强场中NO分子回归谱的长程散射矩阵的理论研究

采用半经典散射矩阵方法研究外磁场中高里德伯态双原子分子在能量范围为77010—77050cm^-1的回归谱.通过引进模型势简化强磁场中NO分子的高里德伯电子的势函数,找出其在核转动量子数分别为N=1,3,5的三个通道中的闭合轨道,重点分析了强磁场中NO分子的长程散射矩阵元实部的傅里叶变换谱与闭合轨道之间的一一对应关系.     

飞秒时间分辨拉曼光谱用于研究β-胡萝卜素单重激发态内转换和振动弛豫过程

搭建了飞秒时间分辨受激拉曼光谱(FSRS)装置，并用于研究全反式β-胡萝卜素单重电子激发态超快内转换和振动弛豫过程.基于三脉冲“抽运-探测”方案搭建的时间分辨受激拉曼光谱装置同时实现了150fs的时间分辨率和23.7cm^-1的光谱分辨率，光谱检测范围为300—4000cm^-1.对全反式β-胡萝卜素电子激发态的飞秒时间分辨拉曼光谱研究表明，β-胡萝卜素被激发到S₂态后，经由寿命约为0.3ps的中间态S_X态实     

“闪光二号”5 T脉冲强磁场装置

为了满足闪光二号加速器材料热力学效应研究的新需求,设计了一套电容器储能型脉冲强磁场装置。装置主要由储能电容器、半导体放电开关、磁场线圈及高压恒流充电源组成。磁场线圈中心处最大磁感应强度可达5 T,并且可以通过调整磁场线圈与二极管的相对位置实现磁透镜比的调节。通过理论计算和数值模拟相结合的方法对脉冲强磁场的关键参数进行了分析,然后进行了脉冲强磁场的工程设计,最后使用该强磁场装置进行了实验研究。强磁场实验中,当储能电容器充电21 kV时,在磁场线圈中心处获得了5.3 T脉冲强磁场。     

交叉偏振滤波技术提高飞秒超强激光信噪比的研究

对交叉偏振波滤波技术理论分析的基础上,在"极光-III"装置中采用该技术进行了钛宝石飞秒放大激光脉冲对比度提高的实验研究,不仅显著的抑制了纳秒范围内再生放大器产生的预脉冲,而且也将皮秒范围内的信噪比由10^-5提高到了10^-7,实验测得基波到交叉偏振波的转化效率大于10%.研究表明,该技术可以有效地提高飞秒超强激光的信噪比.     

飞秒光梳和碘稳频532nm Nd:YAG激光频率的测量

报道了中国计量科学研究院研制的基于掺钛蓝宝石(Ti:Sapphire)锁模飞秒脉冲激光器的飞秒光学频率梳装置，并利用此装置测量了碘稳频532nm(¹²⁷I₂R(56)32-10) Nd∶YAG固体激光器的频率，结果为 563260223512991±20Hz,相对不确定度为3.6×10^-14.这一数值是直接溯源到铯原子微波频率基准的光学频率测量结果.     

BFEL实现红外和X射线双波段运行的初步设计

 讨论了北京自由电子激光装置升级后实现红外和X射线双波段运行的主要物理和技术问题及其解决途径,并进行了初步设计。结果表明：红外自由电子激光器的波长调谐范围为4.9~16.8 μm,输出宏脉冲能量可达到50 mJ;背散射X射线光源可以覆盖0.45~3.49 keV能区,输出宏脉冲谱亮度为3.0×10²⁰ photons/(s·mm²·mrad²·0.1%BW),扩大了红外自由电子激光的应用范围,以及用户对相应能区X射线的应用需求。     

脉冲强磁场下的电极化测量系统

多铁性材料是当前物质科学研究的热点,具有重要的科学研究意义和应用前景.低温和强磁场实验环境为研究多铁性材料提供了一种有效途径.脉冲强磁场下的电极化测量系统能实现最高磁场强度60 T、最低温度0.5 K的铁电特性测量.该系统采用热释电方法,具有磁场强度高、控温范围广、转角测量等特点,可用于强磁场下的磁电特性研究.本文介绍了该系统的测量装置和实验原理,并展示了其在多铁性材料研究中的一系列应用,揭示了脉冲强磁场电极化测量系统在磁电特性探索中的重要作用.     

