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Near-threshold structure of molecular hydrogen at the 1s + 2l dissociation limit 分子氢在1s + 2l解离极限下的近阈值结构
Pub Date : 1900-01-01 DOI: 10.1364/hrs.1993.tha3
E. Eyler, B. F. Catching, N. Melikechi
High-resolution measurements of molecular structure very near a dissociation limit can be used both to probe long-range atomic interactions and to make accurate determinations of dissociation energies. Our research group has investigated the H(1s) + H(2s or 2p) dissociation limit in molecular hydrogen using optical double resonance with single-mode lasers. Fig. 1 shows the general scheme of the experiment. Our measurements of bound states in H2, reported in Ref. 1, have now been extended to include the adjoining continuum and the other stable isotopomers, HD and D2. The most weakly bound levels to which transitions are seen are bound by only about 0.03 cm−1, equivalent to about 40 mK. Very sharp continuum resonances are also observed in the region just above threshold.
非常接近解离极限的分子结构的高分辨率测量既可以用来探测远距离原子相互作用,也可以用来精确测定解离能。本课课组利用单模激光光学双共振研究了氢分子中H(1s) + H(2s或2p)的解离极限。实验总体方案如图1所示。我们对H2束缚态的测量,在Ref. 1中报道,现在已经扩展到包括相邻连续体和其他稳定同位素,HD和D2。能观察到跃迁的最弱束缚能级仅受约0.03 cm−1束缚,相当于约40 mK。在略高于阈值的区域也观察到非常尖锐的连续共振。
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引用次数: 2
The Position, Shape, and Polarization Dependence of Resonances in the Laser Photoionization Spectrum of Aligned Ca 4s5p 1P1
Pub Date : 1900-01-01 DOI: 10.1364/hrs.1993.wb3
D. Duquette, K. Mclaughlin, D.S. Eschliman, O. Francis
Two-color spectroscopy using narrow-bandwidth pulsed lasers provides a powerful tool to study the near threshold photoionization spectrum of excited atomic states. By combining the energy and polarization selectivity afforded by pulsed dye lasers, it is possible to probe a number of different continua. Many of these would be unreachable from the ground state because of angular momentum and parity selection rules and also due to the lack of high resolution sources of photons at appropriate energies. Precise positions, shape profiles, and strengths of autoionizing resonances, as well as angular distributions of ejected photoelectrons are necessary for comparison with increasingly sophisticated calculations.
窄带脉冲激光双色光谱为研究原子激发态的近阈值光离光谱提供了有力的工具。通过结合脉冲染料激光器提供的能量和偏振选择性,可以探测许多不同的连续体。由于角动量和宇称选择规则,并且由于缺乏适当能量的高分辨率光子源,许多这些从基态是无法到达的。精确的位置,形状轮廓,和自电离共振的强度,以及射出光电子的角度分布是必要的,以比较日益复杂的计算。
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引用次数: 0
High Resolution Electronic Spectroscopy of Hydroxyl-Rare Gas Complexes 羟基-稀有气体配合物的高分辨率电子光谱
Pub Date : 1900-01-01 DOI: 10.1364/hrs.1993.tua3
Bor-Chen Chang, J. Williamson, J. R. Dunlop, T. Miller
For many years, scientists have studied the spectroscopy of van der Waals complexes in past to understand intermolecular interactions and potential energy surfaces. There are abundant experiments and theoretical calculations on the closed-shell van der Waals complexes.1,2 Relatively speaking, the open-shell complexes have attracted much less attention until recently. The sparsity of information is due to both the difficulty of preparing the species and the complexity of their spectroscopy, which involves both unquenched electronic orbital and spin angular momenta. In the past four years, there have been several experimental and theoretical papers centered on Ar•OH/D and Ne•OH/D.3,4 However, except for one microwave experiment5 the previous works lack information about fine and hyperfine structure due to the resolution limit of dye laser used in the laser-induced fluorescence (LIF) studies.
