伽玛射线暴与爱因斯坦相对论

伽玛射线暴(简称伽玛暴)是当今天体物理领域最热门的研究领域之一。继过去几年内长时标伽玛暴(持续时标长于2秒)研究取得的不断突破,2005年以来短时标伽玛暴(短于2秒)之谜也开始被解开,短暴的双中子星并合模型第一次得到观测支持。最近还发现一个红移高达6.3的伽玛暴,这标志着伽玛暴开始成为研究高红移宇宙学的探针。本文旨在对伽玛暴研究的历史和现状作一个回顾和评述,并就爱因斯坦所创立的相对论和宇宙学具体在伽玛暴研究中的应用作一些讨论。     

伽玛射线暴决定宇宙中出现生命的可能位置

在五十亿年以前,强烈的恒星爆发可导致地球生物大灭绝,并且也会抑制其他行星上产生生命。这样,生命只能于此后在星系的边际诞生。伽玛射线暴是恒星死亡时产生的强烈辐射,它可能伤害甚至消灭数光年外行星上的生命。两位天体物理学家分析了最新天文数据,重新估计了伽玛暴影响地球生命的可能性。他们发现,在过去十亿年内一颗伽玛暴导致生物灭绝的可能性达60%。望眼地球以外,他们还发现生命更趋向于在星系的边际出现,因为那里伽玛暴不常见。五十亿年以前,频繁的伽玛暴不利于宇宙中生命的形成。     

宇宙γ射线暴

 γ射线暴(以下简称γ暴)是来自宇宙空间的一种短时标的高能γ射线爆发现象。它的发现颇有戏剧性:60年代中期,为了监督关于禁止在大气层中进行核试验的条约的执行情况,美国发射了一些卫星,以监测核爆炸中的γ射线事件。1967年开始,Ｖｅｌａ卫星真的不时记录到一些γ射线爆发现象,使美国政府十分紧张。军方花了几年的时间终于搞清楚它们均来自于宇宙空间,证实只是一场虚惊。由于军事保密的原因,该现象直到1973年才由美国洛斯阿拉莫斯实验室的Ｋｌｅｂｅｓａｄｅｌ、Ｓｔｒｏｎｇ和Ｏｌｓｏｎ在ＡｐＪ(美国《天体物理杂志》)的一篇快报中以“对源自宇宙空间的γ射线爆发的观测”为题发表出来。     

X射线光电子能谱

X射线光电子能谱（X-ray photoelectron spectroscopy, XPS）技术也被称作用于化学分析的电子能谱（electron spectroscopy for chemical analysis,ESCA）.XPS属表面分析法,它可以给出固体样品表面所含的元素种类、化学组成以及有关的电子结构重要信息,在各种固体材料的基础研究和实际应用中起着重要的作用.文章简要介绍了XPS仪器的工作原理和分析方法,并给出了XPS在科学研究工作中的应用实例.     

X射线光电子能谱

X射线光电子能谱（X-ray photoelectron spectroscopy，XPS）技术也被称作用于化学分析的电子能谱（electron spectroscopy for chemical analysis，ESCA）．XPS属表面分析法，它可以给出固体样品表面所含的元素种类、化学组成以及有关的电子结构重要信息，在各种固体材料的基础研究和实际应用中起着重要的作用．文章简要介绍了XPS仪器的工作原理和分析方法，并给出了XPS在科学研究工作中的应用实例．     

羊八井宇宙线实验的现状和未来

概述了羊八井地理位置的物理优势和一期实验的显示性及其在日益激烈的国际竞争中面临的挑战和选择,提出了一个以RPC“地毯”、契仑可夫成像望远镜群和多成分复合阵列为手段,以亚甚高能天文、宇宙反质子流测量、太阳活动短期变化的监测研究及膝区物理的突破性攻关为目标的羊八井将来计划.     

硅片上超薄氧化硅层厚度测量的XPS标准曲线法

提出一种新的处理方法-XPS标准曲线法来测量硅片上超薄氧化硅层(SiO2/Si)的厚度。该方法利用一系列氧化硅厚度(d)准确已知的SiO2/Si标准样品,分别记录其氧化硅和元素硅的Si(2p)谱线,并得到峰高比(R),然后将厚度(d)对峰高比(R)作图得到标准曲线。在相同的实验条件下,测得未知样品氧化硅和元素硅的Si(2p)谱线并计算其峰高比,通过插入法在标准曲线上得到相应的氧化硅层厚度。SiO2/Si标准样品由设备一流和经验丰富的权威实验室提供,其氧化硅厚度采用多种方法进行测量比对。实验表明:基于氧化硅厚度准确知道的标准样品制作的XPS标准曲线,用于硅片上超薄氧化硅层厚度测量时具有快速、简便和比较准确等优点,有较好的实用价值。     

