沉积物中石英ESR测年功率饱和效应的初步研究

介绍了几组沉积物中石英ESR功率饱和效应的基础实验情况,认为在用石英进行ESR测年时,微波功率的选择是一个重要参数,它直接影响累积剂量(AD)的求取,从而严重影响测年结果。在某些特定的地质环境下(如黄土,海洋沉积物),采用比较高的微波功率,可从沉积物石英的E＇心得到较老沉积物(大于50万年)可信的ESR年代。     

西德Bruker公司顺磁共振波谱仪微波功率调节方式的改进

在ESR研究中,精确的测量微波饱和功率点和其它一些研究工作,需要连续调节微波功率。目前Bruker的ESR谱仪的功率调节方式是以DB为单位,功率的变化是跳跃式的。根据该谱仪的原理,在没有更多的改变原电路基础上作者对微波功率的调节方式进行了改进。     

ESR波谱仪微波固体源的研制和测定电子自旋-晶格弛豫时间的简便方法

为了满足连续波饱和法测量顺磁场物质的电子自旋-晶格弛豫时间T₁对ESR波谱仪微波源的要求,制作了大功率、高稳定度的频带反射式外腔稳频耿氏振荡器,代替ESR波谱仪中较低功率的速调管源。     

运用ESR方法测定一些地质样品年龄的尝试

本文介绍了用ESR测地质年代方法的发展、现状及基本原理。给出了用ESR方法测定四川鲜水河地震活动断裂带的泉华样品、泥河湾的丽蚌化石样品、北京周口店洞穴中石笋样品的天然辐射总剂量AD的初步结果。测定周口店洞穴中石笋样品的年龄为(6×10⁴)年。并对结果进行了讨论。最后,还就有关ESR测年代方法的一些有关问题进行了探讨。     

利用夏皮罗台阶估算微波功率的方法及影响因素探究

将微波辐照到约瑟夫森结上,在结的电流电压(I-U)关系曲线中产生夏皮罗台阶。从0开始逐步增加微波功率到某一值,每一个微波功率和第0、1、2阶夏皮罗台阶高度组成的高度矩阵具有一一对应的关系。根据这个对应关系提出了一种估算微波功率的方法。在此研究基础上,分别利用电阻分流(RSJ)模型和电阻电容分流(RCSJ)模型研究约瑟夫森结中常态电阻和电容参量对夏皮罗台阶高度的影响,进而分析了结常态电阻和电容对微波功率估算精度的影响。     

碳酸盐沉积物的ESR断代

本文用ESR断代法测定某些碳酸盐沉积物的年代,其结果与¹⁴法符合得很好。对影响ESR断代法测定精度的一些因素进行了详细的讨论,如样品的处理、ESR测量、数据处理,年剂量和总累积剂量的测定。     

微波放电活化氮及氩与丙酮、丁酮反应机理的ESR/GC研究

用电子自旋共振(ESR)/气相色谱(GC)相结合的方法,研究了在氮或氧氢气存在下进行微波放电中酮类分子的反应过程.由ESR和GC平行检测结果表明:主要过程是经由微波放电面使N₂或Ar活化后形成激发态分子或激发态离子后,与酮分子进行碰撞传能而生成激发态酮分子,并立即进一步分解,继而产生自由基反应.     

采用正交光功率比值的光子型微波频率测量方案设计

通过构建两个正交的光功率比值,以光子技术实施微波频率测量.首先,待测微波信号经外调制器加载到连续光源上,在单边带载波抑制调制下仅得到单个光边带;以光学梳状滤波器对其进行滤波处理,在输出端检测得到随微波频率增大而呈现余弦函数和正弦函数变化趋势的两个光功率;将这两个光功率与参考光功率进行比较后,进而得到余弦函数型和正弦函数...     

论电子自旋共振技术

本文叙述了近十多年来电子自旋共振(ESR)技术的新发展和新动向,这种技术从1944年发现以来是连续不断改进的。从电子学方法方面,采用电子计算机处理ESR数据,固体微波源取代速调管,场效应管微波放大器取代量子放大器等技术上的改进,文中都进行了的简要叙述。由于磁共振理论的发展,对ESR灵敏度和分辨率的改善不仅用电子学方法,而且也用物理方法来提高。例如,对多重ESR技术,时间域ESR技术和三维图像技术都分别作了简短的评述。最后,本文作者对ESR技术今后发展的方向也作了预计,并提供了有关的参考文献。     

微波与热偏置下超导HEB太赫兹直接检测器的性能比较

本文介绍了一种基于超导氮化铌(NbN)热电子测辐射热计(HEB)的太赫兹(THz)直接检测器,并利用直流读出法和微波反射读出法,对微波与热偏置下HEB直接检测器的性能进行了比较.通过直流读出法,在最佳工作点处,测得微波偏置与热偏置条件下检测器的电流响应率分别为244A/W和20A/W,光学噪声等效功率(NEP)分别为4.5pW/√Hz和6.8pW/√Hz.相比于热偏置,微波偏置能够大大提高检测器的响应率.此外,我们利用微波反射读出法对微波偏置和热偏置下检测器的性能进行了比较.两种读出方式均可很好的表征检测器的性能,而相比于直流读出法,微波反射读出法更易于扩展到多像素阵列,同时具有很快的读出速度,对快速THz脉冲信号的检测具有重要意义.     

