二硫化碳自由基中间体的瞬态研究

用激光光解和脉冲辐解瞬态吸收光谱技术研究了二硫化碳(CS2)的光解和辐解反应机理及相应动力学特性。光解机理研究结果表明,CS2在308nm激光下生成激发三线态,该三线态与基态CS2反应产生自由基中间体,并测得了相关反应速率常数。应用脉冲辐解法进一步验证了光解中产生的CS2阴、阳离子自由基。研究结果为CS2对生物大分子的氧化性损伤假说提供了直接证据。     

乙腈体系中2′—萘乙酮激发三重态性质的激光光解研究

利用纳秒级激光光解瞬态光谱装置,以355nm激光为激光光源,二苯甲酮、周萘酮为光敏化剂和参比物,研究了2′－萘乙酯激发三重态在乙腈体系下激发三重态量子产额、单线态氧量子产额、激发态衰变反应动力学参数、氧淬灭反应速率常数、三重态摩尔光系数及二苯甲酮激发三重态与2′－萘乙酮之间的能量转移反应速率常数,并得到了2′－萘乙酮在乙腈体系中激发三重态瞬态吸收光谱。     

全反式视黄醛水包油微乳体系的激光闪光光解研究

以十二烷基磺酸钠为表面活性剂,环己烷为油相,正丁醇为助表面活性剂制备了全反式视黄醛（A11-transretinene,ATRN）的水包油微乳体系,然后利用355nm激光闪光光解技术,研究了微乳中ATRN的瞬态光化学性质。结果表明,ATRN经由355nm激光激发,生成ATRN激发三重态（^3ATRN＊）,^3ATRN＊的瞬态特征吸收波长为470mm。在酸性环境中,^3ATRN＊能与二苯胺发生电子转移反应,生成ATRN中性自由基和二苯胺阳离子自由基。通过研究^3ATRN＊与生物分子和抗氧化剂之间的反应表明：^3ATRN＊反应活性不高,由此推断ATRN可能经由光动力TypeⅡ途径,造成生物体系的光毒性。     

单线态氧引起的蛋白质损伤研究

在光敏剂参与下，生物组织经特定波长光辐照后产生的损伤或死亡称为光敏反应或光动力反应。光敏剂的激发态与基态氧发生激发能转移或电子转移产生单线态氧(^1O2)和超氧阴离子自由基(O^2-).^1O2是一种反应活性相当高的亲电瞬态中间体，能高效地氧化生物大分子，造成生物体的损伤。蛋白质分子是单线态氧氧化的主要靶分子之一。蛋白质中主要的发色基团有色氨酸、酪氨酸、苯丙氨酸、组氨酸、半胱氨酸、胱氨酸等，它们与单线态氧的反应受到普遍关注，以酪氨酸为例简要介绍如下：     

乙腈体系中2＇-萘乙酮激发三重态性质的激光光解研究

利用纳秒级激光光解瞬态光谱装置,以３５５ｎｍ激光为激发光源,二苯甲酮、周萘酮为光敏化剂和参比物,研究了２’－萘乙酮激发三重态在乙腈体系下激发三重态的量子产额、单线态氧量子产额、激发态衰变反应动力学参数、氧淬灭反应速率常数、三重态摩尔消光系数及二苯甲酮激发三重态与２’－萘乙酮之间的能量转移反应速率常数,并得到了２’－萘乙酮在乙腈体系中激发三重态的瞬态吸收光谱。     

阈能反应分子法激光分离铀同位素

论证了激光分离铀同位素阈能反应分子法在高浓铀小规模（10kg／a）生产中的可行性。提出了几种可能的阈能反应和对激光的要求，并指出电子静电加速器驱动的自由电子激光技术目前已有能力满足要求。     

光诱导4-硝基喹啉氧化物与甲硫氨酸衍生物的电子转移

利用纳秒级激光光解瞬态吸收光谱装置,研究了４－硝基喹啉氧化物（４ＮＱＯ）与含硫氨基酸及其肽的光化学反应。水溶液中的４ＮＱＯ被２４８ｎｍ激光激发,生成４ＮＱＯ三重态,并在４１０ｎｍ和５９０ｎｍ观察到它的特征吸收,４ＮＱＯ激发三重态能被甲硫氨酸及其肽猝灭,其过程是电子转移反应,生成４ＮＱＯ的加氢自由基和甲硫氨酸及其肽抽氧自由基。     