基于分段硬化曲线的X射线CT射束硬化校正方法

研究了X射线CT射束硬化的形成机理,分析了射束硬化校正的常用方法,建立了以投影灰度为自变量的射束硬化校正模型,从而降低了射束硬化校正的计算难度。分析了采用多项式拟合射束硬化曲线的优缺点,提出一种基于多项式的分段硬化曲线表达新方法。该方法首先采用过原点的多项式曲线拟合硬化数据,然后通过所得多项式曲线的曲率变化,判断该曲线在拟合区间两端是否出现振荡,并对振荡部分的多项式曲线采用幂函数曲线进行替换,同时保证各段曲线在连接点处C1连续(曲线的C1连续定义为, 两条曲线交于一点且在交点处的一阶导数相等)。计算机CT仿真实验结果表明,该方法对理想CT图像和含噪CT图像的射束硬化校正,均表现出良好的稳定性,并可基本消除射束硬化造成的伪影。     

纳米Cu固体材料的X射线衍射与正电子湮没研究

 采用自悬浮-冷压法,在不同压力下制得纳米Cu固体材料并对其在不同温度和保温时间下进行退火,利用X射线衍射(XRD)和正电子湮没寿命谱(PAS)分析对材料的结构和微观缺陷进行了表征。XRD分析表明,压制而得的样品晶粒度为20 nm,低于300 ℃退火3 h后并未发现晶粒显著长大;PAS分析表明,压制后的样品缺陷主要为单空位和空位团,大空隙很少,随着退火温度的升高和退火时间的延长,单空位通过扩散结合成空位团,大空隙也在温度较高时分解为空位团,导致空位团的含量增加,而单空位和大空隙的含量降低。     

纳米Cu固体材料的X射线衍射与正电子湮没研究

采用自悬浮-冷压法,在不同压力下制得纳米Cu固体材料并对其在不同温度和保温时间下进行退火,利用X射线衍射(XRD)和正电子湮没寿命谱(PAS)分析对材料的结构和微观缺陷进行了表征。XRD分析表明,压制而得的样品晶粒度为20 nm,低于300 ℃退火3 h后并未发现晶粒显著长大;PAS分析表明,压制后的样品缺陷主要为单空位和空位团,大空隙很少,随着退火温度的升高和退火时间的延长,单空位通过扩散结合成空位团,大空隙也在温度较高时分解为空位团,导致空位团的含量增加,而单空位和大空隙的含量降低。     

Relationship between width of pulses and Lorentz factor expected from the light curve of fireball sources

Time profiles of many gamma-ray bursts consist of distinct pulses, which provides a possibility of characterizing the temporal structure of these bursts. We employ a simple model of highly symmetric fireballs to analyse the effect of the expansion speed on the light curve arising from different forms of local pulses. The relationship between the ratio r of the FWHM width of the rising phase of the light curve to that of the decaying phase and the Lorentz factor is investigated. The analysis shows that, when the rest frame radiation form is ignored, temporal profiles of the light curve arising from pulses of fireballs will not be affected by the expansion speed （that is, r is almost a constant） as long as the fireball expands relativistically. When the rest frame radiation form is taken into account, there will be a break in the curves of r - log F. The location of the break depends mainly on the adopted value of the rest frame peak frequency VO,p. One would reach almost the same result when a jet is considered. In addition, we utilize a sample of 48 individual GRB pulses to check the relationship between the ratio r and the expansion speed F. We find no significant correlation between them, and this is consistent with the theoretical analysis.     

Development of the spectrum of gamma-ray burst pulses influenced by the intrinsic spectral evolution and the curvature effect

The spectral evolution of gamma-ray burst pulses assumed to arise from the emission of fireballs is explored. It is found that due to the curvature effect, the integrated flux is well related to peak energy by a power law in the decaying phase of pulses, where the index is about 3, which does not depend on intrinsic emission and the Lorentz factor. The spectra of pulses in the decaying phase are slightly different from each other when different intrinsic spectral evolution patterns are considered, indicating that it is dominated by the curvature effect. In the rising phase, the integrated flux keeps increasing whilst the peak energy remains unchanged when the intrinsic emission bears an unchanged spectrum. Within this phase, the flux decreases with the increase of the peak energy for a hard-to-soft intrinsic spectrum, and for a soft-to-hard-to-soft intrinsic spectrum, the flux generally increases with the increase of the peak energy. An intrinsic soft-to-hard-to-soft spectral evolution within a co-moving pulse would give rise to a pulse-like evolutionary curve for the peak energy.     

