red emissions, respectively, under excitation from a blue light emitting diode ͑LED͒. A three band white LED was obtained through a combination of nonabsorbed blue emission from a blue LED and green and red emissions from the SrGa 2 S 4 :Eu and ZnCdS:Ag,Cl phosphors. The optical properties of the three band white LED are also discussed.There has been much interest in light emitting diodes ͑LEDs͒ that emit light from ultraviolet to infrared. Major developments in wide bandgap III-V nitride compound semiconductors have led to the commercial production of high efficiency LEDs. 1,2 Traditional colored LEDs have proven themselves in signal applications, as indicator lights, and in automotive lighting. Development of white LEDs is important for expanding LED applications toward general lighting, where the opportunities are enormous. Recently, efficient blue and green LED devices were developed. Green and blue InGaN technology makes possible the first white light LED in which white light is obtained by mixing the outputs of red, green, and blue LEDs. Unfortunately, combining multiple LEDs produces a poor white. The variation of LED color properties due to manufacturing tolerances makes the multiple LED impractical. Moreover, the various LEDs experience different light output degration rates, which will produce different color temperatures over time.To solve these problems, a blue LED chip coated with a Y 3 Al 5 O 12 :Ce phosphor was used to provide a white light emitting diode ͑conventional white LED͒ with correlated color temperatures ranging from 4,000 to 11,000 K. 3,4 The phosphor Y 3 Al 5 O 12 :Ce emits yellow luminescence, and the combination of blue emission from a blue LED and yellow emission from the Y 3 Al 5 O 12 :Ce is perceived by the human eye as white light. This simple structure avoids the need to control a consistent red-green-blue emission ratio from a multiple LED. However, this white light does not have high color rendering properties. Moreover, various phosphors with different components must be synthesized in (Y 1Ϫx Gd x ) 3 (Al 1Ϫy Ga y ) 5 O 12 :Ce phosphors in order to get different color temperatures of the white LED. To improve color rendering of the white LED, a white LED based on three emission bands ͑three-band white LED͒ must be developed. To fabricate a three color white LED by using a blue LED with green and red phosophor coatings, we do not need to synthesize various (Y 1Ϫx Gd x ) 3 (Al 1Ϫy Ga y ) 5 O 12 :Ce phosphors. Various color temperatures are obtainable by controlling the amounts and ratios of the green and red phosphors. From experience with white lamps, we know that three band white lamps have several advantages over conventional white lamps. First, the human eye senses a greater brightness although the luminance level is equivalent. Second, light from three-band white lamps reproduces object colors mo...

The authors studied the Li concentration dependence of the internal efficiency and extraction efficiency contributions to the enhanced photoluminescence (PL) brightness of the Li-doped Y2O3:Eu thin films. Experiments conducted with excitation at a wavelength of 254nm showed that adding 20mol% Li2CO3 to conventional Y2O3:Eu thin films improved their PL brightness by a factor of over 7.0. This improvement is attributed to enhanced internal factors (crystallinity, grains, and substitution of interstitial oxygen) and the increased optical volume (thickness), as well as the reduction of photon trapping in the high-index guiding layers of the Y2O3:Eu thin films. They also discuss how to quantitatively determine the contributions of the internal efficiency, the extraction efficiency, and the optical volume to the enhanced PL brightness of the Li-doped Y2O3:Eu thin-film phosphors.

In this review, we summarize the recent findings on novel narrow-band red phosphors, the improved color and visual energy properties of these phosphors, and their ability to improve the optical properties of corresponding warm white pc-WLED lightings.

We report measurement of the HD product quantum state distributions and absolute cross section for the H+CD4→HD(v′,J′)+CD3 reaction at a collision energy of 1.5 eV. The total reaction cross section is small, 0.14±0.03 Å2, making the experimental measurements difficult. The HD quantum state distribution peaks at low J′ in both v′=0 and v′=1, the only vibrational states in which product is observed. Very little of the 1.5 eV available energy appears as internal excitation of the HD product molecule, 7% in HD product vibration and 9% in rotation. However, linear surprisal analysis shows that this limited internal energy disposal in the HD product in some ways exceeds that expected statistically, since two of the best-fit surprisal parameters (Θr=2.9±0.6 for v′=0, Θr=−1.9±0.5 for v′=1, λv=−2.2±0.6 ) are negative. The HD rovibrational state distribution shows an anomalous positive correlation of product vibrational and rotational excitation. Those molecules formed in the vibrationally excited state, v′=1, have significantly more rotational energy (〈Erot〉=0.17 eV) than those molecules formed in the vibrational ground state, v′=0 (〈Erot〉=0.13 eV). This behavior runs counter to the otherwise universal behavior for direct bimolecular reactions—a negative correlation of product vibrational and rotational excitation. We speculate as to the source of this anomalous energy disposal.

These results demonstrate that the simultaneous acquisition of PET and MR images is feasible using the MR insertable PET developed in this study.

This work presents the synthesis, structure determination and magnetic properties of a new complex, phenethylammonium tetrachloromanganate(II), (C(6)H(5)CH(2)CH(2)NH(3))(2)MnCl(4) (Mn-PEA). Single crystals of Mn-PEA were obtained from methanol solution using the solvent-evaporation method at room temperature. The crystal structure of Mn-PEA was determined by single-crystal X-ray diffraction (orthorhombic, space group Pbca, a = 7.2075(9), b = 7.3012(14), c = 39.413(6) Å and Z = 4). The structure consisted of an extended [MnCl(4)](2-) network and two phenethylammonium cations to form a two-dimensional halide perovskite structure. Temperature-dependent magnetization measurements indicated that Mn-PEA acted as a weak ferromagnet below T(C) = 44.3 K due to spin canting. Below T(C), the magnetic behavior differed significantly from the behavior commonly observed among weak ferromagnets. The susceptibility depended strongly on the crystal orientation, the external magnetic field strength, and the magnetic history. The isothermal magnetization for two orientations revealed a ferromagnetic moment with a spin-canting angle of 0.04° and a spin-flop transitions with H(sf) = 3.5 T. The weak ferromagnetism, which manifested as spontaneous magnetization and magnetic hysteresis near a field strength of zero, was driven by interplay between the easy axis and the antisymmetric Dzyaloshinsky-Moriya (DM) interaction, leading to directional dependent magnetic behavior.

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A magneto-optically active thin film of Rb j Co k [Fe(CN) 6 ] l ·nH 2 O has been prepared using a sequential assembly method. Upon irradiation with light and at 5 K, the net magnetization of the film increased when the surface of the film was oriented parallel to the external magnetic field of 0.1 T. However, when the surface of the film was perpendicular to the field, the net magnetization decreased upon irradiation. The presence of dipolar fields and the low-dimensional nature of the system are used to describe the orientation dependence of the photoinduced magnetization.The ability to increase or decrease the photoinduced magnetization by changing the orientation of the system with respect to the field is a new phenomenon that may be useful in future device applications.