NCl(a1Δ)/I（2P3/2）传能体系的实验研究

 利用微波放电Cl₂/He等离子体作为Cl源，对反应NCl(a¹Δ) + I(²P_3/2)→NCl(X³Σ) + I(²P_1/2)进行了实验研究，得到了较大的I(²P_1/2)自发辐射荧光信号，检测到NCl(a¹Δ，b¹Σ)自发辐射荧光光谱在存在少量I(²P_1/2)下发生的显著变化，其中NCl(a¹Δ)自发辐射荧光信号降低，同时由于I(²P_1/2)的作用，NCl(b¹Σ)自发辐射荧光信号大幅度增加。在考察各反应气体流量对I(²P_1/2)自发辐射荧光信号的影响时发现，在本次实验条件下，各种气体的最佳流量：He为1～4mmol/s, I₂为0.01～0.03mmol/s, Cl₂为1.0mmol/s左右,而HN₃流量略大于Cl₂流量时信号升高幅度开始变缓，约为Cl₂流量的两倍时信号不再有显著的变化。     

Effective ionization coefficients and electron drift velocities in gasmixtures of CF3I with N2 and CO2 obtained from Boltzmannequation analysis

The electron swarm parameters including the density-normalized effective ionization coefficients (α-η)/N and the electron drift velocities V_e are calculated for the gas mixture of CF₃I with N₂ and CO₂ by solving the Boltzmann equation in the condition of steady-state Townsend (SST) experiment. The overall density-reduced electric field strength is from 100 Td to 1000 Td (1 Td=10^-17 V·cm²), while the CF₃I content k in the gas mixture can be varied over the range from 0% to 100%. From the variation of (α-η)/N with the CF₃I mixture ratio k, the limiting field strength (E/N)_lim for each CF₃I concentration is derived. It is found that for the mixtures with 70% CF₃I, the values of (E/N)_lim are essentially the same as that for pure SF₆. Additionally, the global warming potential (GWP) and the liquefaction temperature of the gas mixtures are also taken into account to evaluate the possibility of applying in the gas insulation of power equipment.     

Excitation and dissociation of polyatomic molecules under the action of femtosecond infrared laser pulses

The effect of high-intensity femtosecond laser pulses (100–200 fs) in the near (0.8–1.8 μm) and medium (4.6–5.8 μm) IR ranges on the CF₂HCl, CF₃H, (CF₃)₂C=C=O, and C₄F₉COI molecules is examined. Irradiation of CF₂HCl and CF₃H molecules by 0.8-to 1.8-μm laser pulses with intensities of >40 TW/cm² (>4 × 10¹³ W/cm²) makes them dissociate to yield CF₃H and CF₄, respectively. The key mechanism of the dissociation of these molecules is field ionization and fragmentation. The excitation of the stretching vibrations of the C=O bond in the (CF₃)₂C=C=O and C₄F₉COI molecules by 4.5-to 5.8-μm femtosecond pulses produced no detectable dissociation up to a fluence of ∼0.5 J/cm² (or a intensity of ∼2.5 TW/cm²). Probable explanations of this observation are discussed. Original Russian Text ? V.M. Apatin, V.O. Kompanets, V.B. Laptev, Yu.A. Matveets, E.A. Ryabov, S.V. Chekalin, V.S. Letokhov, 2007, published in Khimicheskaya Fizika, 2007, Vol. 26, No. 4, pp. 18–25.     

