Frequency measurements in the 9μm spectrum of CF3Br

Carbon dioxide laser saturation spectra of CF₃ Br have been explored with a view to hyperfine spectroscopy and references for frequency standards in the 9μm band of the carbon dioxide laser. Spectra have been obtained using the laser transitions 9R(16)-9R(30). and show many saturation features in each case. Several of the stronger features have been referenced directly to CO₂ frequencies with an estimated accuracy of 25 kHz. Spacings between the hyperfine components are also reported. This work represents some of the first data relevant to 9μm locking to molecular absorptions.     

A high level computational study of the CH4/CF4 dimer: how does it compare with the CH4/CH4 and CF4/CF4 dimers?

The interaction within the methane–methane (CH₄/CH₄), perfluoromethane–perfluoromethane (CF₄/CF₄) methane–perfluoromethane dimers (CH₄/CF₄) was calculated using the Hartree–Fock (HF) method, multiple orders of Møller–Plesset perturbation theory [MP2, MP3, MP4(DQ), MP4(SDQ), MP4(SDTQ)], and coupled cluster theory [CCSD, CCSD(T)], as well as the PW91, B97D, and M06-2X density functional theory (DFT) functionals. The basis sets of Dunning and coworkers (aug-cc-pVxZ, x?=?D, T, Q), Krishnan and coworkers [6-311++G(d,p), 6-311++G(2d,2p)], and Tsuzuki and coworkers [aug(df, pd)-6-311G(d,p)] were used. Basis set superposition error (BSSE) was corrected via the counterpoise method in all cases. Interaction energies obtained with the MP2 method do not fit with the experimental finding that the methane–perfluoromethane system phase separates at 94.5?K. It was not until the CCSD(T) method was considered that the interaction energy of the methane–perfluoromethane dimer (?0.69?kcal?mol^?1) was found to be intermediate between the methane (?0.51?kcal?mol^?1) and perfluoromethane (?0.78?kcal?mol^?1) dimers. This suggests that a perfluoromethane molecule interacts preferentially with another perfluoromethane (by about 0.09?kcal?mol^?1) than with a methane molecule. At temperatures much lower than the CH₄/CF₄ critical solution temperature of 94.5?K, this energy difference becomes significant and leads perfluoromethane molecules to associate with themselves, forming a phase separation. The DFT functionals yielded erratic results for the three dimers. Further development of DFT is needed in order to model dispersion interactions in hydrocarbon/perfluorocarbon systems.     

On the absolute efficiency of large neutron detectors for μCF

The absolute efficiency for a large organic scintillator neutron detector has been calculated via Monte Carlo simulation for neutrons of 14 MeV. The influence of the environmental geometry (source scattering, etc.) has been taken into account. Full differential cross-sections, including resonances, have been used. The calculated response function compares well with the measured one. This revised version was published online in August 2006 with corrections to the Cover Date.     

Diode laser spectroscopy of the ν1-ν3 band of CF335Cl at 15.84 μm

The vibration-rotation spectrum of CF₃Cl, with natural isotopic abundance, has been recorded in the 622- to 641-cm⁻¹ region using a tunable diode laser spectrometer. The K structure of many P(J) and R(J) manifolds of the ν₁-ν₃ difference band of CF₃³⁵Cl has been resolved and positively identified. The rotational analysis has been extended in the P and R branches up to J = 39 and 47, respectively, and more than 650 lines have been assigned. A least-squares fit of the observed transitions to the energy expression including the quartic centrifugal distortion terms was performed and molecular constants for the ν₁-ν₃ difference band were determined. From the obtained parameters the ν₃ band center of CF₃³⁵Cl was evaluated as 476.9750(4) cm⁻¹ and the values of α₃^A and α₃^B were derived to be 50(1) × 10⁻⁶ and 82.9(6) × 10⁻⁶ cm⁻¹, respectively.     

CF3Cl，CF2Cl2 和CFCl3分子外价壳层轨道特性的电子动量谱学研究

通过比较相同电子成分轨道的实验和DFT-B3LYP/6-311+G*理论的电子动量分布,系统研究了CF3Cl,CF2Cl2 和CFCl3分子外价壳层的轨道特性.研究结果表明CF3Cl,CF2Cl2 和CFCl3分子的Cl（3p）孤对电子轨道随着Cl原子个数增多,分子内相互作用逐渐增强,Cl原子3p轨道电子动量分布的特征逐渐淹没;F孤对电子轨道和的电子动量分布在高动量区出现了一个弱结构,且随Cl原子个数增多和F原子个数减少逐渐消失,这可能是由于部分轨道C-Cl 键电子成分的贡献;除3a1轨道外,C-F成键轨道和的理论的电子动量分布均在低动量端低于实验结果,可能是由于“d-like” 轨道低动量端的扭曲波效应;3a1轨道理论的电子动量分布均在 范围内低于实验结果,可能是由于扭曲波效应和电子关联等效应的影响.     

