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41.
Phosphors CaYBO4:RE3+ (RE=Eu, Gd, Tb, Ce) were synthesized with the method of solid-state reaction at high temperature, and their vacuum ultraviolet (VUV)-visible luminescent properties in VUV-visible region were studied at 20 K. In CaYBO4, it is confirmed that there are two types of lattice sites that can be substituted by rare-earth ions. The host excitation and emission peaks of undoped CaYBO4 are very weak, which locate at about 175 and 350-360 nm, respectively. The existence of Gd3+ can efficiently enhance the utilization of host absorption energy and result in a strong emission line at 314 nm. In CaYBO4, Eu3+ has typical red emission with the strongest peak at 610 nm; Tb3+ shows characteristic green emission, of which the maximum emission peak is located at 542 nm. The charge transfer band of CaYBO4:Eu3+ was observed at 228 nm; the co-doping of Gd3+ and Eu3+ can obviously sensitize the red emission of Eu3+. The fluorescent spectra of CaYBO4:Ce3+ is very weak due to photoionization; the co-addition of Ce3+-Tb3+ can obviously quench the luminescence of Tb3+. 相似文献
42.
Vinay Ambegaokar 《Journal of statistical physics》2006,125(5-6):1183-1192
The time development of the reduced density matrix for a quantum oscillator damped by coupling it to an ohmic environment
is calculated via an identity of the Debye-Waller form. Results obtained some years ago by Hakim and the author in the free-particle
limit(10) are thus recovered. The evolution of a free particle in a prepared initial state is examined, and a previously published
exchange(5,9) is illuminated with figures showing no decoherence without dissipation.
PACS number: 03.75.Ss 相似文献
43.
对于2阶Duffing系统与3阶单模激光Lorenz系统,用主动控制方法设计了一种同步控制器,实现二者之间的缩阶反同步。依据罗斯 霍维兹判据,给出误差系统在原点处渐进稳定的条件。数值试验证实:在控制器作用下,2阶Duffing系统的状态变量与3阶单模激光Lorenz投影子系统的状态变量振动的幅值相同但方向相反,且在随机噪声干扰下反同步仍能很好地实现。这表明所设计的控制器对于不同阶的Duffing系统与Lorenz系统的缩阶反同步的实现是可行的、有效的,而且具有很好的鲁棒性。 相似文献
44.
通过Sol-gel(溶胶-凝胶)技术,首次将Al3 离子和K 离子同时引入到掺Er3 硅酸盐玻璃中,并测定了硅基玻璃中Er3 离子的吸收光谱、透射光谱、光致发光光谱(PL谱)、上转换光谱、拉曼光谱及荧光寿命.结果显示:掺入的Al3 离子和K 离子不但分别使Er3 离子的荧光强度增强20倍和70倍,而且使Er3 离子在1 532 nm处的荧光寿命从4.8 ms延长至7.1和11.2 ms,但经过进一步分析可知两者对其的影响机制却完全不同;同时作者发现,在980 nm波长激发下,Er3 离子的上转换荧光应该同时存在两种发光机制:双光子吸收和能量传递上转换. 相似文献
45.
The performance of a superheated alkali vapor cell, with a geometry suitable for x-ray photoionization experiments, is described. An internal heater was used to superheat sodium vapor in a split-wick heat pipe. At a Na pressure of 20 Torr, the transmission through the cell in the region of theC–X molecular band of Na2 increased to 50% from the 5% observed when the cell was operated in a conventional heat-pipe mode. In the presence of a Na atom density of 2×1017 cm–3, the average molecule density over the length of the cell was measured to be 2.5×1015 cm–3. In the hot central region of the superheated cell, the molecule density was predicted to have been reduced by a factor of 50 to 3×1014 cm–3. 相似文献
46.
We present two-photon ionization studies at different uv laser wavelengths (193, 248, 308, and 351 nm) of a series of simple molecules presenting primary, secondary, and tertiary amide groups. In particular, ionic fragmentation patterns at different laser wavelengths and fluences are reported and compared to electron impact mass spectra. The power law for the total ion yield is also discussed. The above studies have been carried out on samples in gas phase at low pressure (10–6 mbar) by using a time-of-flight technique. 相似文献
47.
The energy transfer phenomenon has been studied from Tb3+ → Nd3+ and Tb3+ → Ho3+ in DMSO. A diffusion limited dipole-dipole mechanism of energy transfer is suggested for both systems. At high acceptor concentrations, Pda depends linearly on C2 consistent with the Fong and Diestler theory of energy transfer. However, at low acceptor concentrations the observations of time evolutions of Tb3+ luminescence decay following flash excitation has enabled us to examine diffusion limited energy transfer from Tb3+ to Nd3+ and Tb3+ to Ho3+ in DMSO. 相似文献
48.
A. Tönnißen J. Wanner K. W. Rothe H. Walther 《Applied Physics A: Materials Science & Processing》1979,18(3):297-304
The measurement of the concentration of gaseous hydrogen fluoride in the exhaust of an aluminum plant by resonance absorption
of the radiation of a cw chemical HF laser is reported. The HF concentration has been evaluated taking into account the simultaneous
absorption of water vapor and carbon dioxide at the HF laser frequencies. The absorption cross sections for H2O and CO2 at the HF laser lines have been determined in laboratory experiments. 相似文献
49.
分析了dj图、K图的性质,在此基础上提出了基于dj图、K图的函数CRM展开式在固定极性下最小化的图形方法.它具有直观、简单、易于掌握等特点. 相似文献
50.
J. M. Skowronski 《Annals of Operations Research》1992,37(1):423-437
The Liapunov technique has been introduced in differential games in a sequence of works over the last decade. We discuss application of this technique to the interface between two competitive semi-games, each with different qualitative objective. The feedback information for controllers is provided from designed, analytically integrable state predictors with reduced dynamics, which considerably shortens the computing time. The case is illustrated on the scenario of target reaching before being intercepted, and intercepting before target is reached.Deceased. 相似文献