离子速度成像系统校准及1,4-氯溴丁烷的紫外光解动力学

大气臭氧层破坏越来越严重, 卤代烷烃在太阳紫外线辐射下解离生成破坏臭氧的游离态卤素原子, 是主要元凶之一. 本文选用碘甲烷作为校准分子, 利用离子速度成像技术和共振增强多光子电离技术测得碘甲烷在266 nm紫外光解离下产生的基态碘原子I(²P_3/2)在不同聚焦电压下的离子速度影像, 得到离子速度成像系统的放大系数N=1.13. 并利用该系统研究了1, 4-氯溴丁烷在～ 234 nm紫外辐射下的解离动力学, 分析讨论了解离产生的基态Br (²P_3/2)和激发态Br^* (²P_1/2)的速度和角度分布信息, 揭示了1, 4-氯溴丁烷在～ 234 nm紫外光解离产生基态Br原子和激发态Br^* 原子的通道都是源于C-Br键排斥势能面上的快速解离. 文中通过计算碎片影像角度分布的各项异性参数β值, 得到了生成基态Br(²P_3/2)和激发态Br^* (²P_1/2) 两个解离通道中的平行跃迁和垂直跃迁比例. 另外, 本文还对氯溴甲烷, 1, 2-氯溴乙烷, 1, 3-氯溴丙烷和1, 4-氯溴丁烷在～ 234 nm下的光解动力学进行比较, 分析得到双卤代烷烃分子解离机理对烷基支链长度的依赖关系.     

THE 82S1/2→62D EXCITATION TRANSFER OF RUBIDIUM ATOMS INDUCED BY COLLISIONS WITH GROUND-STATE RUBIDIUM AND HYDROGEN MOLECULES

The processes of excitation transfer from the 8²S_1/2 state to the 6²D state of rubidium in Rb(8²S_1/2)-Rb(5²S_1/2) and Rb(8²S_1/2)-H₂ collisions have been studied experimentally. During irradiating the Rb vapor, mixed with H₂, by two light beams for selective stepwise excitation, the Rb 8²S_1/2→5²P_3/2 direct fluorescence and the Rb 6²D_3/2→5²P_1/2 sensitized fluorescence have been measured as a function of H₂ gas pressure. The measurements yielded the cross-sections σ(8²S_1/2→6²D) and σ^*(8²S_1/2→6²D) of Rb 8²S_1/2→6²D excitation tranfer induced by collisions with 5²S_1/2 atom and H₂ molecules respectively. The results are discussed in detail.     

THE 82S1/2→62D EXCITATION TRANSFER OF RUBIDIUM ATOMS INDUCED BY COLLISIONS WITH GROUND-STATE RUBIDIUM AND HYDROGEN MOLECULES

The processes of excitation transfer from the 8²S_1/2 state to the 6²D state of rubidium in Rb(8²S_1/2)-Rb(5²S_1/2) and Rb(8²S_1/2)-H₂ collisions have been studied experimentally. During irradiating the Rb vapor, mixed with H₂, by two light beams for selective stepwise excitation, the Rb 8²S_1/2→5²P_3/2 direct fluorescence and the Rb 6²D_3/2→5²P_1/2 sensitized fluorescence have been measured as a function of H₂ gas pressure. The measurements yielded the cross-sections σ(8²S_1/2→6²D) and σ^*(8²S_1/2→6²D) of Rb 8²S_1/2→6²D excitation tranfer induced by collisions with 5²S_1/2 atom and H₂ molecules respectively. The results are discussed in detail.     

晶体电光和非线性光学效应的离子基团理论(Ⅱ)——利用(IO3)-1离子基团的分子轨道计算α-LiIO3晶体的倍频系数

本文对碘酸盐晶体的倍频效应提出了一个(IO₃)^-1离子基团模型,并用(IO₃)^-1离子基团的分子轨道计算了α-LiIO₃的倍频系数,计算值和实验值符合得很好。由此得出以下结论:碘酸盐晶体的倍频效应主要由(IO₃)^-1离子基团和它的共价键轨道所决定。而在(IO₃)^-1离子基团中,对倍频效应作出主要贡献的是碘的孤对电子轨道和氧的|2σ>,|2P_y>轨道。     