多年来,科学家们一直在研究范德华配合物的光谱,以了解分子间的相互作用和势能表面。关于闭壳范德华配合物有大量的实验和理论计算。相对而言,开壳配合物直到最近才引起人们的注意。信息的稀疏性是由于制备的困难和光谱的复杂性,这涉及到未淬灭的电子轨道和自旋角动量。在过去的四年里,有几篇以Ar•OH/D和Ne•OH/D为中心的实验和理论论文。3,4然而,由于激光诱导荧光(LIF)研究中使用的染料激光器的分辨率限制,除了一个微波实验外,以往的工作缺乏关于精细和超精细结构的信息。
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引用次数: 0
Infrared-Molecular Beam Spectroscopy: the Study of Weakly Bound Molecular Complexes as a Probe of Potential Energy Surfaces and Molecular Dynamics 红外分子束光谱:弱结合分子配合物作为势能表面和分子动力学探针的研究
Pub Date : 1900-01-01 DOI: 10.1364/hrs.1993.tua2
Roger E. Miller
Infrared laser spectroscopy has become a powerful tool in the study of weakly bound molecular complexes. The molecular constants obtained from these spectra can be used to determine the "structure" of the complex, for systems where this is a meaningful concept, while, in complexes which undergo wide amplitude excursions from their equilibrium geometries, the spectroscopy is often sensitive to the details of the intermolecular potential energy surface. In many cases, these spectra are sensitive to both the internal dynamics of the complex and the vibrational predissociation dynamics that result from the excitation process.
红外激光光谱已成为研究弱结合分子络合物的有力工具。从这些光谱中获得的分子常数可用于确定配合物的“结构”,对于这是一个有意义的概念的系统,而在从其平衡几何形状经历宽振幅漂移的配合物中,光谱通常对分子间势能表面的细节很敏感。在许多情况下,这些光谱对配合物的内部动力学和激发过程产生的振动预解离动力学都很敏感。
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引用次数: 0
High Resolution Spectroscopy of Ti2 and AlY at Near-Infrared Frequencies Ti2和AlY近红外高分辨光谱研究
Pub Date : 1900-01-01 DOI: 10.1364/hrs.1993.pd4
C. A. Arrington, Jon D. Langenberg, J. C. Pinegar, M. Morse, M. Doverstål, B. Lindgren, U. Sassenberg
High resolution jet-cooled molecular beam spectroscopy has been effective in revealing the bonding between transition metals. One periodic trend that has developed during the study of small transition metal molecules is the relatively weak bond strength in the early 3d transition metals (Sc2, Ti2 in comparison to middle (V2, Cr2) or late (Ni2, Cu2) members of the 3d series. This trend of bond strengths in early transition metals is not so pronounced in the 4d and 5d metals where d-bonding is a major contributor to molecular stability. Low bond strengths in molecules, whether due to poor d overlap or high s ← d promotion energy, provides a challenge to the spectroscopist. It has been shown that diatomic systems with a large density of electronic states, as is usually the case for open d-subshell molecules, undergo a rapid predissociation (τ < 5 ns) when excited above the lowest dissociation limit.1 The extreme density of states responsible for predissociation also precludes isolation of single rovibronic states suitable for high resolution spectroscopy at energies near the dissociation limit of these molecules. The spectroscopist interested in investigating species with low bond strengths and high densities of electronic states, as in our investigation of Ti2 and AlY, is forced to search the low energy near-infrared region for isolated electronic states that are not hopelessly perturbed. In the present near-infrared investigation of Ti2 and AlY we have employed resonant two photon ionization (R2PI) as the detection strategy for obtaining optical spectra in a jet-cooled molecular beam.