The delay time of gravitational wave – gamma-ray burst associations

The first gravitational wave (GW) – gamma-ray burst (GRB) association, GW170817/GRB 170817A, had an offset in time, with the GRB trigger time delayed by ~1.7 s with respect to the merger time of the GW signal. We generally discuss the astrophysical origin of the delay time, Δt, of GW-GRB associations within the context of compact binary coalescence (CBC) – short GRB (sGRB) associations and GW burst – long GRB (lGRB) associations. In general, the delay time should include three terms, the time to launch a clean (relativistic) jet, Δt_jet; the time for the jet to break out from the surrounding medium, Δt_bo; and the time for the jet to reach the energy dissipation and GRB emission site, Δt_GRB. For CBC-sGRB associations, Δtjet and Δt_bo are correlated, and the final delay can be from 10 ms to a few seconds. For GWB-lGRB associations, Δt_jet and Δt_bo are independent. The latter is at least ~10 s, so that Δt of these associations is at least this long. For certain jet launching mechanisms of lGRBs, Δt can be minutes or even hours long due to the extended engine waiting time to launch a jet. We discuss the cases of GW170817/GRB 170817A and GW150914/GW150914-GBM within this theoretical framework and suggest that the delay times of future GW/GRB associations will shed light into the jet launching mechanisms of GRBs.     

椭圆偏振光直接实验证的数据处理方法

从理论上分析了大学物理吉有关在椭圆偏振光实验里得不到椭圆曲线的原因,提出了得到椭圆曲线的数据处理方法。     

Properties of SN Ia progenitors from light curves and spectra

With recent advances in theory and observations, direct connections emerge between the progenitors of Type Ia Supernovae (SNe Ia) and the observed light curves and spectra. A direct link is important for our understanding of the supernovae physics, the diversity of SNe Ia and the use of SNe Ia for high-precision cosmology because the details of the explosion depends sensitively on the initial conditions and the explosion scenario(s) realized in nature. Do SNe Ia originate from SD- or DD systems, and do they lead to M_Ch mass explosions or dynamical mergers? Does the statistical distribtion of SNe Ia depend on their environment which can be expected to change with redshift? In this contribution, we will exam from the theoretical point of view the tell-tails for this connection, their consistency with the observations, and future directions. In a first section, we present the physics of the explosion, light curves and spectral formation in a nutshell to help understanding the connection. For details of the progenitor evolution and explosion physics, we refer to reviews and the other contributions in this issue. Each of the topical sections starts with a brief general review followed by a more detailed discussion of specific results. Because the youth of the field, some bias is unavoidable towards results obtained within our collaborations (and FSU). The imprint of the metallicity, progenitor stars and properties such as the central density of the exploding WD are presented. IR spectroscopy, polarimetry and imaging of SNR remnants are discussed as a tool to test for the WD properties, magnetic fields and asymmetries. We discuss different classes of Type Ia supernovae, and their environment. Possible correlations between the spectroscopic and light curve properties of SN Ia are discussed. Finally, the overall emerging picture and future developments are discussed.     

旋光晶体的寻常折射率与左旋光和右旋光折射率的关系

由光的波动方程证明,若介质为旋光物质,则其极化率张量χ一定有非对角对称的共轭虚元素,并导出了旋光晶体的寻常折射率no与左旋光折射率nL和右旋光折射率nR之间的关系.将理论分析结果与实验数据相对照,结果完全吻合.     

光强一定时饱和光电流随入射光频率的变化关系辨析

对光电效应实验中饱和光电流随入射光频率变化关系的几种谬误进行了辨析，给出了光强一定时饱和光电流随入射光频率变化的正确规律并作了解释。     

Third-order optical intensity correlation measurements of pseudo-thermal light

Third-order Hanbrury Brown–Twiss and double-slit interference experiments with a pseudo-thermal light are performed by recording intensities in single, double and triple optical paths, respectively. The experimental results verifies the theoretical prediction that the indispensable condition for achieving a interference pattern or ghost image in Nth-order intensity correlation measurements is the synchronous detection of the same light field by each reference detector, no matter the intensities recorded in one, or two, or N optical paths. It is shown that, when the reference detectors are scanned in the opposite directions, the visibility and resolution of the third-order spatial correlation function of thermal light is much better than that scanned in the same direction, but it is no use for obtaining the Nth-order interference pattern or ghost image in the thermal Nth-order interference or ghost imaging.     

利用色散补偿白光相关器及高通滤波技术检测粒子大小

本文提出了一种可用以检测相同形状粒子的大小、具色散补偿作用的白光相关系统,并完成了理论分析及实验验证.通过自动扫描光谱强度(位于固定点的相关峰的)分布,可方便地确定输入物的几何标度.本系统与高通滤波技术相结合,可检测圆环状粒子的大小,其相对误差的精度<2%.