Synchrotron X-ray study of sub-monolayers of CF4 on graphite

The quasi-two-dimensional solid and fluid phases of CF₄ physisorbed on the (001) surface of graphite were studied by means of X-ray diffraction at the electron storage ring DORIS, Hamburg. Four crystalline phases were observed, one of which is a registered 2 × 2 structure. On variation of temperature or coverage, the system experiences a phase transition from the 2 × 2 structure to a uniaxially compressed or “stripe” phase. This is unusual among gas-monolayer systems. Only at higher coverages does an isotropically compressed phase appear. At low temperatures we see a complicated structure giving three closely spaced diffraction peaks. We present diffraction data which characterize the melting of the stripe and the hexagonal incommensurate phases.     

ArF laser-induced discharge interruption in a mixture of C2H3Cl/CF4/CH4, CF4/CH4, and C2H3Cl/He

The ArF-laser (193-nm)-induced discharge interruption is comparatively described in a mixture of C₂H₃Cl/CF ₄/CH₄, CF₄/CH₄, and C₂ H₃Cl/He using a hollow-cathode-type discharge tube. The unfocused ArF laser (typically 27 mJ/cm² and 10 ns duration) illuminated both the negative glow inside the hollow cathode and the column between the two electrodes. With a 1.8-torr mixture of C₂ H₃Cl/CF₄, the discharge current of 1 mA was decreased rapidly with a current-decay time constant of 1 μs and a current-decay rate of 1 kA/s. With a 1.5-torr mixture of CF₄/CH₄, 2.2 μs and 450 A/s were obtained. With a 1.5-torr mixture of CH₂H₃Cl/He, a time constant of over 3 μs and a rate of less than 300 A/s were obtained. An analysis of the discharge interruption induced by ArF-laser irradiation is given in terms of photon-plasma kinetics. The current peak induced by ArF irradiation is also explained for a mixture of C₂H₃ Cl/He in terms of photoionization and photodetachment processes     

Photoionization of CF4 in the VUV region

We present calculated results of photoionization cross sections and photoelectron angular distributions for ionization out of the five outermost valence orbitals of CF₄ for photon energies ranging from near threshold to 55 eV. The Schwinger variational iterative method, using an exact static-exchange plus a model correlation–polarization potential, is applied to obtain the continuum photoelectron orbitals. The quantitative agreement between our calculated results and the experimental data is fair. Moreover, our study is capable of identifying most structures seen in experimental results for both cross sections and asymmetry parameters.     

Line shape of the collision-induced scattering in CF4

Results on the spectral shape of the collision-induced scattering (CIS) of CF₄ gas are obtained for densities up to 270 amagats (296 K). For low frequencies they are compared with dipole-induced dipole theory; for high frequencies a short distance-induced binary collision model describes the observed spectral shape fairly well.     

Experimental and theoretical investigations into the electronic structure of CF2Br2 by electron momentum spectroscopy

The binding energy spectra and electron momentum density distributions for the valence orbitals of CF₂Br₂ have been obtained by using electron momentum spectroscopy (EMS) at an impact energy of 1200 eV plus binding energy. The measured electron momentum profiles are compared with Hartree–Fock (HF) and density functional theory (DFT) calculations with different-sized basis sets. In general, the DFT-B3LYP calculation using the large basis sets of 6-311++G** and aug-cc-pVTZ fairly describe the experimental results. Moreover, the controversial orderings of the outer valence orbitals have been reassigned. The pole strength of the main ionization transition from the inner valence orbital of 1b₂ is determined.     

Collision-induced simultaneous transitions in H2+CF4 and H2+SF6 mixtures

The simultaneous transitions of the v₃ fundamental vibrations of CF₄ and SF₆ with the fundamental Q branch and S(1) line of H₂ have been studied for various H₂+CF₄ and H₂+SF₆ mixtures at total pressures up to 185 bars. The integrated intensities are found to be proportional to the partial densities of the gas mixture components. The agreement between experimental and calculated intensities is generally better for the Kihara potential than for the Lennard-Jones potential.     

双频容性耦合CF4等离子体放电的二维混合模拟

研究了等离子体反应装置内的等离子体密度、粒子能量与角度分布等参量在装置径向与轴向上的分布特性。在研究过程中应用二维混合模型对CF4气体放电进行模拟。计算结果显示:在电极表面与侧壁附近的鞘层区特性有明显的区别。由于装置侧壁处受电源产生的射频电场的影响较小,侧壁处的鞘层主要由双极扩散机制形成,其产生的径向电场强度较弱,鞘层厚度也较薄。而在电极附近,由于受到射频电场的影响,鞘层的厚度显著增加,指向电极方向的轴向电场强度也远大于指向侧壁方向的径向电场强度。在电极区域内,离子通量分布均匀;在电极边缘与侧壁的间隙内,因电场强度减小,离子通量则发生迅速衰减。在射频电极覆盖的范围内离子能量分布大体上保持不变,电极与侧壁的交界处,由于受到侧壁处径向电场的影响,离子能量分布略有不同。在放电装置的中心区域,入射到电极上的离子角度分布基本保持一致,而在电极边界与装置侧壁的交界处,由于径向电场的影响,离子的垂直入射角增加,以大角度轰击电极的离子数量也显著增加。     