稀有三环核苷衍生物的光谱学研究

利用时间分辨激光光解技术对稀有三环核苷的前体化合物N - 4-desmethylwyosine(dYt)研究发现 ,该化合物能被 2 4 8nm激光单光子电离 ,但未观察到明显的激发三线态。用氧化性自由基SO4 · - 引发其阳离子自由基 ,揭示了其光电离机理。以KI溶液为参照 ,测得该化合物中性条件下的光电离量子产额 (Φe- )为 0 .0 4。     

丙酮三重态引发肽分子内电子转移的动态研究

运用ＫｒＦ激光不解瞬态上光谱、以丙酮为光敏剂研究了水溶液中色氨酰酷氨酸（Ｔｒｐ－－Ｔｙｒ）二肽的光化学过程，观察到丙酮三重态引发肽分子内的电子转移，由Ｔｒｐ／Ｎ·－Ｔｙｒ→Ｔｒｐ－Ｔｕｒ／Ｏ·自由基的生成过程。     

二元体系中激发分子反应对正子素(Ps)形成的影响

本文讨论了e~+云团中激发分子反应对Ps形成几率的影响,认为:(1)除了云团中的过剩电子之外,某些激发分子也可以对Ps的形成作出贡献;(2)激发分子与添加剂的反应也能影响Ps形成的几率,并且不同类型的反应(激发分子的猝灭或激发分子与添加剂分子之间发生电子转移)对Ps形成几率的影响也截然不同。根据云团反应的竞争机理,提出了Ps形成几率(三重态正子素O—Ps的几率I_3)与添加剂浓度之间的一般关系式(近似式),并用所得的关系式对一些典型的有机液体与CS_2,SF_6,C_2H_5Br,CCl_4等添加剂组成的混合体系进行了理论拟合,通过对拟合参数的分析,对一些“疑难问题”作出了明确的解释。并把添加剂的电子亲合势和激发分子的电离势等有机地联系了起来。     

Radiolysis of 2,2′-Azo-bis-isobutyronitriie in Benzene Solution, (II) Effects of Additives

The effect of additives on the radiolytic yield of nitrogen from the radiolysis of 2,2′-azo-bis-isobutyronitrile (AIBN) in benzene solution is examined. These additives have been known to quench excited benzene very effectively. Diacetyl, naphthalene, 2,5-diphenyloxazole (PPO) and anthracene with excitation energies lower than that of AIBN in the lowest triplet state decrease the nitrogen yield. The rate constants of these compounds in quenching the excited benzene are seen to be equal for both singlet and triplet states. An anomalously high quenching rate constant is seen for anthracene, which could be attributed to the quenching of high-lying excited state benzene.

Certain ketones with excitation energies higher than that of AIBN in the lowest triplet state also decrease the nitrogsn yield with the exception of benzophenone, these compounds are all seen to provide about the same degree of reduction in nitrogen yield, in the range of concentration studied. The rate constants of self-quenching and the average life of acetone and acetophenone have been determined from kinetic studies, and the results agree with that by other investigators.

The effect of several charge scavengers on the nitrogen yield are also reported.     

Interaction of excited molecules with macroradicals in the polymers under irradiation

The encounter complexes, which are formed in polystyrene (PS) and PS-based scintillators, combine the excimers and luminescent dopants with benzyl macroradicals known as efficient paramagnetic traps of excitation. The quenching of electronically excited states and dopants occurs via mechanisms other than energy transfer. The interaction of the radicals with excited molecules, which can be treated as a combination of migration and spin exchange in the encounter complex, results in an increase of the local concentration of triplet states in the radical neighborhood and the stabilizing of macroradicals primarily in the form of clusters. The radiolysis of these polymeric systems causes a space-correlated generation of macroradicals due to inhomogeneous structure of the polymers and specific interaction of the excited molecules with macroradicals. The efficiency of macroradicals as quenchers of the excited molecules depends not only on their concentration, but also on the character of their localizing in space. In other words, the efficiency will be lower with increasing the clusterization of macroradicals. The radiation resistance of the scintillators will be higher if macroradicals are stabilized in the form of clusters.     

On Rydberg series of autoionizing resonances

The calculation reported here is part of a general investigation of Δn = 0, 2 transitions between two Rydberg states in C²⁺ and Al⁹⁺. An intense laser is used to strongly couple the autoionizing state to another Rydberg state. The simulation uses Fano theory combined with the quantum defect method and the two-state model so as to reinforce the role of laser-induced degenerate state phenomenon on resonances obtained by laser. The calculation predicts a resonance parametrization in terms of Fano relative energy parameter and effective quantum number of the excited Rydberg state.     