脉冲强磁场技术发展现状与趋势

脉冲强磁场是现代科学研究的重要工具,因其可以较容易地实现50 T以上磁场,因而在最近20年快速发展。最高磁场强度已经由70 T左右发展到目前的100 T,磁场波形也由以前单一的短脉冲发展到现在的长脉冲、平顶脉冲、长短合成脉冲等多种波形。随着电源与控制技术的发展,脉冲强磁场技术也在一定时间内实现了高稳定度磁场,拓宽了脉冲强磁场的实用范围;同时,脉冲磁体技术发展催生出能快速冷却的、具有高重频和异形结构的脉冲磁体,以满足X射线实验、中子实验和太赫兹实验要求。文章详细介绍了脉冲强磁场技术的发展现状与发展趋势,还介绍了武汉国家脉冲强磁场科学中心的磁场技术。     

近红外单光子探测器

该单光子探测器在实验中使用半导体制冷器制冷，雪崩二极管工作于盖革模式下，使用交流耦合方式提供门脉冲信号，通过延迟补偿和采样门控消除尖脉冲干扰，采用反馈门控减小后脉冲影响，优化电路参数减小暗计数.经实验测试与分析，温度在-62.5℃，门脉冲宽度为50ns，采样门控为10ns的条件下，最佳工作点的暗计数率小于4×10^-6ns^-1，量子效率约18%，噪声等效功率为2.4×10^-19W/Hz^1/2.     

基于交叉偏振波产生的脉冲净化技术研究与应用

本文利用交叉偏振波产生技术(XPW)对800 nm波段钛宝石飞秒激光器输出的激光脉冲进行时域净化, 提高脉冲时域对比度, 并测量验证了10¹¹对比度的脉冲, 达到测量仪器的动态范围极限, 比初始脉冲时域对比度有三个量级的提高, XPW的效率为22%. 同时发现净化后脉冲光谱宽度也得到一定展宽, 进一步利用啁啾镜对和补偿片对净化后的脉冲进行色散补偿, 得到25 fs脉宽的脉冲. 利用该净化后的激光脉冲作为种子注入已有的太瓦级钛宝石啁啾脉冲放大系统中, 在输出脉冲能量250 mJ, 宽度50 fs, 对应峰值功率5 TW的情况下, 在主脉冲前100 ps以外的范围内测量验证了10¹¹的脉冲对比度.     

Two-body beta decay of stored few-electron ions

The combination of the projectile fragment separator FRS and the cooler-storage ring ESR at the accelerator facility of GSI Darmstadt offers the unique opportunity to study beta decay of stored highly-charged ions. Basic nuclear properties such as masses and half-lives are measured by applying the mass- and time-resolved Schottky Mass Spectrometry (SMS). The relative mass-to-charge ratio is directly correlated to the relative revolution frequency. The SMS is sensitive to single stored ions and the decay of each stored ion can be precisely determine by steady monitoring of the corresponding revolution frequencies. On this basis the single particle decay-spectroscopy has been developed which allows for an unambiguous time-resolved and background-free identification of a certain decay branch. In this contribution we discuss experiments on the orbital electron capture (EC) of radioactive ions in the ESR. Fully ionized, hydrogen- and helium-like ¹⁴⁰Pr and ¹⁴²Pm ions have been selected for these studies. These nuclei decay to stable daughter nuclei via either the three-body ?? ^?+?- or the two-body EC-decay by a single allowed Gamow?CTeller (1^?+? ??0^?+?) transition.     

用电子自旋共振波谱研究ZnS:Mn结构相变的对数直线法

本文提出用电子自旋共振(ESR)波谱的对数直线法确定ZnS:Mn的结构相变温度,在研究微量掺杂离子影响ZnS微晶结构相变温度的实验分析中取得满意的结果,克服了X射线衍射对Mn²⁺浓度在10^-3—10^-6g/g范围内ZnS相变温度不能区分的困难。     

磷酸盐、氟磷酸盐和氟化物玻璃中过渡金属离子的顺磁共振研究(Ⅰ)——Cr3+,Mo3+

本文研究了磷酸盐、氟磷酸盐和氟化物玻璃中Cr³⁺的顺磁共振(以下简称ESR),从自旋哈密顿出发计算了Cr³⁺的有效g因子,指出低场谱线主要起源于两个Kramers双重态之间的跃迁,确定了自旋哈密顿参数:D=0.15—0.4cm^-1,E/D=0.15—0.3,零场分裂为0.3—0.8cm^-1,本文还报道了磷酸盐玻璃中Mo³⁺的ESR。 关键词：     

ESR study of the undoped heavy-fermion compound YbRh2Si2

The electron spin resonance (ESR) of the heavy-fermion metal YbRh₂Si₂ has been studied. The angular variation and the temperature dependence of the ESR line width have been measured in YbRh₂Si₂ single crystals in the temperature range of 4–25 K. The characteristic spin-fluctuation temperatureT ^* ～ 17 K estimated from these studies coincides very well with other experimental data. A well-behaved ESR signal due to local Yb³⁺ moments strongly supports the localized moment scenario for heavy-fermion quantum critical points.     

Development of Very-Low-Temperature Millimeter-Wave Electron-Spin-Resonance Measurement System

We report the development of a millimeter-wave electron-spin-resonance (ESR) measurement system at the University of Fukui using a ³He/⁴He dilution refrigerator to reach temperatures below 1 K. The system operates in the frequency range of 125–130 GHz, with a homodyne detection. A nuclear-magnetic-resonance (NMR) measurement system was also developed in this system as the extension for millimeter-wave ESR/NMR double magnetic-resonance (DoMR) experiments. Several types of Fabry–Pérot-type resonators (FPR) have been developed: A piezo actuator attached to an FPR enables an electric tuning of cavity frequency. A flat mirror of an FPR has been fabricated using a gold thin film aiming for DoMR. ESR signal was measured down to 0.09 K. Results of ESR measurements of an organic radical crystal and phosphorous-doped silicon are presented. The NMR signal from ¹H contained in the resonator is also detected successfully as a test for DoMR.     

