工作压强对射频辉光放电H2/C4H8等离子状态的影响

利用辉光放电技术采用等离子体质谱诊断的方法研究了不同工作 压强下H₂/C₄H₈混合气体等离子体中 主要正离子成分及其能量的变化规律, 并分析了压强对H₂/C₄H₈混合气体的离解机理以及主要正离子形成过程的影响. 结果表明: 随着工作压强的增加, 碳氢碎片离子的浓度和能量均逐渐减小. 当工作压强为5 Pa时, H₂/C₄H₈混合气体等离子体中C₃H₅⁺相对浓度最大; 压强为10 Pa时, C₃H₃⁺相对浓度最大; 压强为15, 20 Pa时, C₂H₅⁺相对浓度最大; 压强为25 Pa时, C₄H₉⁺相对浓度最大. 对H₂/C₄H₈等离子体中的主要组分及其能量分布所进行的定性分析, 将为H₂/C₄H₈混合气体辉光放电聚合物涂层的工艺参数优化提供参考技术基础. 关键词： 辉光放电技术 等离子体质谱诊断 工作压强     

Superconductivity in amorphous thin films of tin–copper

The properties of the superconducting state in the amorphous Sn_1?xCu_x thin films were characterized. The concentration of copper changes in the range from 0.08 to 0.41. The calculations were conducted in the framework of the strong-coupling formalism, wherein the Eliashberg functions determined in the tunnel experiment were used. The value of the Coulomb pseudopotential equal to 0.1 was adopted. It will be shown that the critical temperature (T_C) decreases from 7 to 3.9 K. The ratio, R_Δ = 2Δ(0)/k_BT_C, differs from the BCS value: R_Δ ∈ <4.4, 3.95>, where Δ(0) represents the order parameter. Similarly behave the ratios: R_C = ΔC(T_C)/C^N(T_C) ∈ <2.2, 1.75> and R_H = T_CC^N(T_C)/H²_C(0) ∈ <0.141, 0.154>. The parameter ΔC(T_C) is the specific heat jump, C^N(T_C) denotes the specific heat of the normal state and H_C(0) is the thermodynamic critical field.     

N2- and O2-broadening coefficients of C2H2 IR lines

Pressure-broadening parameters of six lines belonging to the ν₅ band of C₂H₂ in collision with N₂ have been measured with a tunable diode-laser spectrometer in order to complete up to J = 33 our earlier measurements (D. Lambot, G. Blanquet, and J. P. Bouanich, J. Mol. Spectrosc.136, 86–92 (1989)) on the broadening of C₂H₂ by N₂ and O₂ at 297 K. These N₂- and O₂-broadening coefficients have been first calculated on the basis of the Anderson-Tsao-Curnutte theory; in this approach, we show that the short-range interactions which contribute significantly to the linewidths are not correctly treated. Next, we consider the improved semiclassical model proposed by Robert and Bonamy. The intermolecular potential consists in the addition of the atom-atom interaction model to the quadrupolar interactions. The limited radial spherical harmonics expansion of the atom-atom potential, from which expressions for the differential cross section were derived, appears to be quite insufficient at short intermolecular distances. Therefore, we use a more accurate representation of this potential, avoiding an inadequate truncation and keeping the analytic expressions obtained by Bonamy and Robert. In the calculations we take into account the contributions derived from the radial functions U₀₀₀(r), U₂₀₀(r), and U₂₂₀(r), as well as from U₄₀₀(r). A theoretical expression is obtained for the U₄₀₀ contribution to the differential cross section. The results of the calculations arising from the exact radial expansion of the atom-atom potential appear to be significantly larger for high J lines than those arising from the truncated expansion. The latter results, which do not include adjustable atom-atom parameters, are in good agreement with experimental broadening coefficients for C₂H₂---O₂ and in reasonable agreement (except at large J values) for C₂H₂---N₂. It is also shown that the contributions to the linewidths derived from U₄₀₀ are rather small for C₂H₂---N₂ and more important for C₂H₂---O₂. Finally, by calculating the collisional linewidths of C₂H₂---N₂ and C₂H₂---O₂ at 200 K, we have predicted their temperature dependences.     