用云母弯晶谱仪探测Z箍缩等离子体X射线光谱

 为了研究Z箍缩等离子体辐射的X射线光谱,研制了可用于“阳”加速器上探测宽频谱范围的X射线椭圆弯曲晶体谱仪。该谱仪晶体分析器采用云母材料,椭圆焦距为1 350 mm,离心率为0.948 5,覆盖布拉格范围为30°~60°,可探测X射线波长范围为0.10~1.73 nm(0.86~1.00 nm除外),用X射线胶片接收光谱信号。探测实验在中国工程物理研究院“阳”加速器上进行,实验结果表明:谱仪获取了氩的类氢共振线L_ya及其伴线、类氦共振线(1s2p¹P₁-1s2¹S₀)w线及磁四级M₂2跃迁(1s2p³P₂-1s²¹S₀)x线、互组合跃迁(1s2p³P₁-1s²¹S­₀)y线、禁戒谱线(1s2p³S₁-1s²¹S₀)z线和K­_-a线,谱线分辨率达到564。实验证明弯晶谱仪适合于Z箍缩等离子体X射线光谱学诊断。     

Cl+HN3产生NCl(a1Δ)和NCl(b1∑)的实验研究

 对利用微波放电直接解离Cl₂生成Cl, Cl与HN₃反应生成NCl(a^1Δ )和NCl(b^1∑)的过程进行了实验研究。得到了较强的NCl(a^1Δ 和NCl(b^1∑)自发辐射光谱,考察了Cl₂流量和He/Cl₂配比对NCl(a^1Δ 和NCl(b^1∑)生成的影响。发现对于一定的He流量,Cl₂流量对NCl(a^1Δ 和NCl(b^1∑)生成的影响存在一最佳范围,而最佳He/Cl₂配比不是一定值,而是随He流量升高而变大,在实验所考察的He流量范围（5~40 L/min）内,最佳He/Cl ₂配比在30∶1~100∶1之间。     

OCS分子在128 nm附近的光解动力学研究：S(3PJ=2,1,0)、S(1D2)以及S(1S0)产物通道

本文利用时间切片离子成像技术对OCS分子进行了真空紫外波段的光解动力学研究. 在四个光解光波长(从129.32到126.08 nm)下测量了硫原子解离产物S(³P_J=2,1,0)、S(¹D₂)、S(¹S₀)的速度影像，并从中清晰地发现了四个主要的解离产物通道：S(³P_J=2,1,0)+CO(X¹Σ⁺)，S(³P_J=2,1,0)+CO(A³π)，S(¹D₂)+CO(X¹Σ⁺)和S(¹S₀)+CO(X¹Σ⁺). 在实验影像中，产物CO分子的部分振动态结构能够得到分辨. 实验还获取解离产物总平动能谱，产物分支比和角分布. 对实验结果进行分析显示除绝热解离通道S(³P_J=2,1,0)+CO(A³π)之外，在其他三个产物通道中非绝热效应都起到非常重要的作用.     

Possibility of separating the isotopes127I and129I with the aid of a photodissociation iodine laser

A method for separating iodine isotopes is proposed, based on the large difference between the rate constants of the excited I*(²P_1/2) and unaxclted iodine atoms with radicals CF₃ and with Cl₂ molecules, and on the possibility of selectively acting on the₁₂₇I atoms in the states²P_1/2 and²P_3/2 by radiation from a photodissociation R¹²⁷I iodine laser (λ = 1.315 μm). The possibility of separating the pure isotope¹²⁹I and the mixture¹²⁷I with¹²⁹I is investigated.     

Experimental study on the system of Cl/Cl_2/He/HN_3/I_2

Using a microwave generator, chlorine diluted by helium was dissociated to chlorine atoms that subsequently reacted with hydrogen azide to produce the excited states of NCl(a1△). Meanwhile, molecular iodine with carrier gas of helium reacted with atomic chlorine to produce atomic iodine which then was pumped to excited state of I(2P1/2) by an energy transfer reaction from NCl(a1△). In this paper, the changes of NCl(a1△) and NCl(b1∑) emission intensity is presented when I2/He is introduced into the stream of Cl/Cl2/He/HN3/NCl(a1△)/NCl(b1∑). The dependences of atomic iodine I(2P1/2) on flow rates of gases were also investigated. The optimum parameters for I(2P1/2) production are given.     