CF_4/Ar/O_2等离子体对熔石英元件的修饰工艺

采用感应耦合等离子体刻蚀技术,以CF4/Ar/O2为反应气体对熔石英元件表面进行修饰,研究并分析了CF4和Ar流量对刻蚀速率、熔石英表面粗糙度和微观形貌的影响。结果表明,CF4化学刻蚀与Ar的物理轰击对熔石英样品表面修饰效果存在一定竞争关系,当它们达到平衡时表面粗糙度最小。通过对不同流量气体刻蚀过后熔石英表面粗糙度和光学显微形貌分析获得了较为理想的气流量配比,该研究为反应等离子体修饰熔石英光学元件以获得较高光学性能提供工艺参考。     

双频容性耦合CF4等离子体放电的二维混合模拟

研究了等离子体反应装置内的等离子体密度、粒子能量与角度分布等参量在装置径向与轴向上的分布特性。在研究过程中应用二维混合模型对CF4气体放电进行模拟。计算结果显示：在电极表面与侧壁附近的鞘层区特性有明显的区别。由于装置侧壁处受电源产生的射频电场的影响较小,侧壁处的鞘层主要由双极扩散机制形成,其产生的径向电场强度较弱,鞘层厚度也较薄。而在电极附近,由于受到射频电场的影响,鞘层的厚度显著增加,指向电极方向的轴向电场强度也远大于指向侧壁方向的径向电场强度。在电极区域内,离子通量分布均匀;在电极边缘与侧壁的间隙内,因电场强度减小,离子通量则发生迅速衰减。在射频电极覆盖的范围内离子能量分布大体上保持不变,电极与侧壁的交界处,由于受到侧壁处径向电场的影响,离子能量分布略有不同。在放电装置的中心区域,入射到电极上的离子角度分布基本保持一致,而在电极边界与装置侧壁的交界处,由于径向电场的影响,离子的垂直入射角增加,以大角度轰击电极的离子数量也显著增加。     

CF4/Ar/O2等离子体对熔石英元件的修饰工艺

采用感应耦合等离子体刻蚀技术,以CF4/Ar/O2为反应气体对熔石英元件表面进行修饰,研究并分析了CF4和Ar流量对刻蚀速率、熔石英表面粗糙度和微观形貌的影响。结果表明,CF4化学刻蚀与Ar的物理轰击对熔石英样品表面修饰效果存在一定竞争关系,当它们达到平衡时表面粗糙度最小。通过对不同流量气体刻蚀过后熔石英表面粗糙度和光学显微形貌分析获得了较为理想的气流量配比,该研究为反应等离子体修饰熔石英光学元件以获得较高光学性能提供工艺参考。     

Resonance dipole-dipole coupling and Fermi resonance in CF4 dimers

The FTIR spectra of Ar(Ne)/CF₄ matrixes have been recorded at matrix concentrations varying in the range 10 000-600 cm⁻¹. The absorptions due to the CF₄ monomers and to the (CF₄)₂ resonance dimers in the spectra of the two matrixes have been identified. The intramolecular Fermi resonance in the spectra of the CF₄ monomers trapped in solid argon and neon has been analyzed. The spectra of the (CF₄)₂ dimers are determined by the strong resonance dipole-dipole interaction of the two interacting molecules and by strengthening or weakening of the intramolecular Fermi resonance interaction.     

Relevance of polarization phenomena in an optically pumped CF4 laser

Some applications of polarization phenomena in an optically pumped CF₄ lasers are reported. It is shown that the performance of a CF₄ laser can be greatly improved when the polarization characteristics of its optical cavity are chosen according to the types of transitions involved in the optical pumping and emission processes. It is also shown that polarization phenomena can be used to obtain an indication of the type of pumping and lasing transitions.     

Experimental study on parameters of dust plasma in SiH4/C2H4/Ar discharges

Measurements of dust plasma parameters were carried out in the discharges of （SiH4/C2H4/Ar） mixtures. Dust particles were formed in the capacitively coupled radio-frequency discharge of these reactive mixtures in a cylindrical chamber. Langmuir probe was employed for diagnosing and measuring the important plasma parameters such as electron density and electron temperature. The results showed that the electron density dropped, and in contrast the electron temperature rose when the dust particles formed. The curves of the electron density and temperature versus the RF power and pressure were presented and analysed. Further, it was found that the wriations of electron temperature and the size of dust void with the RF power followed the similar trends. These trends might be useful for understanding more about the characteristics of dusty voids.     