A study of molecular reorientation in a series of liquid n-alkanes using light-scattering spectroscopy

The spectra of the depolarized (VH) light scattered from the n-alkanes C₆H₁₄, C₈H₁₈, C₁₀H₂₂, C₁₂H₂₆, C₁₄H₃₀, C₁₅H₃₂ and C₁₆H₃₄ have been measured using a high resolution piezo-electrically scanned Fabry-Perot interferometer. The values of the molecular relaxation times τ _s derived from the spectra are compared with relaxation times τ _f derived from flow birefringence. The experimental results are discussed in terms of a phenomenological activation energy and also in terms of the coupling between the molecular reorientation and the hydrodynamic shear modes, allowing estimates of the strength of the coupling between these modes to be made.     

Synthesis and luminescence properties of lead-halide based organic–inorganic layered perovskite compounds (CnH2n+1NH3)2PbI4 (n=4, 5, 7, 8 and 9)

This paper describes the synthesis and characterization of organic–inorganic layered perovskite compounds, (C_nH_2n+1NH₃)₂PbI₄ (n=4, 5, 7, 8 and 9). The effect of the number of carbon atoms on luminescence properties has been examined. Thin films of microcrystalline (C_nH_2n+1NH₃)₂PbI₄ fabricated by spin-coating are highly oriented, with the c-axis perpendicular to the substrate surface. Temperature-dependent optical absorption spectra reveal that (C_nH_2n+1NH₃)₂PbI₄ films (n=4, 7, 8 and 9) show the structural phase transitions. The excitonic structures of (C_nH_2n+1NH₃)₂PbI₄ vary with the number of carbon atoms of the alkyl chain length. At low temperatures below 100 K, the lowest-energy free-exciton band of (C_nH_2n+1NH₃)₂PbI₄ (n=7, 8 and 9) split into three fine-structure levels. In contrast to (C_nH_2n+1NH₃)₂PbBr₄ films, (C_nH_2n+1NH₃)₂PbI₄ (n=7, 8 and 9) shows no triplet exciton emission, but it shows the Stokes-shifted emission from bound excitons.     

Synchrotron-radiation-induced deposition of boron and boron carbide films from boranes and carboranes II: Nido-2,3-diethyl-2,3-dicarbahexaborane

Boron-carbon thin films have been successfully deposited on Si (111) from the synchrotron radiation induced decomposition of the nido-2,3-diethyl-dicarbahexaborane, (CH₃CH₂)₂C₂B₄H₆. There are indications that molecular precursor states to complete dissociation exist, and that dissociation is the rate limiting step. As with deposition of boron from decaborane, there is an activation barrier to dissociation of diethylcarborane on Si (111). The composition of the growing film, as determined by the boron to carbon ratio, is strongly dependent upon the boron concentration at the surface of the substrate. The boron concentration of the film increases with increasing film thickness.Part one appeared in [1]     

LIF diagnostics of C2 radical behaviour in a laser CVD environment

A laser-induced fluorescence (LIF) system was developed to diagnose the reaction and transport of radicals in the ArF-laser-assisted CVD environment. The C₂(a ³ II _u) radicals were produced by the multi-photon dissociation of C₂H₂. The transport of the radical was directly measured by LIF. The disappearance rate of the radical in C₂H₂ was also determined. By using the values determined, the in-flux of the C₂ radicals onto a substrate was investigated, based on a diffusion model.     

E.P.R. study of γ-irradiated single crystals of K2C2O4.H2O and (NH4)2C2O4.H2O

The electron paramagnetic resonance of γ-irradiated single crystals of K₂C₂O₄.H₂O and (NH₄)₂C₂O₄.H₂O has been studied. The spectra show interesting microwave power saturation effects. The singlet spectrum is attributed to the C₂O₄ ^- radical derived from the C₂O₄ ^-- ion. The principal g-values are determined to be 1·998, 2·0028 and 2·0004. Certain weak lines are observed with different power saturation and interpreted as due to OH radicals derived from water molecules in the crystal lattice.     

