TEA CO_2激光激励UF_6和H_2反应

在温度为20—23℃、UF_6分压为16托(UF_6:H_2～1:8)、激光波长10.59微米、能量为～1焦耳条件下,研究了激光激励UF_6和H_2反应。当激光聚焦于反应室时,观察到从焦点区发出的强烈兰光(焦点区能量密度为～10~2焦耳/厘米~2)。同时产生明显的压力下降现象和灰白色固体产物,红外光谱分析表明:在激光辐照300个脉冲后反应室中的 UF_6全部消失,同时伴有 HF 产生。从反应后的压力下降值证实了激光诱导介质击穿UF_6和H_2反应按2UF_6+H_2=2UF_5↓+2HF 式进行的可能性较大。     

用16微米激光进行UF_6的多光子离解实验研究

在温度为18°—20℃、UF_6压力为1托、H_2压力为2.5托、CF_4激光波长16.25微米、脉冲能量为5—25毫焦耳、脉宽为160毫微秒、重复率为0.33赫/秒、焦点区能量密度为0.5—2.5焦耳/厘米~2条件下,完成了UF_6单频多光子离解过程。离解阈值为～1焦耳/厘米~2。聚焦体积内分子分解几率为16～25%。从InSb红外探测器接收到的2.8微米荧光信息表明:反应过程中有振动热 HF~*分子产生。荧光脉冲在激光脉冲尖峰内迅速产生。反应按 UF_6■UF_5+F,F+H_2→HF+H 式进行的可能性较大。     

红外激光表面化学反应的初步研究

催化剂能降低化学反应的活化能从而提高反应速率,对反应途径有特殊的选择性。本文研究了二氧化碳激光器产生的红外激光对 NH_3和 SF_6在热金属丝表面上分解反应的影响,以及 TEACO_2激光单脉冲诱发的 NH_3一O_2复相爆炸反应。在 NH_3体系的实验中,使 CW CO_2激光束穿过钨丝圈而不触及钨丝,发现在热分解温度阈值以下,一旦用红外激光辐照,分解反应立即发生,如停止辐照,反应也就停止。在 SF_6体系的实验中,研究了 SF_6在多晶纯铂丝表面上的热分解反应动力学。当 SF_6的压力在0.050—0.15托之间,测得分解反应的起始温度为900℃左右。当铂丝温度在900—1050℃范围内,反应速率与 SF_6的压力呈一级反应关系,测得反应表现活化能为19.6千卡/摩尔。在     

红外多光子分解SF_6分离硫同位素的实验研究

本文报导了用能量1—1.5J,脉冲半宽度100—200nsTEA CO_2激光照射SF_6,实现红外多光子分解,分离硫同位素。全文共有七项结果:(1)0.20托SF_6,加入不同比例的H_2,照射相同数目(800个)激光脉冲,观察分离系数α值的变化。当H_2的分压为0时,α值为17;而当H_2的分压增加到1.80时,α下降到3。(2)自由基和分解后产物的复合反应对分离有较大的影响,由反应器材质(黄铜、玻璃)不同,得到间接验证。(3)分离系数α与照射的激光脉冲次数S间的关系。在有限的脉冲数范围内,α随S的增加指数地增加,增加率是SF_6压力的函数。(4)分离系数α与SF_6压力P间的关系。纯SF_6情况下,α随压力增加而迅速减小,减小率是脉冲数的函数;在SF_6/H_2=1/5的情况下,α值随压力增加而指数地下降。(5)平均分解产额与SF_6压力间的关系,存在一极大值。在本实验条件下,压力为1.60托左右时,分解产额最大。(6)不同缓冲气体对分离的影响与缓冲气体对SF_6分子振动能量弛豫时间的影响趋势相一致。(7)激光照射SF_6分子时分析可能的分解反应渠道。对激光照射后进行剩余气体成份的分析,发现有大量     

