Quantitative use of ultraviolet spectroscopy to calculate the effective irradiation dosage during weathering

The ultraviolet absorbance of a urethane coating showed typical yellowing that increased with exposure period. An effective dosage was calculated from the solar spectrum, the quantum yield for the degradation process and the ultraviolet absorption. Assuming a constant quantum yield, there is a clear acceleration of the absorption of damaging radiation because the ultraviolet absorption increases with exposure. This non-linear relationship offers possibilities on how to estimate a service lifetime. In addition, the yellowing can be analyzed as an “Urbach” tail which is usually attributed to structural disorder that introduces energy levels between the ground and excited electronic states.     

明胶大分子中的正电子湮没行为

The microstructural properties of gelatin samples derived from the bovine bone as well as skin of fish which inhabit in the cold sea were examined at molecular scale by using the positron annihilation lifetime spectroscopy（PALS）. The longest-lived component of PALS provides information about the free-volume holes in gelatin macromolecules. The results show that both average size and number of free-volume holes in the fish gelatin macromolecules are lower than those in the bovine gelatin macromolecules. Silver halide emulsions were also precipitated by using the balanced double-jet technique,for which two types of media containing fish gelatin and bone gelatin were used in the stage of nucleus formation,respectively. The monodispersibility of silver halide crystallites can be improved and the growth and coalescence of nucleus grains can be restricted when the fish gelatino-peptizer was used as dispersion medium at the nucleus formation. It thus suggested that the function of gelatino-peptizers as protective colloid is correlated with the microstructure character of gelatin macromolecules established by PALS. The gelatino-peptizer derived from the fish skin possesses stronger power governing nucleation and growth of silver halide grains compared with that made from the bovine bone.     

单电离态Kr原子强跃迁能级振子强度的研究

阐述了用束-箔方法通过测量单电离态Kr原子强跃迁谱线的能级寿命来 确定振子强度f-值的方法,并对确定出的强跃迁谱线的能级吸收振子强度进行简要讨 论。     

NO_2分子~2B_2电子激发态荧光辐射寿命的实验研究

采用准分子激光泵浦的染料激光诱导的高分辨荧光技术 ,测定了NO2 分子 A2 B2 电子激发态的荧光辐射寿命及其与激发波长、NO2 分子气体压力之间的关系 ,结果表明荧光衰减曲线是单指数的 ,辐射寿命在 2 0 .4 4～ 72 .53μs之间变化 ,利用光谱涨落统计理论对 A 2 B2 电子态的反常长寿命进行了讨论。     

掺镧PbWO4闪烁晶体的缺陷研究

利用正电子湮没寿命谱(PAT)和X射线电子能谱(XPS)研究了掺镧所引起的PbWO₄ 晶体缺陷的变化.结果表明：掺镧后,PbWO₄晶体中的正电子捕获中心铅空位(V< sub>Pb)浓度增加,并进一步诱导低价氧浓度的增加.讨论了掺La的作用机制,认为掺 La将抑制晶体中的氧空位,增加铅空位浓度. 关键词： 掺镧钨酸铅晶体 正电子湮没寿命谱 X射线电子能谱 缺陷     

时域两维荧光寿命显微测量研究

提出了一种新的时域两维荧光寿命显微测量技术,建立了一套荧光寿命成像显微系统,介绍了这种测量技术的数据处理方法。用标准样品对该系统进行了测试,实验表明,该系统的时间分辨率为2ps,在放大倍率为100倍的情况下,该系统的空间分辨率为8um。如果在现有的设备下采用更细的网格板和微位移系统,那么该系统的空间分辨率可小于1um.     

Fluorescence studies of the self‐organization of a cholesterol‐bearing polymethacrylate in n‐hexane solution

A copolymer of cholesteryl 6‐(methacryloyloxy)hexanoate and a small amount of (1‐pyrenylmethyl) 6‐(methacryloyloxy)hexanoate (Py‐C₅‐MA) was prepared by free radical copolymerization. A copolymer of 1‐eicosanylmethacrylate and a small amount of Py‐C₅‐MA was also prepared as a reference copolymer. A wide‐angle X‐ray diffraction pattern for an n‐hexane solution of the cholesterol(Chol)‐containing copolymer showed a peak corresponding to a spacing of 5.3 Å. In n‐hexane, the hydrodynamic radius (R_h) for the Chol‐containing copolymer (M_w = 7.8 × 10⁴) was 8.1 nm, while that of the eicosanyl‐containing copolymer (M_w = 4.9 × 10⁴) was 9.6 nm, R_h for the former being smaller than that for the latter, although M_w for the former was higher than that of the latter. ¹H‐NMR spectra of the Chol‐containing polymer in n‐hexane‐d₁₄ indicated a strong restriction of local motions of pendant Chol groups. Fluorescence spectra of the Chol‐containing copolymer in n‐hexane indicated that each pyrene group was isolated from others. In n‐hexane/benzene mixed solutions of the Chol‐containing polymer, the ratio of the intensity of the excimer relative to the monomer emission decreased with increasing the ratio of n‐hexane in the mixed solvent. Electron transfer from N,N‐dimethylaniline to singlet‐excited pyrene chromophores was suppressed in the Chol‐containing copolymer in n‐hexane. The pyrene chromophores exhibited a long triplet lifetime in n‐hexane. These observations led us to conclude that Chol groups formed stacks in n‐hexane, and that the pyrene chromophores were trapped in the Chol stacks, leading to the “protection” of pyrene from the bulk phase. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 47–58, 1999     

Hybrid Passivated Red Organic LEDs with Prolonged Operation and Storage Lifetime

In addition to mobile and TV displays, there is a trend of organic LEDs being applied in niche markets, such as microdisplays, automobile taillights, and photobiomodulation therapy. These applications mostly do not require to be flexible in form but need to have long operation lifetimes and storage lifespans. Using traditional glass encapsulation may not be able to fulfill the rigorous product specification, and a hybrid encapsulation method by combining glass and thin-film encapsulation will be the solution. Conventional thin-film encapsulation technology generally involves organic and inorganic multilayer films that are thick and have considerable stress. As a result, when subjected to extreme heat and stress, the film easily peels off. Herein, the water vapor transmission rate (WVTR) of a 2 µm silicon nitride film prepared at 85 °C is less than 5 × 10⁻⁵ g/m²/day and its stress is optimized to be 23 MPa. Red organic LEDs are passivated with the hybrid encapsulation, and the T₉₅ lifetime reaches nearly 10 years if the LED is continuously driven at an initial luminance of 1000 cd/m². In addition, a storage lifespan of over 17 years is achieved.     

荧光寿命测定的现代方法与应用

介绍了时间相关单光子计算、相调制和频闪等三种现代荧光寿命测定方法的工作原理,指出了各种方法的优点和局限性;介绍了时间相关单光子计数实验数据的处理方法;概述了时间分辨荧光技术在化学和生命科学中的应用。