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1.
Energy transfer from Bi3+ to Nd3+ is reported in germanate glass. It was found that the excitation range and intensities of the 4F → 4I, 4I emissions are increased several fold when excited through 1S0 → 3P1 absorption of Bi3+. It is shown that the energy transfer is nonradiative. The energy transfer probability and efficiency were calculated from the Bi3+ fluorescence decay rates and intensities. The Bi3+ → Nd3+ energy transfer may be utilized in Nd3+ glass laser. 相似文献
2.
The photoinduced processes leading to formation of J-aggregate stacks of 1-(β-methacryloxyethyl)-3,3-dimethyl-6′- nitrospiro-(indoline-2,2′-[2H-[2H-1] benzopyran) d its associated ring opened merocyanine form B have been determined by N2-laser transient spectroscopy. Detailed mechanisms for formation of complexes AB, A2B, and J-aggregate stacks (A2B) n in aliphatic and aromatic solvents are presented. 相似文献
3.
The features of fluorescent glass solar collectors are discussed. Combination of Nd3+ and Yb3+ in high refractive index glasses is suggested as concentration material. Energy absorbed by Nd3+ is transferred with high efficiency to Yb3+ emitting at 970 nm. The self-absorption of Nd3+ is eliminated and long-wavelength emission at 1.06 μm decreased as a result of energy transfer. 相似文献
4.
V.V. Ter-Mikirtychev I.T. McKinnie D.M. Warrington Y. Kalisky S.A. Pollack 《Optics & Laser Technology》1997,29(7):407-410
The characteristics of a 940 nm pumped Cr4+:forsterite laser have been investigated using a pulsed colour centre laser as the excitation source. Laser threshold, slope efficiency and temporal behaviour have been determined for high and low Cr4+ doped material. 940 nm pumping is found to be more efficient than 532 and 730–770 nm excitation. Discrepancies with 1064 nm pumping are attributed to excited state absorption. Absorption saturation measurements have been used to assess the potential applications of Cr4+:forsterite, Cr4+:YAG and Cr4+: Lu3A15O12 (LuAG) as passive Q-switches for Nd lasers in the 940 nm region. 相似文献
5.
Kalisky B Myasoedov Y Shaulov A Tamegai T Zeldov E Yeshurun Y 《Physical review letters》2007,98(10):107001
Magneto-optical measurements of transient vortex states in Bi2Sr2CaCu2O8+delta show enhanced effects of metastability in prism-shaped as compared to platelet crystals including a significant shift of the second magnetization peak and qualitatively different dynamics. In contrast to platelets, where dislocations are generated only at the sample edges, we propose that in prism samples the dislocations are generated dynamically in the entire sample due to distributed surface barriers. As a result, a dynamic phase transition from a Bragg glass to a metastable disordered phase may occur well below the thermodynamic transition field. 相似文献
6.
Effects of sample size on the second magnetization peak (SMP) in Bi2Sr2CaCuO8+δ crystals are observed at low temperatures, above the temperature where the SMP totally disappears. In particular, the onset
of the SMP shifts to lower fields as the sample size decreases —a result that could be interpreted as a size effect in the
orderdisorder vortex matter phase transition. However, local magnetic measurements trace this effect to metastable disordered
vortex states, revealing the same order-disorder transition induction in samples of different size. 相似文献
7.
Kalisky B Aronov P Koren G Shaulov A Yeshurun Y Huebener RP 《Physical review letters》2006,97(6):067003
Measurements of the nonlinear flux-flow resistivity rho and the critical vortex velocity vphi* at high voltage bias close to the instability regime predicted by Larkin and Ovchinnikov (Z. Eksp. Teor. Fiz 68, 1915 (1975) [Sov. Phys. JETP 41, 960 (1976)]) are reported along the node and antinode directions of the d-wave order parameter in the a-b plane of epitaxial YBa2Cu3O7-delta films. In this pinning-free regime, rho and vphi* are found to be anisotropic with values in the node direction larger on average by 10% than in the antinode direction. The anisotropy of rho is almost independent of temperature and field. We attribute the observed results to the anisotropic quasiparticle distribution on the Fermi surface of YBa2Cu3O7-delta. 相似文献
8.
Immunization and epidemic dynamics in complex networks 总被引:1,自引:0,他引:1
N. Madar T. Kalisky R. Cohen D. ben-Avraham S. Havlin 《The European Physical Journal B - Condensed Matter and Complex Systems》2004,38(2):269-276
We study the behavior of epidemic spreading in networks, and, in particular, scale free networks. We use the Susceptible-Infected-Removed (SIR) epidemiological model. We give simulation results for the dynamics of epidemic spreading. By mapping the model into a static bond-percolation model we derive analytical results for the total number of infected individuals. We study this model with various immunization strategies, including random, targeted and acquaintance immunization.Received: 3 November 2003, Published online: 14 May 2004PACS:
02.50.Cw Probability theory - 02.10.Ox Combinatorics; graph theory - 89.20.Hh World Wide Web, Internet - 64.60.-i General studies of phase transitions 相似文献
9.
Nie W. Kalisky Y. Pedrini C. Monteil A. Boulon G. 《Optical and Quantum Electronics》1990,22(1):S123-S131
Multisite energy transfer from Cr3+ to Tm3+ was studied using low-temperature high-resolution laser spectroscopy. Selective excitation routes for Tm3+ sites were demonstrated using excitation and emission spectroscopy, and were confirmed by lifetime measurements. 相似文献
10.
Abstract— The pulsed laser photolysis of light-adapted bacteriorhodopsin (BR570) is carried out over the temperature range between 25°C and—92°C in neutral and alkaline water-glycerol solutions. The results arc indicative of considerable complexity, introduced by two temperature dependent branching reactions associated with the intermediates K610, L550 and M412, of the BR570 photocycle. (a) At relatively low temperatures the primary photoproduct K-610 equilibrates with a blue-shifted species, Kp. Both K610 and the new intermediate subsequently decay into another species, K'r, in a process which competes with the formation of L550. Finally, K'p converts very slowly to L550. This branched pathway delays the formation of L550 and thus of M412, without affecting the final yield of either species, (b) A thermal back-reaction regenerating BR570 takes place at the stage of L550, inhibiting the formation of M412. The reaction which also predominates at low temperatures, is relatively inefficient at high pH when the forward L550→ M412 step is highly catalyzed. It is the superposition of both branching mechanisms, (a) and (b), which accounts for the complex effects of temperature and pH on the photo-cycle of BR570. Mechanism (b) is accounted for by a molecular scheme in which deprotonation of a tyrosine moiety at the stage of L550 constitutes a prerequisite for deprotonation of the retinal-lysine schiff-base as required for forming M412. This scheme appears to be directly related to the proton pump. Mechanism (a) introduces additional complexity in the photocycle at low temperatures but its molecular aspects are still unclear. 相似文献