激光光解研究焦脱镁叶绿酸-a作为光活化农药的可能性

利用激光光解时间分辨吸收方法，对蚕砂叶绿素中提取的焦脱镁叶绿酸-a的光化学性质进行了初步的研究。发现，该化合物在实验检测的波长范围内都有较强的吸收，且能产生较高量子产额的三重激发态。进而讨论它作为光活化农药的可能性。     

Electronic excitation in sputtered atoms and the oxygen effect

Bombardment of surfaces by ions gives rise to a variety of inelastic collision events leading to the ejection of excited atoms and ions. Such excited sputtered particles have been studied since more than 80 years through their optical emission, when they decay in front of the target to the electronic ground state, having lifetimes of 10⁻⁹ to 10⁻⁷ s, typically. Information on the energy distribution of such excited states can be obtained by two different techniques: light vs distance measurements (LvD) and by studying line profile broadening in light emission due to the Doppler effect. Only recently it has become possible to study in addition metastable excited atoms using laser induced fluorescence spectroscopy (LIF). Relative sputtering yields and energy distributions have been measured for such metastable states and two types can be distinguished. States with a very low excitation energy (0–0.3 eV), being sublevels of the electronic ground state, were found to have yields and energy distributions comparable to the electronic ground state, while metastable states at higher excitation energies (above 1 eV) seem to behave similar to short lived excited states, typically observed in secondary photon emission (BLE) with excitation energies in the range of 2–6 eV. This behaviour is also clearly visible with respect to oxygen surface coverage or increased near surface oxygen concentration where, similar to secondary ion emission, drastic changes in the yield by orders of magnitude have been found for excited atoms as well as for ions. In addition, under the same conditions a strong decrease in the sputtering yield of neutral ground state atoms has been observed for a number of metals. LIF results for highly excited metastable states are compared with recent results obtained by studying line profile broadening in light emission for Ca, Al and Cr targets. Different mechanisms that have been proposed to account for the observations will be discussed.     

Relative Population of the Levels of the 1s2s2p and 1s2p2 Configurations of Argon from Three Electron Excited Atoms

The possible contributions of the cascading from higher excited states to the states which can deexcite by the x-ray and Auger processes are investigated for Li-like argon. A model is developed to calculate the probability that a given excited state will eventually populate a particular lower excited state. The model requires the calculation of the transition rates of the cascading levels. Numerical results are presented for the cascade feeding of the levels of the ls2s2p and ls2p2 configurations. The cascading levels considered belong to the ls2snl and ls2pnl configurations with nl = 3s,3p,...4f.     

软X射线同步辐射光激励下表面吸附物质的选键解离与解吸

秀同步辐射X射线作为光源,可实现分子中某些原子芯能级的共振激发。而芯能级电子被共振激发到非占分子轨道后,其去激发过程通常以旁观者俄歇过程为主。由于在旁观者俄歇过程中被激发的电子在随后的去激发过程中并不参与,而是保留在具有反键特性的非占据轨道中,这样的分子激发态一般有较陡的排斥能面,所以它在紧随其后的离解与解吸过程中起着重要的作用。由于反键轨道一般定域在特定的化学键上,所以这一共振往往可引起分子中某些特定化学的断裂。这就象一把“化学剪刀”一样,它可将吸附在基底激发往往可引起分子中某些特定化学键的断裂。这就象一把“化学剪刀”一样,它可将吸附在基底表面吸附物质的某些碎片裁剪掉。通过芯能级共振激励离子解吸的实例,对其中的某些过程与机理进行探讨。     

Study on Vibrational Distribution of D2 Molecules in Edge Plasmas

The molecules‘s behavior in edge plasma is very important in understanding the phenomena near plasma-facing materials. In this paper, various processes of deuterium molecules are discussed and most recent data are applied in the evaluation of molecules‘ vibrational excitation. For the excitation of the molecules to triplet states, complete sets of vibrationally-resolved cross sections are not available from the literatures. Semi-classical Gryzinski method is used to calculate these cross sections and rate coefficients. Finally, The vibrational distribution of deuterium molecules is calculated by applying a quasi-steady state model for the balance of the vibrational populations. The dependence on the plasma parameters is discussed.     

核黄素(维生素B2)的光化学活性粒子:潜在的光生物学效应

应用３３７ｎｍ激光光解时间分辨吸收技术,通过考察核黄素（维生素Ｂ２）激发三重态的自猝灭及与酚类抗氧经剂的抽氢反应,核黄素阴离子自由基与氧气的电子转移反应,模拟了黄素在体内产生具有潜在光生物效应的活性粒子的途径,得到了一系列重要的动力学参数。为研究核黄素在体内的氧化还原作用,扩展它作为光敏化剂的用途提供了理论基础。