Electron Spin Resonance–Native Signal in Thermally Treated Dental Tissue

Although the dosimetric Electron Spin Resonance (ESR) signal of hard tissues, particularly enamel, has been extensively studied, little attention has been paid to the native signal. This signal is known to be affected by the health of the tissue, as well as by socio–economic factors. In dental applications several clinical procedures, including the use of laser irradiation, can heat the tissue locally with side effects that must be studied. The purpose of the present work is to study the ESR signals in enamel and dentin tissues after thermal treatment with temperatures in the range of 100°C–300°C. Non‐irradiated permanent bovine teeth were studied. ESR measurements were performed with a Varian E‐4 ESR spectrometer operating in the X band range. Progressively larger ESR signals were produced in dentin tissues previously heat treated at and above 100°C. No detectable signals were observed in similarly treated enamel. The signal shows partial decay at four and six months after thermal treatment. The experimental data for dentin show a correlation with the Arrhenius function with an activation energy of (41 ± 2)10³ J/mol. After six months, the ESR signal shows a higher activation energy (67 ± 3)10³ J/mol and the decay shows a activation energy of (38 ± 2)10³ J/mol. A possible assignment of the signal origin in dentin is difficult. The water lost during thermal treatment and reincorporated during the following six months correlates with the signal gain and subsequent decay. The water lost can produce point defects in the hydroxyapatite, or structural changes in the collagen structure. The results observed here are useful for understanding the thermal effects produced in dentin by infrared laser irradiation, and provides a cautionary warning that annealing conditions in ESR studies of biological tissues should be standardized.     

Radiative heating of thin Al foils by intense extreme ultraviolet radiation

The effect of induced transparency of thin Al foils radiatively heated by intense extreme ultraviolet (EVU) radiation has been observed. The radiation of the plasma of Z-pinches appearing under the compression of tungsten liners at the Angara-5-1 facility has been used as the radiation that heats the Al foil (peak illumination on the foil ~0.55 TW/cm²) and is transmitted through it. The photoabsorption has been studied in the formed aluminum plasma at temperatures of ~10–30 eV in the density range of ~1–20 mg/cm³ in the wavelength range of ~5–24 nm. Absorption lines of Al^4+...7+ ions have been identified in the experimental spectrum. In addition, radiative gas-dynamic simulations of the foil heating and expansion have been performed taking into account radiation transfer processes.     

Low-Temperature Phase Transition Detected by ESR in ����-(BEDT-TTF)2IBr2 Single Crystals

Hysteresis of the electron spin resonance (ESR) spectra of localized charge carriers has been observed in ????-(BEDT-TTF)₂IBr₂ single crystals in the temperature range of 15?C30?K. The first-order phase transition has been detected by ESR components. Two lines observed in the ESR spectrum correspond to low-temperature and high-temperature phases.     

A new experimental approach for isochronous mass measurements of short-lived exotic nuclei with the FRS-ESR facility

Projectile fragments separated in flight with the FRS have been injected into the storage ring ESR. Operating the ESR in the isochronous mode has enabled high-resolution mass measurements of short-lived isotopes. Already in our pilot experiments the Isochronous Mass Spectrometry (IMS) has provided accurate results for a restricted isotope range in the neighborhood of a selected isotope characterized by the best isochronous condition. In the present experiment this restriction has been overcome by precise external magnetic rigidity determination (1.5·10^–4) at the dispersive midplane of the FRS. In this way the mass resolving power for neutron-rich fission fragments covering a large mass-over-charge ratio in one spectrum has been improved by up to one order of magnitude and the accuracy by more than a factor of two.     

Optically Detected ESR (OD ESR) of ion-radical Pairs in coloured solutions. Observation of transienttrans-azobenzene radical cation

Trans-azobenzene dissolved in different liquid hydrocarbons absorbs fluorescence arising from all acceptors previously used in Fluorescence Detected Magnetic Resonance (FDMR) and Optically Detected ESR (OD ESR) spectroscopy making optical detection impossible. In this report a new acceptor,rubrene, having sufficient quantum yield of fluorescence in the red band 550–620 nm, has been proven successful. OD ESR spectra of the radical-ion pairtrans-azobenzene⁺/rubrene^? were detected in liquid squalane (2,6,10,15,19,23-hexamethyl-tetracosane) solution in the temperature range 294–243 K. The experimental isotropic hyperfine splittings of the radical cation oftrans-azobenzene (a _N=1.4 mT) have been compared with those from MNDO/INDO calculations and with those of earlier work using freon matrix studies.