LIFETIMES OF RYDBERG LEVELS IN THE PERTURBED 6SNP P-1,3(1) SERIES OF YBI

Using two methods: (1) three-step excitation and (2) single UV photon excitation in an atomic beam with direct observation of the decay of the fluorescence light, we have measured the lifetimes of the Rydberg levels of YbI belonging to the perturbed series 6snp J = 1 levels. The measured values have been interpreted by the multichannel quantum defect theory (MQDT).

LIFETIMES OF RYDBERG LEVELS IN THE PERTURBED 6SNP 3P2 SERIES OF YTTERBIUM-I

Using three-step laser excitation in an atomic beam and a time-resolved spectroscopy technique, we measured both the lifetimes of the Rydberg levels of Yb I belonging to the perturbed series 6nsp 3P2 and the lifetimes of the perturbing 4f(13)5d(2)6s 3P2, 1D2 levels. An expected shortening has been observed for the lifetimes of those levels which are strongly mixed with the perturbers.

NATURAL RADIATIVE LIFETIMES OF THE EXCITED-LEVELS OF THULIUM

The radiative lifetimes of eight excited levels of thulium have been measured with the method of stepwise excitation from the 4f13(F-degrees-7/2)6s2(1S0)\7/2\ ground state to the states studied using two pulsed dye lasers. Optical transients were recorded through observing fluorescences and evaluated with regard to the decay time. The accuracy of the measured lifetime values is about 10%.

MEASUREMENT AND CALCULATION OF SPONTANEOUS EMISSION BRANCHING RATIOS, RELATIVE OSCILLATOR-STRENGTHS, TRANSITION-PROBABILITIES AND LEVEL LIFETIMES FOR ATOMIC URANIUM

We propose a laser induced sensitized fluorescence spectrometry for measuring the spontaneous emission branching ratios o?the transitions from the ten levels 5f36d7s7p-7M7, 5f36d7s7p-7L6, 5f37s27p-5K6, 5f26d27s2 - 5L7, 5f46d7s - 7L6, (17,070cm-1)-5L6, 5f26d27s2-5K6, 6d7s7p-7L5, 5f36d7s7p-7K5 and 5f26d27s2-5I5 to the ground state of atomic uranium (UI) for the first time. Their relative oscillator strengths have been measured by means of hollow cathode discharge (HCD) emission spectrometry. The radiative...

Measuring Receptor/Ligand Interaction at the Single-Bond Level: Experimental and Interpretative Issues

There is increased interest in measuring kinetic rates, lifetimes, and rupture forces of single receptor/ligand bonds. Valuable insights have been obtained from previous experiments attempting such measurements. However, it remains difficult to know with sufficient certainty that single bonds were indeed measured. Using exemplifying data, evidence supporting single-bond observation is examined and caveats in the experimental design and data interpretation are identified. Critical issues preventing definitive proof and disproof of single-bond observation include complex binding schemes, multimeric interactions, clustering, and heterogeneous surfaces. It is concluded that no single criterion is sufficient to ensure that single bonds are actually observed. However, a cumulative body of evidence may provide reasonable confidence. 0 2002 Biomedical Engineering Society.

K9玻璃薄膜对离子交换磷酸盐玻璃波导表面保护的优化研究

采用镀K9玻璃薄膜方法来解决离子交换掺铒磷酸盐玻璃波导表面的侵蚀问题,对K9玻璃薄膜的厚度进行了优化研究。测量分析了样品的荧光光谱和荧光寿命,采用光学显微镜和棱镜耦合技术对不同K9玻璃薄膜厚度下制备波导的表面形貌和导光特性进行了表征和测试。结果表明,与掺铒磷酸盐玻璃原材料相比,镀K9玻璃薄膜后荧光光谱保持不变,荧光寿命稍有下降(约0.2 ms);K9玻璃薄膜的厚度在60~80 nm的范围内保护效果最佳。为下一步制备掺铒有源玻璃光波导器件奠定了良好的实验基础。

Nd3+螯合物的含氢有机溶液光谱性能研究

Tris-thenoyltrifluroacetonate of Nd3+ has been prepared and dissolved in DMF solation with very high concentration, and the contained hydrogen has not been substituted by deuterium. The absorption spectrum, emission spectrum, and fluorescence lifetime of the solution were measured. Very obvious characteristic fluorescence peaks were observed at 898 and 1058 nm. Based on Judd-Ofelt theory, three intensity parameters were obtained: Omega(2) = 4.9 x 10(-20) cm(2), Omega(4) = 5.1 x 10(-20) cm(2) and Omega(6) = 2.5 x 10(-20) cm(2). Line strengths S-cal, oscillator strengths f(cal), radiative transition probabilities A(ed), radiative lifetimes tau(r) and branch ratios beta were calculated too. The measured lifetime tau of 1058 nm peak is 460 mu s, and that of 898 nm 505 mu s. Comparison between theoretically computed radiative lifetime tau(r)(682 mu s) and the measured lifetime indicates that the non-radiative transition probability of the solution is very low and the fluorescence quantum efficiency very high. High values of three intensity parameters prove the high asymmetric surroundings of Nd3+, which is important for Nd3+ to absorb the excitation energy. Spectropic quality factor Omega(4)/Omega(6) > 1 makes radiation at 898 nm stronger than at 1058 nm.