高分辨率射流冷却分子束光谱在揭示过渡金属之间的键合方面是有效的。在小过渡金属分子的研究中,一个周期性的趋势是,与3d系列的中间(V2, Cr2)或后期(Ni2, Cu2)成员相比,早期3d过渡金属(Sc2, Ti2)的键强度相对较弱。在4d和5d金属中,早期过渡金属的键强度趋势不那么明显,其中d键是分子稳定性的主要贡献者。分子中的低键强度,无论是由于差的d重叠还是高的s←d促进能,都给光谱学家带来了挑战。研究表明,具有大电子态密度的双原子体系,如通常的开放d亚壳分子,当激发到最低解离极限以上时,会经历快速的预解离(τ < 5 ns)负责预解离的状态的极端密度也排除了在接近这些分子解离极限的能量处适合于高分辨率光谱的单振动态的分离。对研究具有低键强度和高密度电子态的物质感兴趣的光谱学家,就像我们对Ti2和AlY的研究一样,被迫在低能量的近红外区域寻找孤立的电子态,这些电子态不是毫无希望地被扰动的。在目前对Ti2和AlY的近红外研究中,我们采用共振双光子电离(R2PI)作为探测策略来获得喷气冷却分子束的光谱。
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引用次数: 0
High Resolution Spectroscopy on Single Molecules 单分子的高分辨率光谱学
Pub Date : 1900-01-01 DOI: 10.1364/hrs.1993.wa5
J. Sepioł, F. Güttler, M. Pirotta, A. Renn, U. Wild
Single particle spectroscopy has become a source of valuable information on fundamental interactions between light and matter. Whereas trapping and cooling of ions and atoms has been sucessfully achieved, single molecules, because of their multilevel structure (high number of internal degrees of freedom) have not been observed in electromagnetic traps so far. However due to the presence of zero phonon lines in conjunction with inhomogeneous broadening the spectroscopic isolation and detection of single molecules ‘trapped in solids at very low temperatures' is made feasible [1,2]. Single molecule spectroscopy allows to study the distribution of molecular properties and not only the statistical average which is generally observed.
单粒子光谱学已成为研究光与物质之间基本相互作用的宝贵信息来源。虽然离子和原子的捕获和冷却已经成功实现,但单分子由于其多层结构(高内部自由度)到目前为止还没有在电磁陷阱中观察到。然而,由于零声子线的存在以及非均匀展宽,使得“在极低温度下被困在固体中的”单分子的光谱分离和检测成为可能[1,2]。单分子光谱学可以研究分子性质的分布,而不仅仅是通常观察到的统计平均值。
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引用次数: 0
Molecular collisions at very low temperature 分子在低温下的碰撞
Pub Date : 1900-01-01 DOI: 10.1364/hrs.1993.tua5
F. D. De Lucia
We have reported a number of investigations in which a newly developed collisional cooling method was used to investigate collisional processes between gas phase atoms and molecules at very low temperatures.1-7 In these studies the molecules are effectively in thermodynamic equilibrium with their collision partners, but at temperatures far below their freezing points. Used in conjunction with conventional equilibrium cells, measurements over the entire 1 - 1000 K region can be made. This range makes possible both the observation of new collision phenomena at low temperature and the study of collisions over a wide enough range to consider the collisions spectroscopically.
我们已经报道了一些研究,其中一种新开发的碰撞冷却方法用于研究气相原子和分子在极低温度下的碰撞过程。在这些研究中,分子与它们的碰撞伙伴实际上处于热力学平衡状态,但温度远低于它们的冰点。与传统的平衡细胞结合使用,可以测量整个1 - 1000 K区域。这个范围使得在低温下观察新的碰撞现象和在足够宽的范围内研究碰撞以从光谱上考虑碰撞成为可能。
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引用次数: 0
b-Dipole Transitions in X ˜ 2A' t-HOCO Observed by FIR Laser Magnetic Resonance 用FIR激光磁共振观察X ~ 2A′t-HOCO中的b-偶极子跃迁
Pub Date : 1900-01-01 DOI: 10.1364/hrs.1993.thb1
T. Sears, H. Radford, M. Moore
The HOCO radical is crucially important in combustion chemistry as the intermediate in the reaction between hydroxyl radicals and carbon monoxide. Studies of the temperature dependence of the rate constant for this reaction implied the existence of the radical intermediate1 but only very recently was HOCO detected in the gas phase2,3. Both the infrared spectrum3, which is due to the perturbed C=O stretching fundamental (v2), and the observed rotational spectrum2 consist only of a-dipole transitions. Such transitions obey the selection rule ΔKa = 0 in this near prolate top rotor and as such contain no direct information on the spacings between energy levels of different Ka. The high precision of the millimeter wave data allowed an approximate value for the A rotational constant to be derived2 however the accuracy with which it is known is much less than for B and C. Nonetheless, when combined with data for DOCO, it was possible to unequivocally attribute the spectra as due to the trans- geometrical isomer of the radical2.