Electron Momentum Distributions of the Highest Occupied Molecular Orbital of CF3Br： Delocalization of Halogen Lone-Pair Orbitals

The highest occupied molecular orbital (HOMO) of trifluorobromomethane (CF3Br) is studied by binary (e,2e)electron momentum spectroscopy. The experimental momentum profile of the HOMO is compared with the Hartree-Fock (HF) and density functional theory (DFT-B3LYP) calculations. The calculated results largely depend on the size of basis sets rather than theoretical methods. Both the HF and DFT calculations using the 6-311 G^** basis set give a good explanation to the experiment. Delocalization of halogen lone-pair orbitals in the series molecules CF3X (X=F, Cl, Br) has been investigated.     

New approach to the old problem of muon sticking in µCF

A new approach is presented for evaluation of the muon sticking probability to helium in muon-catalyzed fusion reactions. Use of the sudden approximation is avoided. The probability _s of muon sticking to helium in the reaction dtµ µ⁴He+n, calculated with the new method, agrees with previous results. Moreover, the energy and angular distributions for the emitted muon, as well as the dependence of w_s on the energy radiated during the muon-catalyzed fusion event, have been evaluated.     

Double resonance spectroscopy of freon 12: Hot bands of CF235Cl2 and CF235Cl37Cl and the ν6 fundamental of CF237Cl2

Computer-assisted analysis of hundreds of double resonance signals from CF₂Cl₂ has yielded constants for the hot bands ν₆ + ν₄ − ν₄ of CF₂³⁵Cl₂ and CF₂³⁵Cl³⁷Cl and ν₆ + ν₅ − ν₅ of CF₂³⁵Cl₂. It has also produced the first experimental data over the ν₆ fundamental of CF₂³⁷Cl₂.     

A photoelectron spectroscopic study of the second ionisation of the CF(X2Π) radical

The CF(X²Π) radical has been re-investigated with vacuum ultraviolet photoelectron spectroscopy. Two bands were observed and assigned to the ionisations CF⁺(X¹Σ⁺)←CF(X²Π) and CF⁺(a³Π)← CF(X²Π). The first band, which has been observed previously, has an adiabatic ionisation energy of (9.11±0.02) eV and a vertical ionisation energy of (9.55±0.02) eV. For the second band, three vibrational components were observed with the first, the most intense, at an ionisation energy of (13.94±0.02) eV. Analysis of the vibrational structure in the two observed bands allowed ω_e and r_e to be determined as 1810±30 cm⁻¹ and 1.154±0.005 Å, respectively for the first ionic state, CF⁺(X¹Σ⁺), and 1614±30 cm⁻¹ and 1.213±0.005 Å, respectively for the second ionic state, CF⁺(a³Π). Comparison of the ionisation energies and spectroscopic constants obtained has been made with values obtained from recent multi-reference configuration interaction calculations.     

飞秒时间分辨质谱方法研究CF3I光电离动力学

利用飞秒双色泵浦 探测 (pump probe)飞行时间质谱方法研究了CF3 I分子多光子电离动力学 ,所用泵浦光及探测光的中心波长分别为 2 6 5和 398nm .获得了母分子离子CF3 I+ 信号及其碎片离子CF3 + 和I+ 信号的寿命衰减常数分别为 (96± 7)、(198± 13)和 (16 7± 6 )fs.这些离子产生的多光子通道机理不同 :CF3 I来自 (1+2′)跃迁 ,单光子泵浦光与CF3 IA带共振 ;驭光子泵浦光激发CF3 I分子到 5 pπ7sδ(2 Π1/ 2 )里德伯态 ,单光子探测光电离产生的母分子离子解离产生CF3 + ;I+ 来自 (2 +2′)和 (1+1′ +2′)激发过程     

CH3CF2O2+HOO反应的理论研究

使用Gaussian98程序包，在B3LYP/6-311++G**基组水平上对CH3CF2O2+HOO的各反应通道进行了充分研究，过渡态和产物间的联系通过IRC确认．用振动模式分析和电子布居分析对所有反应通道进行了讨论以阐明反应机理．研究结果表明，在能量上CH3CF2CO2+HOO→IM1→TS1→CH3CF2O2H+O2通道最为有利，CH3CF2O2H和O2是主要产物，但CH3OH和CF2O的生成也是可能的．     

离子速度成像方法研究CF3I分子光解反应动力学

建立一套离子速度成像系统，这套系统通过采用最新的“速度映像”技术克服了离子源空间分布对速度分辨率造成的模糊。利用这套系统得到了ＣＦ３Ｉ在２７７ｎｍ附近光解反应产物Ｉ＾＊（＾２Ｐ１／２）和Ｉ（＾２Ｐ３／２）的速度和角度的高分辨率分布，首次利用重构的Ｉ（＾２Ｐ３／２）碎片三维空间速率分布揭示了其两个不同的解离通道。     