10－5000 伏下电子被多原子分子CF4, CF3H, C2F4, C2F6, 及 C2H3F3散射总结面的计算

利用可加性规则和光学势方法计算了能量在10-5000 eV范围内电子被多原子分子CF4, CF3H, C2F4, C2F6, 及 C2H3F3的总结面，并与已有的实验结果和理论计算进行了比较，与这些结果符合得很好。对于CF4, CF3H, C2F4, C2F6, 及 C2H3F3在1000eV以上没有实验数据，本文对实验研究提供了对比和预测的数据。     

Li_4SiO_4陶瓷小球水解吸行为实验研究

采用程序升温热解吸(TPD/TDS)方法对Li4SiO4陶瓷小球的水解吸行为进行了实验研究。结果表明:水解吸过程中主要存在四个解吸峰;其中100℃附近的峰可解释为物理吸附水;150,250,400℃附近的峰可分别解释为以氢键、Li-OH和Si-OH配位键形式存在的化学吸附水。氚的释放与水的解吸几乎同步进行,且氚的释放形式主要为氚水(HTO),据此推测,氚水可能存在三种释放机制:(1)-OT+H2O→-OH+HTO;(2)-OH+-OH→H2O,-OT+H2O→-OH+HTO;(3)-OT+-OH→HTO。     

Li4SiO4陶瓷小球水解吸行为实验研究

采用程序升温热解吸（TPD/TDS）方法对Li4SiO4陶瓷小球的水解吸行为进行了实验研究。结果表明：水解吸过程中主要存在四个解吸峰;其中100 ℃附近的峰可解释为物理吸附水;150,250,400 ℃附近的峰可分别解释为以氢键、Li－OH和Si－OH配位键形式存在的化学吸附水。氚的释放与水的解吸几乎同步进行,且氚的释放形式主要为氚水（HTO）,据此推测,氚水可能存在三种释放机制：（1）－OT+H2O－OH+HTO;（2）－OH+－OHH2O,－OT+H2O－OH+HTO;（3）－OT+－OHHTO。     

Experimental study of stark broadening of nitrogen ion lines in a theta pinch plasma

We have studied the Stark broadening of the 3s-3p, 3p-3d and 3d-4f emission lines of the nitrogen II, III, and IV ions emitted from a hot plasma. The plasma was created by a 60 kJ, 60 kV single turn coil theta pinch, where the fill gas was 3 torr of (49%He+51%N₂). The plasma was diagnosed by measuring the Stark-broadened profile of the He(II) 4686 Å line and by taking shadowgrams of the plasma development. It was found that the ionization stage distribution and thus the electron density departed from that predicted by Saha-Boltzmann equilibrium relations. The analysis of the plasma parameters gave an electron density of 1.4 x 10¹⁸ cm^-3. The electron temperature was measured from the relative intensities of emission lines as well as from the line-to-continuum ratio and was found to be 5.0 eV. The line profiles have been fitted to Lorentzian profiles and the thus measure line widths are compared with earlier experimental data as well as with simple theoretical calculations. We find that our line widths are broader than earlier data taken at lower densities if we assume a linear scaling of the half width with the density. A simple Lorentzian profile fits in most cases quite well to the observed line profile. The simple calculations can predict the linewidths within 20% for the low lying levels of both the singly and doubly ionized nitrogen while the predictions are far too narrow for the higher lying levels from the multiply ionized atoms.     

克里奇中间体CH2OO与CF3CF=CF2反应的动力学研究

本文使用OH激光诱导荧光方法研究了结构最简单的克里奇中间体CH₂OO和CF₃CF=CF₂的反应动力学. 在压强为10 Torr条件下,测量了温度在283,298,308和318 K的反应速率常数,分别为(1.45±0.14)×10^-13,(1.18±0.11)×10^-13,(1.11±0.08)×10^-13和(1.04±0.08)×10^-13 cm³·molecule^-1·s^-1. 根据阿伦尼乌斯方程,获得该反应的活化能为(-1.66±0.21) kcal/mol. 在6.3∽70 torr压力范围内,未观察到该反应的速率常数存在压力相关.     

Vibrational spectra of H2O and CF4 molecules using Lie algebraic approach

In this paper, we introduce one dimensional vibron model to analyze the fundamental, overtone and combination modes of CF₄ molecule and both stretching, bending vibrational mode of bent H₂O molecule up to first overtone with few algebraic parameters. Using the model Hamiltonian, we reported here better results for the vibrational spectra of H₂O. Our analysis suggests some reassignments of levels and predicts location of states in case of CF₄ molecule which was not yet observed.     

Triply hydrogen bonded van der Waals complexes: CH2F2?CF2CH2 and CH2F2?CF2CHF

The results of molecular beam Fourier transform microwave (FTMW) investigations of the van der Waals complexes of difluoromethane with 1,1-difluoroethene (DFE) and trifluoroethene (TFE) are reported. The rotational parameters of the complexes have been interpreted in terms of a C_s geometry with the two H or F atoms of CH₂F₂ lying out of the σ_v symmetry plane of the complexes. The complexes are bound by three hydrogen bonds, of which one is the stronger C-F?H-C type, and two are the weaker C-H?F?H-C or C-F?H?F-C types for DFM-DFE or DFM-TFE, respectively. The most notable difference in the two complexes is that the out of plane atoms are two hydrogens for DFM-DFE, but are two fluorines for DFM-TFE. Additional information on the structure and hydrogen bonding has been obtained from ab initio calculations.