Alternating magneto-birefringence of ionic ferrofluids in crossed fields

A dynamic probing of magnetic liquids is performed experimentally, using a static magnetic field modulated by another smaller field, normal and alternating. The optical magneto-birefringence under these crossed magnetic fields is recorded as a function of the frequency for different field intensities and different sizes of the magnetic nanoparticles. A general reduced behavior is found for the in-phase and the out-of-phase optical response which is well-described by a simple mechanical model. Depending on the value H _ani of the anisotropy field of the nanoparticles, we can distinguish two different high magnetic field regimes: - a rigid dipole regime (large anisotropy energy with respect to k _B T) for cobalt ferrite nanoparticles with a relaxation time inversely proportional to the field intensity H _C(H _C < H _ani), - a soft dipole regime (anisotropy energy of the order of k _B T) for maghemite nanoparticles with a relaxation time independent of the field intensity H _C(H _C > H _ani). Received 5 June 2000 and Received in final form 8 January 2001     

Phase diagram for diamond growth in atmospheric oxyacetylene flames

2 /C₂H₂ ratio for diamond synthesis in oxyacetylene flames can be theoretically predicted. When the substrate temperature is between 1000 K and 1250 K, the corresponding O₂/C₂H₂ ratio range is about between 0.8 and 1.1. The suitable range of substrate temperature is widest for O₂/C₂H₂ ratio close to unity and is narrowed rapidly when the flow ratio deviates from unity. Received: 2 March 1997/Accepted: 17 July 1997     

Study of the critical current density and the thermodynamic critical field in deuterated κ-(BEDT-TTF)2Cu[N(CN)2]Br organic superconductor

ABSTRACT

We have studied the reversible and irreversible part of the hysteresis loops as a function of slow cooling rate through the order–disorder transformation near 80?K for the deuterated (κ-D₈-Br) κ-(BEDT-TTF)₂Cu[N(CN)₂]Br organic superconductor. We estimated the critical current density J_C and the thermodynamic critical field H_C from the magnetic hysteresis loops. Temperature dependence of the critical current density derived from the irreversible part using Bean’s model. The thermodynamic critical field H_C has been obtained from the reversible part of the hysteresis loops.     

An ab initio potential energy surface for the C2H2–N2 system

An ab initio potential energy surface determined at the CCSD(T) level of theory is presented for the van der Waals complex C₂H₂–N₂. Additional calculations performed with the HF- and DFT- SAPT methods compare well with the CCSD(T) results and allow a better understanding of the main features of this interaction potential surface. An expansion of this surface over spherical harmonics has also been performed. The global energy minimum of the complex is obtained for the linear conformation. The T conformations are the least attractive. Such characteristics mainly arise because of the variation, in sign and in absolute value of the electrostatic energy between all these conformations. The specific role of the quadrupole–quadrupole interaction which involves two moments of opposite signs is therefore examined. The main features derived from the present surface are compared and discussed according to the following relevant systems: N₂–H₂, C₂H₂–H₂, C₂H₂–C₂H₂ and N₂–N₂. Calculated rotational constants for selected conformations of the C₂H₂–N₂ dimer are found to be in good agreement with available values.     

A hydrogen bonded complex C2H2…HBr isolated and characterized in the gas phase using pulsed-jet,Fourier transform microwave spectroscopy

A complex formed from ethyne and hydrogen bromide has been isolated and characterized by using a fast-mixing nozzle in conjunction with a pulsed-jet, Fourier transform microwave spectrometer. Any possible chemical reaction between the two components when mixed in the usual way was thereby precluded. The rotational constants A, B and C, the quartic centrifugal distortion constants δ_J, δ_Jk and δ_J and the Br nuclear hyperfine coupling constants X_aa and X_bb—X_cc (nuclear quadrupole) and M_bb (spin-rotation) were determined for each of the five isotopomers C₂H₂…H⁷⁹Br, C₂H₂…H⁸¹ Br, C₂H₂…D⁷⁹Br, C₂H₂…D⁸¹Br and C₂D₂…H⁷⁹Br. Interpretations of the spectroscopic constants show that the complex is planar and T shaped in the equilibrium conformation, with HCCH internuclear axis forming the cross of the T and the HBr internuclear axis lying along the C₂ axis of C₂H₂. The H of HBr is closer to the centre (?) of the π bond of ethyne, and therefore HBr is involved in a hydrogen bond to the π system, in which the distance of H from ? is r (?…H) = 2.469(1) A. The intermolecular stretching force constant is estimated as kσ = 5.38(2) Nm^?1 for the species involving a hydrogen bond (C₂H₂…H⁷⁹Br, C₂H₂…H⁸¹Br and C₂D₂…H⁷⁹Br) while this quantity increases to kσ = 5.68(2)Nm^?1 for those complexes bound through a deuterium bond (C₂H₂…D⁷⁹Br and C₂H₂…D⁷⁹Br). The opportunity is taken to consider similarities in the properties of complexes within the two series B…HBr and B…HC1 for a range of Lewis bases B, including B = C₂H₂. Some family relationships are identified in the two series.     

