Papers by Keyword: Decay Time

Abstract: There are many products that produce sound when external force is applied to metals and alloys, such as wind chimes, golf clubs, and metal bats. Previous studies have investigated the differences between acoustic properties and sound impressions of these products depending on the type of material. Sound is an element that influences the comfort in our daily lives and the sensation of players in sports. Therefore, it is important to clarify the differences in acoustic properties of different materials in order to design and improve products. However, the effects of changes in chemical composition in the same material on acoustic properties have not been sufficiently studied. The purpose of this study is to evaluate the change in acoustic properties due to the chemical composition of metals and to contribute to the acoustic design of products. In this study, six types of brass specimens with varying zinc content from 5% to 40% were prepared, and the differences in frequency and decay time of hitting sound were evaluated. As a result, it was confirmed that the frequency tended to decrease as the zinc content increased, and the decrease in frequency was particularly pronounced for the specimens with a zinc content of 40%. Attenuation time showed an increasing trend but decreased slightly for specimens with 40% zinc content. These results indicate that the chemical composition of brass has a significant effect on acoustic properties.

Abstract: The red phosphor (TiZn₂O₄) is formed from TiO₂ and ZnO via simple solid-state reaction. This red phosphor is prepared by chemically stable as well as inexpensive oxide materials. Emission and excitation spectra are investigated for this phosphor. Photoluminescence (PL) measurements reveal that this phosphor emits bright red emission at 611 nm, which is associated with ⁵D₀ – ⁷F₂ transition, with near UV (395 nm) and blue light excitation (470 nm). The measured decay time of this red emission can be fitted well with a fast decay time of 67 ms and a slow decay time of 208 ms, respectively. A broad grain size distribution is observed for TiZn₂O₄ phosphor. Further, photoluminescence excitation (PLE) shows a good absorption band near UV, and the blue spectral region of visible spectrum as well. The optical properties, X-ray diffraction (XRD) measurements, and scanning electron micrographs (SEM) of this TiZn₂O₄ phosphor are studied.

Abstract: LYSO:Ce crystal is one of efficient scintillation materials with high light output and short decay time. LYSO:Ce crystal grown by Czochralski method can be affected by annealing treatments. In present work, annealing treatments in different atmosphere (air, N₂ and H₂) were carried out on the LYSO:Ce crystals to investigate the effect on the optical and luminescence properties after annealing. The optical transmittance, excitation and emission spectrum, and the decay time have been attained at room temperature. Luminescence efficiency has been presented by the integrated area of emission spectra under ultraviolet (UV) excitation. It is found that annealing treatments almost do not affect the optical transmittance. Annealing in N₂ atmosphere has no noteworthy effect on the luminescence intensity of LYSO:Ce crystals, but increases much annealing in H₂ atmosphere, dramatically decreases the luminescence intensity after annealing in air. In addition, the decay time of LYSO:Ce crystals are affected by annealing treatment either in air or in H₂ atmosphere.

Abstract: High quality thin epitaxial films of Lu₃(Ga,In)₅O₁₂:Eu³⁺ were grown by liquid phase epitaxy (LPE) method from Bi₂O₃-based flux. Excitation and emission spectra as well as luminescence decay kinetics of Lu₃(Ga,In)₅O₁₂:Eu³⁺ epitaxial films were studied under UV excitation. The photoluminescence spectra of Eu³⁺ ions in Lu₃(Ga,In)₅O₁₂:Eu³⁺ are characteristic to the f→f transition in the Eu³⁺ ions that occupied dodecahedral sites in the garnet structure. The efficient energy transfer between Bi³⁺→Eu³⁺ is observed at the excitation of Lu₃(Ga,In)₅O₁₂:Eu³⁺ films in Bi³⁺ excitation band with maximum at 288 nm. The Eu³⁺ decay curves of all investigated films show non-single exponential behavior at room temperature.