紫外波段CH2I2分子的光解离动力学研究

利用离子速度成像方法,研究CH2I2分子在277—305nm范围内若干波长处的光解离动力学.通过同一束激光经(2+1)共振多光子电离(REMPI)过程探测光解碎片I(2P32)和I(2P12),得到了不同激发波长处的离子速度分布图像,从而获得CH2I2光解产物的能量分配和角分布.实验发现,碎片CH2I自由基有很高的内能激发,约占总可资用能的80%,该能量分配可以较好地用冲击模型来解释.实验还发现,产物I(2P32)和I(2P12)具有很不相同的平动能分布,结合所得到的碎片能量分配和角分布,我们对碎片I(2P32)和I(2P12)生成机理进行了分析,指出CH2I2分子电子激发态的绝热和非绝热解离决定了碎片的平动能分布. 关键词： CH2I2 离子速度成像 绝热和非绝热解离     

CF4/Ar微波放电与CS2反应的可见化学发光研究

利用交叉分子束-化学发光研究方法,研究了气相条件下不同反应压力时CF4／Ar微波放电的产物与二硫化碳CS的交叉反应在可见区(300～900nm)的化学发光,利用密度泛函B3LYP和二阶微扰MP2理论分别在6-311 G(3df,2pd)和6-311 G(d,p)基组下计算了可能的反应产物电子基态的构型和振动频率,将得到的光谱标识为F2S2电子激发态的发射谱,通过对光谱和产物的分析,认为微波放电得到的亚稳态的Ar原子与CS发生碰撞反应使CS解离为S原子和CS,解离得到的S原子与微波放电产生的F原子发生多步反应得到了F2S2的激发态。     

外电场作用下CF_3I分子结构特性及性质

CF_3I由于其良好的绝缘性能和较低的液化温度而作为SF_6替代性气体被广泛研究.本文采用量子化学从头计算法在3-21g基组下优化了CF_3I基态分子结构,得到了基态CF_3I分子的键长、分子前线轨道、Mulliken电荷布居数、红外光谱等.并且在此基础上采用杂化CIS/3-21g方法计算了分子的激发态,得到了分子的激发能、波长和振子强度.结果显示基态CF_3I分子在外电场作用下分子结构发生形变,分子能隙减小,分子活性变强;分子前9个激发态变化明显,随着外电场强度增加,第1、2、9激发能先增大后减小,第3、4、5、6、7与8激发能逐渐减小;第1、2、9激发波长先减小后增大,3、4、5、6、7与8激发波长逐渐增大;在0～0.009 a.u.外电场作用下,第1、2、4、5、6激发态振子强度为零,属于禁阻跃迁,第3、9激发态振子强度随着电场强度的增加而减小,第7、8激发态振子强度随着外电场强度的增加而增加.     

Er：YLF晶体中Er^3＋离子的光谱特征

利用居地－奥非脱（Ｊｕｄｄ－Ｏｆｅｌｔ）理论计算了Ｅｒ＾３＋离了在氟化钇锂（ＬｉＹＦ４简写为ＹＬＦ）晶体中的辐射跃迁几率Ａｊｊ无辐射跃迁几率ωＪＪ及激发态荧光寿命τ，并根据荧光动力学方程计算出各激发态布居数ＮＪ与掺杂浓度ｘ的关系，对２．７μｍ激光（＾４Ｉ１１／２→＾４Ｉ１３／２）来说，掺杂浓度要大于～３ａｔ％，才能实现布居数反转，对波长为１．７３μｍ的＾４Ｉ１３／２→＾４Ｉ１５／２跃迁，存在荧光强     

Reactions of excited I*(2P1/2) and unexcited I(2P3/2) iodine atoms in perfluoroalkyl radicals

A method of investigating reactions of excited and unexcited atoms is discussed. It is based on pulsed photolysis of molecules with simultaneous passage of laser radiation through the working medium. The method proposed is used to investigate the reactions that accompany the photolysis of the molecules RI(CF₃I, n-C₃F₇I, i-C₃F₇I). The rate constants of the recombination of iodine atoms into I₂ in the presence of RI molecules are calculated for the atoms I(²P_3/2) and I*(²P_1/2), as are the recombination constants of the radicals R into R₂ and with the atoms I*(²P_1/2) and I(²P_3/2) into the RI molecule. It is shown that the I(²P_3/2) atoms are much more active in the recombination into Ia and RI than the I*(²P_1/2) atoms. The role of the investigated reactions in the kinetics of a photodissociation iodine laser (PDIL) is discussed. The results are compared with the published data.     