低温Ar基质中CF3I激光光氧化反应中间体研究

研究了１０Ｋ Ａｒ基质中ＣＦ３Ｉ与Ｏ２经２６６ｎｍ脉冲激光辐照的光氧化反应，利用低温基质隔离技术和付里叶变换红外光谱法检测反应过程中产生的中间体有ＣＦ３ＯＯＩ、ＣＦ３ＯＯ、ＣＦ３Ｏ和ＣＦ３ＯＩ。通过量子化学从头算，对ＣＦ３ＯＯＩ的结构和振动频率进行计算，并对观察到的３个吸收峰进行了归属，首次确证ＣＦ３ＯＯＩ为新的中间体，根据ＣＦ３ＯＯ、ＣＦ３ＯＯＩ、ＣＦ３Ｏ、ＣＦ３ＯＩ随光照时间的生长和衰减，提出     

A Modified Potential Method for Electrons Scattering Total Cross Section Calculations on Several Molecules at 30 ～ 5000 eV: CF4, CCl4, CFCl3, CF2Cl2, and CF3Cl

A complex optical model potential modified by the concept of bonded atom, which takes into consideration the overlapping effect of electron clouds between two atoms in a molecule, is employed to calculate the total cross sections (TCSs) for electrons scattering from several molecules (CF4, CCl4, CFCl3, CF2 Cl2, and CF3 Cl) over an incident energy range 30 ～ 5000 eV using the additivity rule model at Hartree-Fock level. The quantitative TCSs are compared with those obtained by experiments and other theories wherever available, and good agreement is obtained above 100 eV.It is shown that the modified potential can successfully calculate the TCSs of electron-molecule scattering over a wide energy range, especially at lower energies.     

The ro-vibrational analysis of the v4 fundamental band of CF3Br from jet-cooled diode laser and FTIR spectra in the 8.3-μm region

The v₄ fundamental band of CF₃⁷⁹Br and CF₃⁸¹Br, present in natural isotopic abundance, was investigated in the 8.3-μm region by high-resolution infrared spectroscopic techniques. Tuneable diode laser spectra were recorded in the ranges 1202.5–1205.0 cm^?1, 1208.0–1210.1 cm^?1 and 1212.5–1214.5 cm^?1. The tuneable diode laser spectra were obtained at the reduced temperature of 200 K and in a free-jet expansion. The latter technique was used to reduce spectral congestion, achieving a rotational temperature of about 50 K, with a resolution up to 0.0008 cm^?1. A Fourier transform infrared spectrum covering the entire spectral region of the v₄ band, between 1190 and 1220 cm^?1, was recorded at 298 K with a resolution of 0.004 cm^?1. The experimental wavenumbers from the different spectroscopic techniques were combined to accomplish the complete ro-vibrational analysis of v₄. In total, 4651 transitions were assigned to CF₃⁷⁹Br, 4047 to CF₃⁸¹Br, with J″_max? = K″_max?=80; of these, 3171 for CF₃⁷⁹Br and 2755 for CF₃⁸¹Br are from diode laser measurements. The data of each isotopologue were analysed using the model Hamiltonian for a degenerate vibrational state of a molecule of C_3v symmetry. The v₄ band of both the isotopologues resulted essentially unperturbed, but the Δl = Δk = ±2 l-resonance was found to be active within the v₄ = 1 state. Precise values of the vibrational energy and of the ro-vibrational parameters of v₄ = 1 for CF₃⁷⁹Br and CF₃⁸¹Br were obtained. The bromine isotopic splitting amounts to 6.9 × 10^?3 cm^?1. In addition, the equilibrium geometry and the harmonic force field were calculated ab initio using the large-size basis set def2-QZVP in conjunction to the PBE0 functional.     

New RIKEN-RAL pulsed µCF facility and X-ray studies on DT-µCF

In November 1994, the construction of a new superconducting muon channel of the RIKEN-RAL muon facility at ISIS of Rutherford Appleton Laboratory was completed. Subsequently, important features, such as the highest instantaneous intensity with a single-pulse structure and a high purity have been confirmed. Along with the installation of advanced µCF experimental equipment, including a high-purity D-T mixture target system with an in situ³He removal capability and a 4 T confinement magnet, an advanced µCF experiment, e.g. a precise X-ray measurement on µ- sticking in dtµ-µCF will be realized. An account of the commissioning experiments, a plan for the earliest phase of the µCF experiment and possible future directions are reported.     

Influence of epithermal muonic molecule formation on kinetics of the μCF processes in deuterium

The non-resonant formation of ddμ molecules in the loosely bound state in collisions of non-thermalized dμ atoms with deuterium molecules D₂ has been considered. The process of such a?type is possible only for collision energies exceeded the ionization potential of D₂. The calculated rates of ddμ formation in the above-threshold energy region are about one order of magnitude higher than obtained earlier. The role of epithermal non-resonant μ-molecule formation for the kinetics of μCF processes in D₂ gas was studied. It was shown that the non-resonant ddμ formation by dμ atoms accelerated during the cascade can be directly observed in the neutron time spectra at very short initial times.     

Implications of the recent D–T μCF experiments at RIKEN-RAL and near-future directions

The paper describes physics implications obtained through the recent experimental results on D–T μCF at RIKEN-RAL. Smaller sticking and larger cycling rates in solid/liquid D–T mixture than the theoretical predictions were observed, suggesting needs of further theoretical understandings. Some possible future directions in D–T μCF experiments are also described. This revised version was published online in August 2006 with corrections to the Cover Date.