Abstract: The aggregation of urine crystallites with different sizes in the urines of 5 cases of uric acid (UA) calculi patients and 5 cases of healthy controls were comparatively investigated by means of nanoparticle size analyzer. Different sizes of urine crystallites were obtained by filtrating the urine through microporous membrane with different pore sizes (0.22, 0.45, 1.2, 3, and 8 μm), respectively. The average particle size () increased rapidly with placement time (t) in the lithogenic patients. The values of the urine crystallites of the controls increased more slowly with t. When t was increased, the autocorrelation curves in the two types of urine crystallites became less smooth and the decay of the correlation curve became slower, and decay time of different sizes of urine crystallites both for the calculi patients and the controls increased. These results indicated that the urine crystallites of the controls were more stable than those of the patients. The rapid aggregation of urine crystallites may be an important factor affecting the growth of crystallites in UA stone patients.

Abstract: The fluorescence lifetime of the molecular excited states in the liquid scintillator determines the pulse shape of the events in a detector. The fluorescence decay times of the mixtures could be measured by UV light excitation, or via ionizing particles. Both of the setups are based on the time-correlated single photon technique. In this paper we described a setup in detail for testing the fluorescence lifetime under ionizing particle to render the relatively weak neutron or ion signals detectable. In addition, we presented the time resolution of system for the setup.

Abstract: Abstract. Excitation and emission spectra under UV and X-ray excitations, as well as the luminescence decay kinetics of Gd₃Ga₅O₁₂: Bi single crystalline films were studied. The emission spectra observed in the spectral region 350-700 nm at room temperature consist two elementary bands peaked at 446 and 521 nm. The influence of growth conditions on the luminescent properties of Gd₃Ga₅O₁₂: Bi³⁺ garnet have been revealed. The integral and relative intensities of the luminescence bands depend on the excitation wavelength. The Bi³⁺ decay curves of all investigated films show non-single exponential behavior at room temperature.

Abstract: A report on the crystal growth, luminescence and scintillation characteristics of two developed scintillators, CsCe2Cl7 and Cs2NaCeCl6 are presented. CsCe2Cl7 is a new scintillation material. These crystals were grown by the Czochralski pulling technique. The X-ray diffraction technique was used to verify the structure of crystals. Under the X-ray excitation emission, the CsCe2Cl7 showed a broad emission band in the wavelength range from 370 to 470 nm while the Cs2NaCeCl6 crystal showed a spectrum in the wavelength range from 370 to 440 nm. The energy resolutions (FWHM of peak position) for the 662 keV full energy peak of 5.5% and 8.3% were observed at room temperature for the CsCe2Cl7 and Cs2NaCeCl6 crystals, respectively. The scintillation decay time measurement curves showed that, CsCe2Cl7 crystal has a single exponential decay function with a decay time of 50 ns. The Cs2NaCeCl6 crystal exhibited three main decay time components, a short component with a decay time constant of 91 ns and 36% intensity, an intermediate component with a decay time constant of 601 ns and intensity 33%, followed by a long component with a 3.2 µs decay time constant and an intensity of 31% of the total light yield. On the basis of the scintillation results of these materials grown, it is believe that these scintillation crystals can find a place in medical imaging and radiation detection system.

Abstract: Self –organized InAs quantum wires (QWRs) were fabricated on the step edges of GaAs (331)A surface by molecular beam epitaxy (MBE). The atomic force microscopy (AFM) results show that the lateral size of InAs QWRs is 90 nm while the size along the step lines increasing with the thicknesses of InAs layers, amounting to 1100nm. The height of InAs QWRs varies from 7.9nm to 13nm. Photoluminescence (PL) measurements on the two samples were explored and an obvious PL peak around 967 nm was observed at 25 K. The PL intensity decreases as the temperature increases, and it will vanish above 60 K. However, the QWR sample with thicker InAs layer emits a long emission of 1100 nm -1400 nm as the temperature rises above 50 K, and a longer emission of 1400-1600nm as the temperature approaches to 100 K. We considered that the complex photoluminescence spectra were originated from the multiple energy steps. The carrier migration among the different QWRs structures intensified with temperature, and the chance rate from the higher energy levels to the lower ones which generated a stronger emission of long wavelength. The carrier dynamics of QWR samples were measured by using time resolved PL (TRPL) spectra from 25 K to 100 K. The PL decay time in the QWR structure at longer emission was found to be independent of the temperature as T<100 K, showing a typical dynamical behavior of the localized excitons.