热激励的HF化学激光器

为了热分解 NF_3和 SF_6成氟原子并与 H_2反应产生 HF 激光运转,应用了 CIN_3爆炸激励。由4→3HF 激光跃迁表明氢原子与含氟物的反应。     

CF_2Cl_2十SF_6的激光裂解

本文采用CW CO_2激光器研究了SF_6+F_(12)在不同条件下的激光诱导化学反应,并与热反应进行了对照。证明SF_6在F_(12)的激光裂解中是一光敏剂,能使F_(12)的分解分数大大提高。整个反应为碰撞级联激发过程,而非多光子过程。     

激光分离铀同位素几个基本问题的初步研究与分析

本文对激光分离铀同位素分子体系(UF_6)的分离系数与产额,温度对UF_6红外吸收光谱结构的影响,建立流动低温装置的必要性与可能性,进行了研究与分析。文中以红外多光子诱导化学反应和红外双频多光子分解方法为对象,建立了分离系数与产额近似的理论公式,并作了详细的分析与讨论,指出:要获得高分离系数与高分离产额应当选择反应过程是非放热的;起始温度低于分子热激发至反应能级所需要的温度;反应特征时间τ_(re)应大于分子在激发态的寿命τ_(mn)和分子问的碰撞时间τ_(col),即τ_(re)■τ_(mn)■τ_(col);激发线宽要窄和同位素吸收光谱要分散开。在理想的情况下,分离系数等于两同位素吸收截面比。本文还研究了温度对UF_6分子振转光谱结构的影响。对不同温度下,UF_6分子振转光谱中P-R 支强峰间距离△ν_(P-R),进行了计算。指出当UF_6气体温度降到100°K 时,△ν_(P-R)值约为室     

基于激光光声光谱超高灵敏度检测SF_6分解组分H_2S

H_2S是SF_6气体绝缘设备中放电故障诊断的特征组分之一;针对H_2S在红外波段吸收系数小,传统光学检测方法对H_2S检测灵敏度较低的问题,结合大功率光纤激光放大技术、共振式激光光声光谱技术、波长调制光谱技术和二次谐波检测技术,提出了一种基于光纤放大激光光声光谱的SF_6分解组分H_2S气体的超高灵敏度检测方法;采用近红外可调谐窄线宽分布反馈激光二极管级联高饱和输出功率掺饵光纤放大器作为光声激发光源,搭建具有超高灵敏度的激光光声光谱微量H_2S气体检测系统。结果表明:当测量时间为100s时,该系统对SF_6背景中H_2S气体的检测极限达到1.5×10~(-8)。     

SF_6无多普勒饱和吸收光谱技术

建立了一套用直流放电激励的 CO_2激光研究 SF_6低压气体无多普勒饱和吸收光谱的实验装置。为使实验分辨率趋近10~(-8),对影响实验分辨率的各种因素,请如各种谱线展宽、激光频率和功率的稳定性等做了量级上的估算,并提出了相应的限制和要求。给出了满足这些要求所应采取的具体技术措施。其中主要有:用补偿式热稳定支架来稳定激光腔长,用辅助金镜增强反射光强的办法来示踪弱红外光以及使用防震台和环境空训等。此外,也讨论了如何用压电陶瓷测量频率间隔等一些具体实验细节。利用本装置观察到了 CO_2激光 P(18)线内的 SF_6饱和共振峰。并在气体压强分别为40和     

部分离解的SF_6分子中的非线性弛豫

用一台可调谐的TEA CO_2激光器强激励纯SF_2以及SF_6与缓冲气的混合气体,测量了振动-平动(VT)弛豫时间对激励激光频率的依赖关系。在一些激励频率下,观测到VT弛像时间发生显著的减小。若与SF_6分子的线性红外吸收谱相比,这些频率发生强烈的红移和谱展宽。特别是,在特定的实验条件下,整个弛像过程可用两个不同的速率来表征,这与强受激分子发生了部分离解有关。     

