共查询到19条相似文献,搜索用时 187 毫秒
1.
2.
3.
本文介绍了用γ共振吸收法测量40Ca 9603.9keV,10321.0keV两组能级和9864.6,9868.8keV一组双重态能级的能级宽度,选用39K(p,γ)反应所放出的γ射线激发相应的40Ca吸收核能级。对于9603.9keV,10321.0keV的能级宽度,这里给出了比较精确的结果,相应的能级宽度分别为Γ=188±47eV,Γ=91±15eV。对于9864.6,9868.8keV能级,结果为Γ=100±24eV,Γ=899±214eV,由于40Ca 9864.6,9868.8keV两能级靠得很近,因此这里用γ共振吸收法测量它们的能级宽度与以往有所不同,将同时有两组γ射线用来激发同样两个能级而发生交叉激发。我们对相应的实验处理方法作了推广。此外,用(p,γ)共振产额法测量了40Ca 9603.9keV,10321.0keV能级宽度,得到了与γ共振吸收法一致的结果。本文还对40Ca 9603.9keV,10321.0keV能级的(p,γ)共振强度Spγ、同位旋T等进行了讨论。
关键词: 相似文献
4.
针对Si/Al掺杂量增大使BaO-(1-x)SiO2-xAl2O3-B2O3-0.005Er3+(x=0,0.5,1,摩尔分数)玻璃样品的1 540 nm红外发光和540 nm上转换发光强度呈现相反的变化趋势,讨论了阳离子掺杂对稀土离子周边对称性和电负性变化与荧光行为的内在关系。红外傅里叶透射光谱显示,不同掺杂浓度下样品的最大声子能量没有明显变化,说明光谱随掺杂浓度的变化与玻璃体系的最大声子能量无关。根据Judd-Ofelt理论计算了4I13/2和4S3/2能级的光学参数,通过比较两能级的跃迁几率(A)、寿命(τ)、荧光分支比(β)和受激发射截面(σ)等光学参数,发现4I13/2能级和4S3/2能级的相关参数呈现相反的趋势。最后测试了样品4I13/2能级下1 540 nm的寿命,进一步从电负性角度考虑了样品的发光效率。理论计算和实验结果相符。 相似文献
5.
6.
对ZBLAN氟锆酸盐玻璃中Pr3+掺杂离子3P0和1D2能级的寿命和发光特性进行了较详细的光谱学研究。首先测量了两种掺杂浓度(质量分数分别为1×10-3,5×10-3)的Pr3+:ZBLAN玻璃的吸收光谱,然后运用时间分辨激光光谱技术测量了3P0和1D2能级在激光单光子共振激发下的荧光发射谱和能级寿命。将不同荧光发射谱带的强度和文献报道的Judd Ofelt理论计算辐射跃迁几率数值做了比较分析,证明了文献中理论计算结果的可靠性。由于浓度猝灭效应,在相同的激发条件下,掺杂浓度为1×10-3样品的荧光发射强度明显大于5×10-3样品的荧光发射强度。但是从我们的测量结果看,掺杂浓度对3P0和1D2 的能级寿命值无显著影响。掺杂浓度为1×10-3时,Pr3+离子3P0和1D2能级的寿命值分别为46,322μs。 相似文献
7.
8.
按照50Nb2O5-(46-x)Y2O3-4Yb2O3-xTm2O3(x=0.1,0.2,0.5,1,2)的配比方式,采用高温固相法制备出了掺杂Tm3+/Yb3+的YNbO4晶体粉末。在980 nm红外光激发下,观测到波长为478,645,707 nm的上转换荧光,分别对应于Tm3+离子的1G4→3H6、1G4→3F4、3F3→3H6能级跃迁过程。利用上转换发射功率与980 nm激光器工作电流关系估算出跃迁过程吸收光子数目为2.72,2.69,2.01,从而确定出前两者为三光子吸收过程,最后一个对应于双光子吸收过程。运用Judd-Ofelt理论研究样品光谱特性,根据样品的吸收谱得到样品的谱线强度参数Ωt(t=2,4,6),进而得出理论振子强度及实验振子强度,二者均方根偏差δrms=1.299×10-7。计算了Tm3+离子向下能级跃迁的跃迁几率、跃迁分支比等参数。最后得出结论:(1)3F4能级寿命较长,适合作为上转换中间能级;(2)3H5能级寿命较长,且3H5→3H6跃迁分支比(96.46%)接近100%,可用于产生1 216 nm激光。 相似文献
9.