Cs_2(B~1Π_u)态与基态Cs原子间的碰撞激发转移

在Cs2密度约为2×1013 cm-3的纯Cs样品池中,脉冲激光激发Cs2(X1 Σg+)至B 1Πu态,利用原子和分子荧光光谱方法研究了Cs2(B 1Πu)+Cs(6S)的碰撞激发转移过程.用736 nm激发Cs2到B 1Πu(v＜10),这时预解离不发生.由B 1Πu→X1 Σg+时间分辨跃迁信号得到B 1Πu态的辐射寿命为(35±7)ns,B1Πu态与Cs原子碰撞转移总截面为(4.0±0.5)×10-14 cm2.用705 nm激发至B 1Πu(v＞30)态,这时发生预解离,在不同的Cs密度下,测量了I(D1),I(D2)和分子带的时间积分荧光的相对强度,得到了预解离率为(4.3±1.7)×105 s-1(对预解离到6P3/2)和(4.7±1.9)×106 s-1(对预解离至6P1/2);碰撞转移截面为(0.45±0.18)×10-14 cm2(对转移到6 P1/2)和(4.3±1.7)×10-14 cm2(对转移到6P3/2).结果表明,如果B 1Πu(v)是束缚的,6P原子由碰撞转移产生;如果B 1Πu(v)是预解离的,则6P原子由预解离和碰撞转移产生.     

Multiphoton ionization of iodine atoms and CF<Subscript> 3</Subscript>I molecules by XeCl laser radiation

We report about effective ionization of iodine atoms and CF₃I molecules under the action of intense XeCl laser radiation (308 nm). The only ion fragment resulting from the irradiation of the CF₃I molecules is the I⁺ ion. We have studied the influence of the intensity, spectral composition, and polarization of the laser radiation used on the intensity of the ion signal and the shape of its time-of-flight peak. Based on the analysis of the results obtained, we have suggested the mechanism of this effect. The conclusion drawn is that the ionization of the iodine atoms by the ordinary XeCl laser with a nonselective cavity results from a three- (2 + 1)-photon REMPI process. This process is in turn due to the presence of accidental two-photon resonances between various spectral components of the laser radiation and the corresponding intermediate excited states of the iodine atom. The probability of ionization of the atoms from their ground state I(²P_3/2) by the radiation of the ordinary XeCl laser is more than two orders of magnitude higher than the probability of their ionization from the metastable state I^*(²P_1/2). The ionization of the CF₃I molecules by the XeCl laser radiation occurs as a result of a four-photon process involving the preliminary one-photon dissociation of these molecules and the subsequent (2 + 1)-photon REMPI of the resultant neutral iodine atoms.     

激发态Cs2和H2的电子-振转能级的碰撞转移

利用相干反斯托克斯拉曼光谱(CARS)探测技术, 研究了激发态Cs2与H2间的电子-振转能级的碰撞转移。用波长为532 nm和中心波长为716 nm的两束激光同时聚焦到样品池中, 扫描CARS谱确认了H2分子的S支(△v =1, △J=2)仅在v=1, J=4,5及v=2, J=3,4能级上有布居, 用n1、n2、n3、n4分别表示(2,4)、(2,3)、(1,4)及(1,5)上的粒子数密度。从CARS线的峰值得到n2/n1、n3/n1、n4/n1分别为6.34±1.27、3.66±0.73和1.45±0.29。转移能配置到振动、转动和平动的比例分别为0.44、0.06和0.50, 能量主要分配在振动和平动上。在T=523 K和PH2=2.5×103 Pa条件下, 通过求解速率方程组和对时间分辨CARS线轮廓的分析, 得到碰撞转移速率系数k1=(6.0±1.2)×10-14 cm-3s-1和k2=(4.0±0.8)×10-13cm-3 s-1。