新型掺铒离子氧氟碲酸盐玻璃的光谱性质

探求新的具有优良的热学和光学性能的基质玻璃系统，是获得具有宽带宽和增益平坦的掺Er^3＋光纤放大器（EDFA）的一种有效途径。制备了一种新型氧氟碲酸盐玻璃TeO2-BaF2-LaF3，并对其热学性能和光学性质进行了测试。应用乍得-奥菲尔特（Judd-Ofelt）理论计算了Er^3＋离子的J-O理论参量和荧光寿命r。探讨了氟化物的引入对碲酸盐玻璃结构的改变的影响，并分析了其对玻璃的热学性质和光学性质的影响。实验发现，获得的氧氟碲酸盐玻璃具有优良的热学稳定性（△T=156.6C），宽的荧光半峰全宽（72nm）

掺铒碲酸盐玻璃的热力学稳定性和光谱性质的研究

分析了掺Er^3+碲酸盐玻璃的热力学稳定性能，研究了掺Er^3+碲酸盐玻璃的吸收和荧光光谱性质；应用Judd-Ofelt理论计算了碲酸盐玻璃中Er^3+离子的强度参数Ω(Ω2=4．79×10^-20cm^2,Ω4=1．52×10^-20cm^2，Ω6=0．66×10^-20cm^2)，计算了离子的自发跃迁几率，荧光分支比；应用McCumber理论计算了Er^3+的受激发射截面(σe=10．40×10^-21cm^2)、Er^3+离子^4I13／2→^4I15／2发射谱的荧光半高宽(FWHM=65．5nm)

一种新型掺铒碲酸盐玻璃的光谱性质研究

研究了一种新型掺Er^3+碲酸盐玻璃的光谱性质；应用Judd-Ofelt理论计算了碲酸盐玻璃中Er^3+离子的强度参数Ω(Ω2=4．79×10^-20cm^2，Ω4=1．52×10^-20cm^2，Ω6=0．66×10^-20cm^2)，计算了离子的自发跃迁概率，荧光分支比；应用McCumber理论计算了Er^3+的受激发射截面(σe=10．40×10^-21cm^2)，Er^3+离子^4I13/2→^4I15/2发射谱的荧光半高宽(FWHM=65．5nm)及各能级的荧光寿命(^4I13/2能级为τrad

Upconversion emissions in Yb3+-Tm3+-doped tellurite glasses excited at 976 nm

Intense Tm3+ blue upconversion emission has been observed in Tm3+-Yb3+ codoped oxyfluoride tellurite glass under excitation with a diode laser at 976 nm. Three emission bands centered at 475, 650 and 796 nm corresponding to the transitions (1)G(4) -> H-3(6), (1)G(4) -> H-3(4) and F-3(4) -> H-3(6), respectively, simultaneously occur. The dependence of upconversion intensities on Tm3+ ions concentration and excitation power are investigated. For fixed Yb2O3 concentrations of 5.0 mol%, the maximum upconversion intensity was obtained with Tm2O3 concentration of about 0.1 mol%. The blue upconversion luminescence lifetimes of the Tm3+ transitions (1)G(4) -> H-3(6) are measured. The results are evaluated by the possible upconversion mechanisms.

Spectroscopic properties of neodymium doped high silica glass and aluminum codoping effects on the enhancement of fluorescence emission

Nd3+ -codoped and Al3+-Nd3+-codoped high silica glasses have been prepared by sintering nanoporous glasses impregnated with Nd3+ stop and Al3+ ions. The Judd-Ofelt intensity parameters Omega(2,4,6) of Nd3+-doped high silica glasses were obtained and used to analyze aluminum codoping effects. Fluorescence properties of Nd3+-doped high silica glasses strongly depend on the Al3+ concentration. While Nd3+ ion absorption and emission intensities of obviously increase when aluminum is added to Nd3+-doped high silica glasses, fluorescence lifetimes decrease and aluminum codoping has almost no influence on the radiative quantum efficiencies. This indicates that aluminum codoping is responsible for an anti-quenching effect through a local modification of rare-earth environments rather than through physical cluster dispersion.

不同玻璃组分对掺铒碲酸盐玻璃 光谱性质的影响

Series of tellurite glasses were prepared by traditional melting method, the glass composition were changed and the different effects of glass modifier oxides(alkali metals and alkaline earth metal oxides) and glass intermediate (Y2O3, GeO2, Nb2O5, WO3) on the optical and spectroscopic properties of Er³⁺ doped tellurite glass were researched and compared. The infrared transmitting spectra, absorption spectra and fluorescence spectra were tested, the results showed that Nb2O5 and WO3 in the glass act as part of the body's role in the formation of the network, caused the reduction of transmitting range in infrared wavelength, which decrease the transmitting properties of tellurite glass. The introduction of high valence cationic ions, WO3 especially, can increase the FWHM of Er³⁺ for the increased polarization effect. With the decreasing of cationic field of glass modifier ions, the ion filed of the environment around Er³⁺ increased, subsequently, the role of ligand field polarization effect reduced, which makes the luminescence lifetime increase, and on the contrary the FWHM decrease monotonously.

Optical transitions and upconversion luminescence of Er3+/Yb3+-codoped halide modified tellurite glasses

Er3+-doped halide modified tellurite glasses were synthesized by conventional melting and quenching method. The Judd-Ofelt analysis was performed on the absorption spectra and the transition probabilities, excited state lifetimes, and the branching ratios were calculated and discussed. The intense infrared and visible fluorescence spectra under 980 nm excitation were obtained. Strong upconversion signal was observed at pumping power as low as 30 mW in the glasses with halide ions. The upconversion mechanisms and power dependent intensities were discussed, which showed two-photon process are involved for the green and red emissions. The decay times of the emitting states and the corresponding quantum efficiency were determined and explained. (C) 2004 American Institute of Physics.