HOCO自由基作为羟基自由基与一氧化碳反应的中间体,在燃烧化学中起着至关重要的作用。对该反应速率常数的温度依赖性的研究暗示了自由基中间体的存在,但直到最近才在气相中检测到HOCO。红外光谱3(这是由于C=O拉伸基元(v2)的扰动)和观测到的旋转光谱2都只由a偶极子跃迁组成。这种跃迁在近长顶转子中服从选择规则ΔKa = 0,因此不包含不同Ka能级之间间距的直接信息。高精度的毫米波数据允许推导出A旋转常数的近似值2,但已知的精度远低于B和c。尽管如此,当与DOCO数据结合时,可以明确地将光谱归因于自由基的跨几何异构体2。
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引用次数: 0
Molecular Spectroscopy at Ultracold Temperatures 超低温下的分子光谱学
Pub Date : 1900-01-01 DOI: 10.1364/hrs.1993.pd12
K. Helmerson, M. Wagshul, P. Lett, S. Rolston, W. Phillips
Associative ionization (AI) in sodium (Na + Na + 2 hv → Na2+ + e−) has been a convenient reaction in which to study excited state collisions under "ultracold" conditions (≤1 mK) because the reaction product is easily identified and collected with high signal-to-noise. Previous studies [1] have revealed evidence of molecular intermediate-state resonances under high-intensity laser conditions. Theoretical analysis [2] has associated this structure with singly- and doubly-excited Na2 intermediate states. In this work, we present a new technique utilizing a switched magneto-optical trap (MOT) to make clean measurements of the spectrum of associative ionization in a regime where we can identify the peaks as being associated with states of the Na2 molecule. In addition, our technique reveals new structure in the spectrum of AI versus laser frequency, pointing out the previously unappreciated importance of atomic hyperfine structure in the reaction.
钠(Na + Na + 2hv→Na2+ + e−)的缔合电离反应(AI)由于其反应产物易于识别和采集,具有高信噪比,是研究“超冷”(≤1mk)条件下激发态碰撞的方便反应。先前的研究已经揭示了在高强度激光条件下分子中间态共振的证据。理论分析[2]将这种结构与单激发和双激发的Na2中间态联系起来。在这项工作中,我们提出了一种利用开关磁光阱(MOT)的新技术,在一个可以识别与Na2分子状态相关的峰的状态下,对缔合电离光谱进行干净的测量。此外,我们的技术揭示了AI光谱与激光频率的新结构,指出了原子超精细结构在反应中的重要性。
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引用次数: 0
Bond Energies of Small Transition Metal Cation Clusters 小过渡金属阳离子团簇的键能
Pub Date : 1900-01-01 DOI: 10.1364/hrs.1993.pd2
L. Russon, Scott A. Heidecke, M. Birke, J. Conceição, P. Armentrout, M. Morse
A new experimental apparatus has been constructed for photodissociation spectroscopy of transition metal-containing cations. redissociation thresholds for Co 2 + , Co 3 + , and Ti 2 + have been observed and values of 2.765 ± 0.001 eV, 2.086 ± 0.002 eV, and 2.435 ± 0.002 eV, respectively, have been determined for the bond energies for these species. These are in good agreement with results obtained by collision-induced dissociation (CID) experiments. Comparison of bond strengths obtained from the observation of predissociation thresholds with those obtained by non-optical methods, such as collision-induced dissociation and Knudsen cell mass spectrometry, have allowed criteria for the interpretation of a pre-dissociation threshold as a bond strength to be developed.
建立了一种新的含过渡金属阳离子光解光谱实验装置。Co 2 +、Co 3 +和Ti 2 +的键能分别为2.765±0.001 eV、2.086±0.002 eV和2.435±0.002 eV。这与碰撞诱导解离(CID)实验的结果一致。将预解离阈值与非光学方法(如碰撞诱导解离和Knudsen细胞质谱)获得的键强度进行比较,可以建立将预解离阈值解释为键强度的标准。
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引用次数: 0
期刊
High Resolution Spectroscopy
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