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791.
792.
Oxygen adsorbed on Pt(111) has been studied by means of temperature programmed thermal desorption spectroscopy (TPDS). high resolution electron energy loss spectroscopy (EELS) and LEED. At about 100 K oxygen is found to be adsorbed in a molecular form with the axis of the molecule parallel to the surface as a peroxo-like species, that is, the OO bond order is about 1. At saturation coverage (θmol= 0.44) a diffraction pattern is observed. The sticking probability S at 100 K as a function of coverage passes through a maximum at θ = 0.11 with S = 0.68. The shape of the coverage dependence is characteristic for adsorption in islands. Two coexisting types of adsorbed oxygen molecules with different OO stretching vibrations are distinguished. At higher coverages units with v-OO = 875 cm?1 are dominant. With decreasing oxygen coverages the concentration of a type with v-OO = 700 cm?1 is increased. The dissociation energy of the OO bond in the speices with v-OO = 875 cm?1 is estimated from the frequency shift of the first overtone to be ~ 0.5 eV. When the sample is annealed oxygen partially desorbs at ~ 160K, partially dissociates and orders into a p(2×2) overlayer. Below saturation coverage of molecular oxygen, dissociation takes place already at92 K. Atomically adsorbed oxygen occupies threefold hollow sites, with a fundamental stretching frequency of 480 cm?1. In the non-fundamental spectrum of atomic oxygen the overtone of the E-type vibration is observed, which is “dipole forbidden” as a fundamental in EELS. 相似文献
793.
Interband magnetoabsorption measurements of a superlattice with GaAs/ GaAlAs layers, thin compared to the cyclotron radius, in a magnetic field parallel to the layers show interband Landau level transitions exclusively for radiation energies falling within the hole and the electron subband width. The data are quantitatively explained with energy levels of a Kronig-Penney model in a parallel magnetic field, and permit a direct observation of the superlattice bandwidth. 相似文献
794.
采用溶胶-凝胶法制备Nafion117/SiO2复合膜.工艺研究表明:复合膜制备过程中,加入的MeOH与TEOS比例基本不影响复合膜的阻钒性能.但如以水解时间10 min,水解完成后自然晾干24 h制备的复合膜,则其VO2+的渗透率最低,为4.27×10-9cm2/s,比Nafion117膜的渗透率降低了52倍.SEM测试表明,经自然晾干的复合膜,其中SiO2晶粒长大,并填充了Nafion膜中大部分的孔洞.以其作隔膜组装全钒氧化还原液流电池(单电池),测试表明膜掺杂后电池的电力效率提高2.7%. 相似文献
795.
Cadmium diffusion into p-type PbTe wafers and out of n-type Cd-diffused PbTe wafers was studied. The electrical properties and Cd content of the wafers showed that only about 150 ppm of the diffused Cd affect the electrical properties of PbTe. The fact that most of the diffused Cd has no effect on the electrical properties of the material is explained on the basis of two different processes of Cd incorporation into the PbTe crystal. 相似文献
796.
In this article , we studied the associated research problems and challenges on routing and wavelength assignment (RWA) in WDM (wavelength division multiplexing) networks. Various RWA approaches are examined and compared.We proposed a new RWA algorithm based on multi-objective. In this new algorithm, we consider multiple network optimizing objectives to setup a lightpath with maximize profit and shortest path under the limited resources. By comparing and analyzing, the pro posed algorithm is much better than the algorithms, which only consider one optimizing objective. 相似文献
797.
全固化非平面单频Nd:YAG环形激光器 总被引:2,自引:3,他引:2
利用Nd:YAG激光增益介质的法拉第效应,以及光束在非平面环形谐振腔中传播产生的偏振面旋转,使激光二极管泵浦的环形Nd:YAG激光器单向运转,获得单频激光输出,最大单纵模激光(1.064μm)输出为365mW,功率波动小于2%,短期频率漂移小于45MHz,并利用内腔倍频技术得到单频绿光输出,最大单纵模绿光(532nm)输出为75mW,功率波动小于4%。 相似文献
798.
H.V. Keer D.L. Dickerson H. Kuwamoto H.L.C. Barros J.M. Honig 《Journal of solid state chemistry》1976,19(1):95-102
Heat capacities have been measured for single crystals of V2O3, either pure or doped with 1 and 1.4 mole% Cr2O3 and Al2O3 over the temperature range 100–700°K. V2O3 undergoes a fairly sharp transition at low temperatures (~170°K) but fails to exhibit any thermal anomaly above 300°K. The thermal behavior of (MxV1?x)2O3, M = Cr, Al, is manifested by two transitions: one at low temperatures, 170–180°K for x = 0.01 and 180–190°K for x = 0.014, and the other at high temperatures. For x = 0.01, the high-temperature (HT) anomaly extended over the range 325–345°K (Cr-doped V2O3) and 345–365°K (Al-doped V2O3), respectively. The corresponding ranges for x = 0.014 were found to be 260–280°K and 270–290°K, respectively. Further, the HT anomaly was characterized by a large hysteresis (~50°K). The values of lattice heat capacity of pure and doped V2O3 were, however, found to be almost the same and could be empirically represented by the Debye (D)?Einstein (E) function with θ values 430°K (T = 100–230°K) and 465°K (T > 230°K), respectively. Further, the enthalpy change ΔH associated with the HT anomaly in doped V2O3 (80 ≤ ΔH ≤ 510 J/mole) was 5–10 times smaller than the ΔH corresponding to the lower-temperature transition. The results cited here appear incompatible with the Mott transition model that has been invoked to explain the HT anomaly. 相似文献
799.
报道了一种基于低非线性系数光子晶体光纤的全光纤高效率超连续谱产生系统。将光纤锁模激光器输出的脉宽5 ps、重复频率20 MHz、平均功率50 mW的脉冲,输入到15 μm的大模场光纤中进行放大,通过与两级芯径较小的短光纤模场匹配缩小输出的模场直径后,输入到20 m低非线性系数的光子晶体光纤,获得的超连续谱波长覆盖范围宽于650~1 700 nm。输入光子晶体光纤的泵浦光功率为740 mW,输出超连续光功率为670 mW,转换效率大于90%。实验研究了超连续光谱展宽的过程,从理论上进行了分析解释。 相似文献
800.
Sylvia A. Gardner Henry B. Gordon Marvin D. Rausch 《Journal of organometallic chemistry》1973,60(1):179-188
Metalluorene complexes (π-C5H5)M(CO)(C12H8) (IVa)-(IVc) and (π-C5H5) (CO)(C12F8) (IVd)-(IVf) (M = Co, Rh and Ir) have been prepared from reactions of the appropriate (π-cyclopentadienyl) carbonylmetal diiodides with 2,2′-dilithhiolbiphenyl (IIa) and 2,2′-dilithiooctafluorobiphenyl (IIb), respectively The triphenylphoshine substitution reactions of cobalt compounds (IVa) and (IVd) have also been studied. Reaction of (IIa) and (IIb) with norbornadieneplatinum dichloride result in the preparation of metallocyclic platinum compounds (π-C7H8) and (π-C7H8)Pt(C12H8). A reaction of (IIb) with zirconocene dichloride produces (π-C5H5)2Zr(C12F8), the first example of a ziconium-containing metalofluorene. 相似文献