Simultaneous emission of the HF and N2 lines from aplasma cathode TEA laser

Simultaneous laser action from HF and N₂ is obtained, from a plasma cathode TEA laser, for the first time. The sliding discharge along the surface of a dielectric is used as a plasma cathode, for the main volumetric discharge. The laser operates at atmospheric pressure, with a gas mixture of SF₆:C₃H₈:N₂:He. For a typical flow rate ratio of 0.27:0.024:0.2:19.8 1 min^-1, it produces simultaneously 160 mJ HF and 0.6 mJ N₂ laser outputs at 0.43% and 1.4×10^-3% efficiencies respectively, at the moderate charging voltage of 28.5 kV. These output characteristics are obtained from a small active discharge volume and length of 10⁶ cm³ and 38 cm respectively. These values extend the performance, recently reported in the literature, of a sliding discharge HF/N₂ laser with corresponding simultaneous energy outputs of 12 mJ HF and 1.1 mJ N₂, to a higher energy output level, thus making the device suitable for a broader range of applications. This novel dual wavelength HF/N₂ laser system presented, can be particularly convenient for medical experiments, where the IR beam can be used for tissue ablation, while the UV beam can be used as the excitation source for fluorescence spectroscopic measurements, for the evaluation of the ablation process. Details are presented on the dependence of the laser performance parameters, such as output energy, discharge voltage and current and structure of the laser output pulses on the mixture composition and the circuit parameters     

Impurity local phonon nonradiative quenching of Yb3+fluorescence in ytterbium-doped silicate glasses

We have studied the concentration quenching of Yb³⁺ ion fluorescence in Yb-doped silicate glasses containing up to 3.4×10 ²¹ cm^-3 Yb³⁺ ions. The absorption and fluorescence spectra are similar to those obtained for the Yb³⁺ ion in many different matrices, with a radiative lifetime of approximately 1400 μs. The fluorescence decay curves were different among samples, with strong dependence on the Yb concentration. The decay curves could always be resolved into two exponential components, indicating that the ions reside in two different sites, each of a different characteristic nonradiative decay mechanism. The fast decay times ranged between 6 and 300 μs, and the slow ones ranged between 190 and 1250 μs in different samples. The sites where ions exhibit the fast decay most probably consist of pairs of Yb³⁺ ions. The nonradiative decay probabilities for each site mere directly proportional to the Yb³⁺ concentration in the same site. We propose that the fluorescence quenching occurs by multiphonon nonradiative transitions involving polar local phonon bands created by the presence of the Yb³⁺ ion     

Ba原子6s2 1S0 - 6s6p3P1跃迁Hanle效应实验研究

Ba原子是光频标的候选者之一,对其进行有效的激光冷却与囚禁需要相关能级的寿命和跃迁几率的信息。Ba原子激发态6s6p 3P1能级在激光冷却实验中很重要,通过Hanle效应实验测量了这一能级的寿命和自发辐射率,从理论和实验上研究了探测激光有限线宽和光强对Ba原子基态6s2 1S0与激发态6s6p 3P1之间跃迁（波长791 nm）的Hanle效应的荧光信号的影响。在考虑了激光线宽和光强因素后所得到的激发态6s6p 3P1的能级寿命和自发辐射率与其他方法给出的结果很好符合。     

Time—resolved Photoluminescence Spectra of Nominally Disordered GaInP Alloy

Luminescence decay and time-resolved photoluminescence(TRPL) spectra are used for study on the transient luminescence process of the nominally disordered GaInP alloy.The luminescence decay of GaInP alloy shows the temperature and excitation-intensity dependent characters.At 77K and under high excitation intensity, the luminescence decay shows single exponential time dependence, while under low excitation intensity or at 300 K, the luminescence decay shows double exponential time dependence.The analysis indicated that this nominally disordered GaInP alloy actually exhibits a very weak degree of order.The blue-shift of PL peak is observed in the TRPL spectra at 77 K, which is derived from the transfer of the carriers from the ordered domain to the disordered region of the alloy.At 300 K, due to the thermal quenching, the transfer is too weak to be observed.However,The recombination of the carriers between the ordered domain and the disordered region is still devoted to luminesce.     