Testing the reliability of ESR dating of optically exposed buried quartz sediments

Optical dating of quartz by optically stimulated luminescence has a time range that is generally less than about 500 ka, due to relatively rapid saturation of the available luminescence defects in quartz. We test here a new method, electron spin resonance (ESR) optical dating of quartz, in which radiation-sensitive defects at aluminum and titanium atoms on silicon sites give rise to signals which can only be detected near liquid nitrogen temperature and which have a much higher capacity to absorb radiation dose before saturating than optical luminescence-detected signals. Our results show this method yields agreement with independent age control out to about 2.5 million years, extending here the dating range of optically exposed quartz in sediments in along-shore sediments (aeolian and waterlain) by a factor of about 5. Three sites in along-shore lacustrine and marine aeolian environments yielded very good agreement with independent age control. Details of single saturating exponential fitting in relation to agreement with expected burial doses and annealing of Al and Ti signals provide additional data to consider the best approaches to the dating method. Furthermore, we propose a new criterion for ESR optical dating: both the Al signal and Ti signal ages must agree to insure accurate burial ages. Moreover, when Al signal ages are lower than Ti signal ages, then the Al signal may be taken as the minimum burial age.     

Investigation on non-optically bleachable components of ESR aluminium signal in quartz

Electron Spin Resonance (ESR) can be used as a method to estimate the age of sediment deposition using the paramagnetic centre related to aluminium impurities in quartz. This so-called Al-centre can be partially optically bleached and its signal intensity decreases in relation to time exposure to solar light, until it reaches a plateau value corresponding to a residual signal. This signal can be attributed to “Deep Aluminium Traps” (DAT) which cannot be reset by an exposure to sunlight. In this study, we have investigated the behaviour of the DAT signal in samples from different origins and ages. The intensity of the DAT signal has been isolated from the total aluminium signal by the exposure of different quartz samples to simulated solar light. We observed that the DAT intensities were sample dependant and therefore it should be determined for each sample. Moreover, DAT intensities of Pleistocene volcanic quartz increase with gamma laboratory irradiation, whereas DAT intensities of sedimentary quartz do not vary with added artificial doses. This suggests that DAT in quartz extracted from sediments must be inherited from the primary source of the quartz, and were saturated at the time of sedimentation. We thereby validate the ESR dating of quartz sediment protocol used so far.     

Electron spin resonance characterization of calcretes from Thar desert for dating applications

Results of a study to characterize electron spin resonance (ESR) signals from naturally occurring carbonates from Thar desert are reported. Three radiation induced signals at g=2.0071 (signal A, very weak), g=2.0012 (signal B) and g=2.0003 (signal C) with linewidths ranging from 0.5–2 G are seen. A broad signal (BL) with linewidth 7 G is also seen at 2.0038. Detailed ESR experiments involving (1) sensitivity of ESR signals to ionizing radiation, (2) intensity variation of ESR signals with microwave power at different temperatures, (3) analysis of acid insoluble residue to estimate the interference from ESR signals of silicate fraction, and (4) X-ray diffraction analysis (to study possible phase changes on heating), led to the choice of signal BL for dating. Experiments on acid insoluble residue revealed that signal C has a contribution from the E′₁ centre of quartz and signal B is the parallel component (g_∥) of the E′₁ centre. Paleodose estimates based on signal BL are stratigraphically consistent.     

Exchange broadened,optically detected ESR spectra for luminescent donor-acceptor pairs in Li doped ZnO

Application of optically detected ESR to the yellow photoluminescence of Li doped ZnO gives ESR spectra for shallow donor - lithium acceptor pairs, showing that at least a fraction of the yellow emission is donor-acceptor (D-A) luminescence. The distribution of separations r_DA gives a spectrum of D-A exchange interactions J which broaden the ESR lines, particularly at high microwave power, where pairs with long excited state lifetimes, that is large r_DA, are power saturated.     

Nitrogen-Doped Chemical Vapour Deposited Diamond： a New Material for Room-Temperature Solid State Maser

Electron spin resonance （ESR） in polycrystalline diamond films grown by dc arc-jet and microwave plasma chemical vapour deposition is studied. The films with nitrogen impurity concentration up to 8 × 10^18 cm^-3 are also characterized by Raman, cathodoluminescence and optical absorption spectra. The ESR signal from P1 centre with g-factor of 2.0024 （nitrogen impurity atom occupying C site in diamond lattice） is found to exhibit an inversion with increasing the microwave power in an H102 resonator. The spin inversion effect could be of interest for further consideration of N-doped diamonds as a medium for masers operated at room temperature.     

微波电子自旋共振谱仪的调试

从实验操作者的角度，对微波电子自旋共振谱仪的原理及实验现象进行分析。     

ESR spectroscopic investigation of gamma-irradiated lithium trifluoromethanesulfonate

ABSTRACT

The effect of gamma radiation on lithium trifluoromethanesulfonate (LiTf) was investigated in detail using electron spin resonance (ESR) spectroscopy. The experimental spectra consisted of complex overlapped signals. Simulations of both the 1st- and 10th-day ESR spectra gave valuable information about the spectroscopic and structural features of radiation-induced radicals. More information about the qualitative and quantitative features of the radicals were gathered from the microwave power, storage time and dosimetric feature findings. In the light of the information obtained, four radicals were accepted to be produced after irradiation of LiTf.