用直拉单晶生长系统制备TbyDy1-x(Fe1-xTx)2(T=Al,Mn)单晶,并测量其磁致伸缩.用电弧炉合成多晶TbyDy1-y(Fe1-xTx)2(T=Al,Mn),并用X射线衍射方法测量拟合得到内禀磁致伸缩.结果表明,Al和Mn替代后饱和磁场降低,说明Al和Mn的替代明显地降低了各向异性能.随Al和Mn替代量的增加,总的趋势是材料的内禀磁致伸缩λ111降低.对Tb0.5Dy0.5(Fe0.9Mn0.1)2单晶,在不加压情况下的磁致伸缩效果并不明显,但当施加压力时,磁致伸缩变化显著,尤其在12—26MPa压力下,磁致伸缩变化很大,且低场效果很好.
关键词: 相似文献
10.
11.
本文报导了对以Ni3Al为基的r′单晶体所做的蠕变及持久试验的结果。结果表明,r′晶体的稳态蠕变速εs遵从 εs=Cσmexp(-Qc′/RT) 的关系。指数m仅和温度有关。m(850℃)=3.95,m(950℃)=3.62。对Ni3Al,Qc′=88kcal/g-at。合金元素Ti,Nb,W都使Qc′升高,其中Nb的作用最大,然而W在提高蠕变强度上最有效。晶体取向对εs有显著影响。<111>取向的Ni3Al晶体εs最低,持久寿命tr最长。在1050℃,σ=5kg/mm2时,tr可≥100小时,Ni3Al单晶体也同样符合Monkman-Grant关系tr(εs)p=常数,其中p=0.82。r′晶体蠕变中的滑移系统是{111}<211>。 相似文献
12.
The lifetimes of the first six excited states of 29Al have been measured by the DSA method with two different reactions,26Mg(α, p)29Al and27Al(t, p)29Al. The recoil distance method was also used to remeasure the mean lifetime of the first excited state, leading to a value τm = 6.5 ± 0.5 ps. Experimental results are compared with shell model calculations. 相似文献
13.
The crystal blocking technique has been used to measure the lifetime of the 12.44 MeV 2+ level in 28Si excited in the 27Al(p, α)24Mg resonance reaction at Ep = 885 keV. Both 〈110〉 axial and {111} planar blocking effects in Al single crystals have been investigated. Measurements have been made for two reaction depths, 1000 and 4000 A. Various methods of extracting the lifetime, involving both analytical calculations and computer simulation, are compared. The theoretical change in volume of an axial blocking dip due to a lifetime effect has been calculated in the continuum approximation. The results obtained from the different methods of analysis agree, the average value of the lifetime being 28 as. Although the results show no systematic dependence on reaction depth, pronounced depth effects are evident in computer simulations of the planar blocking dips. 相似文献
14.
H. J. Ong N. Imai D. Suzuki H. Iwasaki H. Sakurai T. K. Onishi M. K. Suzuki S. Ota S. Takeuchi T. Nakao Y. Togano Y. Kondo N. Aoi H. Baba S. Bishop Y. Ichikawa M. Ishihara T. Kubo K. Kurita T. Motobayashi T. Nakamura T. Okumura Y. Yanagisawa 《The European Physical Journal A - Hadrons and Nuclei》2009,42(3):393-396
We have measured the lifetime of the first excited 2+ state in 18C using an upgraded recoil shadow method to determine the electric quadrupole transition. The measured mean lifetime is 18.9±0.9 (stat)±4.4 (syst) ps, corresponding to B(E2;21 + $ \rightarrow$ 0+ gs) = 4.3±0.2±1.0e 2 fm^4, or about 1.5 Weisskopf units. The mean lifetime of the first 2+ state in 16C was remeasured to be 18.3±1.4±4.8 ps, about four times shorter than the value reported previously. The discrepancy is explained by incorporating the $ \gamma$ -ray angular distribution obtained in this work into the previous measurement. The observed transition strengths in 16, 18C are hindered compared to the empirical values, indicating that the anomalous E2 strength observed in 16C persists in 18C . 相似文献
15.