The effect of the geometry of the active medium on the performanceof SF6+H2 pumped HF laser

Experimental study of a pulsed, electric-discharge-initiated, SF ₆+H₂ pumped HF chemical laser is presented. The reactants were premixed and the laser medium was preionized by means of a plasma cathode. The laser pulse energy, as a function of the discharge voltage, was measured for various laser medium parameters. It was concluded that the ratio between the width and height of the active volume is an important issue in the laser performance     

Superfluorescence dynamics in 130Te2

High-resolution analysis results are presented for Te₂ superfluorescence induced by short pulses from a YAG-pumped dye laser pulses, and a comparison is made with CW-laser-induced fluorescence observed by Fourier transform spectroscopy. A complete identification of the transitions involved, based on intensity measurements and supported by calculated Franck-Condon factors, has been achieved. The cooperative emission in Te₂ has been studied by time resolved spectroscopy as a function of density. With increasing density or temperature of the sample, the emission changes continuously from characteristic spontaneous emission to superfluorescence. The evolution of the time characteristics of the signal with the number of partners are presented and compared with the predictions of current theories     

NdP_5O_(14)晶体中Nd~(3+)的4F_(3/2)受激态上粒子数对荧光寿命的影响

研究了室温下 NdP_5O_(14)晶体中 Nd~(3+)的4F_(3/2)态的荧光寿命。观察到高泵浦强度下影响光学增益的荧光双指数衰减曲线。从能量传递过程进行理论分析。简单描述了脉冲若丹明6G 激光器选择泵浦的τ计。     

小功率连续波放电DF/HF化学激光器的功率

将SF6、O2、He3种可调气体预混合,喷入带有8个高压放电极的放电管,解离F离子,沿气流方向以亚音速喷入喉道,H2/D2由喉道上下喷入,光轴在H2/D2喷入下游1mm处。研究了连续波DF/HF激光器的多谱线输出功率与SF6、He和H2/D2的流量关系,以及混合气体中加入O2对激光器性能的影响。实现了HF最大输出功率12W,DF最大输出功率11W,连续可调,功率稳定,持续时间20min。     

超音速F-F_2-NH_3体系中产生的 NF(b~1∑~ )——一种可能的可见化学激光介质

采用经过改装的连续波超音速HF化学激光器,在F-F_2-NH_3体系中成功地直接产生电子激发态NF(b~1∑~ ),测得了NF(b~1∑~ )化学发光强度沿气流方向的分布,并由此求得了NH_3和DF分子对NF(b~1∑~ )的猝灭速率常数。     

Pressure dependency of the NF3-H2transverse-discharge pulse-initiated HF chemical laser

The pressure dependency of the performance of the NF3-H2chemical-laser system has been evaluated. The laser energies at various chemical compositions and initiation discharge energies are presented as functions of Pressure. Overall efficiency, laser pulsewidth, and effects of additive gases are also presented. For all compositions the laser energy maximized at a pressureP_{max}which was observed to be dependent on the pulsewidth of the initiation discharge. At pressures belowP_{max}the laser energy was proportional to the partial pressure of NF3or H2. No change in slope of the laser energy versus pressure curve was observed in going from low-pressure nonexploding regimes to high-pressure exploding regimes, implying that the reactions causing the explosion did not contribute to the lasing. Lasing usually occurred in two peaks, the first containingHF(V=2) rightarrow HF(V=1)lines and the second containingHF(V=3) rightarrow HF(V=2)andHF(V=1) rightarrow HF(V=0)lines. These data indicate that lasing is due to the reaction sequence: 1)NF_{3} + e^{-} = cdot NF_{2} + Fcdot + e^{-}; 2) Fcdot + H_{2} = HF+(V) + Hcdot; and 3)HF+(V) + hnu = HF+(V-1) + 2hnu.