16.
P. A. Loiko N. A. Skoptsov O. S. Dymshits A. M. Malyarevich K. V. Yumashev A. A. Zhilin I. P. Alekseeva 《Optics and Spectroscopy》2016,121(4):497-502
Transparent glass-ceramic materials based on glasses of the MgO–Al2O3–SiO2–TiO2 system doped with CoO and Ga2O3 are synthesized. The secondary heat treatment of the initial glasses at temperatures of 800–950°C leads to precipitation of nanosized (6–7 nm) crystals of magnesium aluminogallium spinel doped with cobalt ions and magnesium aluminotitanate solid solutions. The optical absorption spectra of the initial glass and glass-ceramic materials are studied. It is shown that the absorption band caused by the 4A2(4F)→ 4T1(4F) transitions of tetrahedrally coordinated Co2+ ions in glass-ceramics with nanosized Co:Mg(Al,Ga)2O4 crystals is shifted to longer wavelengths (up to ~1.67 µm) compared to the position of this band in materials with Co:MgAl2O4 crystals. The synthesized glass-ceramics are characterized by a relatively low saturation fluence FS ~ 0.5 ± 0.1 J/cm2 at a wavelength of 1.54 µm, as well as by a high radiation resistance to nanosecond laser pulses, which is no lower than ~15 ± 2 J/cm2. This explains their attractiveness as materials for saturable absorbers for erbium lasers emitting in the spectral range 1.5–1.7 µm. 相似文献
17.
A. A. Vorobyov 《Physics of Atomic Nuclei》2009,72(1):128-140
The rate Λ S of nuclear muon capture by a proton from the hyperfine singlet ground state of the µp atom has been measured using a new experimental method based on a time-projection chamber operating in an ultrapure hydrogen gas at a pressure of 10 atm. The capture rate has been determined from the difference between the measured lifetime of the negative muon in hydrogen and the world average lifetime of the positive muon. The analysis of 10% of the collected statistics (2 × 1010) of µe decays yields the muon capture rate Λ S = 725.0 ± 17.4 s?1, from which the pseudoscalar form factor of the nucleon, g P (q c 2 = ?0.88m µ 2 ) = 7.3 ± 1.1, is determined. The further analysis of the collected experimental data should improve the precision of this measurement by a factor of 3. 相似文献
18.
19.
Yu. K. Voron’ko A. V. Malov K. N. Nishchev P. A. Ryabochkina A. A. Sobol S. N. Ushakov 《Optics and Spectroscopy》2007,102(5):722-727
Based on the analysis of the absorption spectra of Er-doped calcium-niobium-gallium garnet (Er:CNGG) crystals according to the Judd-Ofelt theory, the intensity parameters for these crystals are determined to be Θ2 = 3.43 × 10?20 cm2 Θ4 = 1.20 × 10?20 cm2, and Θ6 = 0.58 × 10?20 cm2. The parameters found are compared with the intensity parameters for other laser oxide crystals. Using these intensity parameters, the probabilities of radiative transitions between the energy levels of Er3+ ions in CNGG crystals and the luminescence branching ratios βJJ’ are calculated. From the measured lifetime of the 4 I 11/2 level of Er3+ ions (τ = 626 μs) and the probability of the radiative transition from this level (A = 192 s?1), it is found that about 88% of the excitation energy in the Er:CNGG crystals is nonradiatively transferred from the 4 I 11/2 to the 4 I 13/2 level. It is suggested that an increase in the oscillator strength and in the line strength of the 4 I 15/2 → 2 H 11/2 transition of Er3+ in CNGG crystals, as well as an increase in the intensity parameter Θ2 with respect to the corresponding parameters for other garnet crystals are caused by the existence in CNGG crystals of Er3+ centers with the environment symmetry lower than D 2. 相似文献