The structure of H2CSe from microwave spectroscopy

The microwave spectra of six isotopic species of selenoformaldehyde, H₂¹³C^78,80Se, D₂C^78,80Se, and DHC^78,80Se have been assigned. The resultant rotational constants, together with those of previous work yield the following substitution structure: r(C=Se) = 175.31 pm, HCH = 117.93°, and r(C---H) = 109.04 pm. This structure is compared with the equilibrium structure derived from ab initio calculations. The fundamental vibrational frequencies and centrifugal distortion constants of H₂C⁸⁰Se have been calculated.     

Flow birefringence and stress optical law of viscoelastic solutions of cationic surfactants and sodium salicylate

The optical and rheological properties of different viscoelastic solutions of surfactant are studied in order to gather experimental data used to calculate the value of the stress optical coefficient C. Three surfactants of the same family (CTAB) have been chosen; they differ by the length of the hydrocarbon chain; it concerns the dodecyltrimethylammonium bromide (C₁₅H₃₄BrN or DoTAB), the myristyltrimethylammonium bromide (C₁₇H₃₈BrN or MyTAB), and the hexadecyltrimethylammonium bromide (C₁₉H₄₂BrN or CTAB). Different parameters like the temperature of the solution and the salinity of the solvent have been made to vary. Flow birefringence experiments and rheological measurements are performed on these solutions in order to study the dependence of the extinction angle , of the birefringence intensity and of the shear stress with the shear rate . These data are used to check the stress optical law which turns out to be valid in a wide range of shear rates. The stress optical coefficient C is then computed: it is found to vary with the salinity of the solvent and the temperature of the solution for a given surfactant. Then, for all solutions of this work the variations of C are related to the variations of the polarizability anisotropy and the persistence length. Received: 18 February 1998 / Revised: 23 June 1998 / Accepted: 22 July 1998     

Selective optothermal detection of NO2 and H2O with a frequency-tuned CO waveguide laser

The results are reported of the CO-laser optothermal (OT) detection of impurity gases when their absorption spectra overlap with those of an interfering gas. The influence of the latter was avoided using low gas pressures corresponding to a maximum of the OT sensitivity. Frequency tuned in the 5.2–6.3 m wavelength range, ¹²C¹⁶O and ¹³C¹⁶O waveguide lasers were used. The fine frequency tuning at 490 MHz was achieved for 150 laser transitions of both molecules. The OT sensitivity was estimated by NO₂ detection in the presence of water vapor. The minimal detectable concentration proved to be 60 ppb at P _19–18(14) transition of a ¹²C¹⁶O laser for NO₂ and 75 ppb on P _12–11(13) transition of a ¹³C¹⁶O laser for H₂O.     

Comparative Plasma Chemical Reaction Studies of CH4/Ar and C2Hm/Ar (m = 2,4,6) Gas Mixtures in a Dielectric Barrier Discharge

Plasma chemical reactions in CH4/Ar and C₂H_m/Ar (m = 2, 4, 6) gas mixtures in a dielectric barrier discharge at medium pressure (300 mbar) have been investigated. From mass spectrometry the production of H₂ and formation of larger hydrocarbons such as C_nH_m with up to n = 12 is inferred. Hydrogen release is most pronounced for CH₄ and C₂H₆ gas mixtures. Fourier Transform InfraRed (FTIR) spectroscopy reveals the formation of substituted alkane (sp³), alkene (sp²), and alkyne (sp) groups from the individual gases which are used in this work. Abundant formation of acetylene occurs from C₂H₄ and to a lesser extent from C₂H₆ and CH₄ precursor gases. The main reaction pathway of acetylene leads to the formation of large molecules via C₄H₂ and, eventually, to nano‐size particles. The experimental results are in reasonable agreement with simulations which predict a pronounced electron temperature and gas pressure dependency. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Measurement of C2 and CH temperatures in argon‐acetylene low‐pressure microwave‐induced plasma

The emission spectra of C₂(d³Π_g–a³Π_u), CH(A²Δ–X²Π), and CH(B²Σ–X²Π) bands are analysed to measure rotational T_rot, vibrational T_vib, and gas temperature T_g from Ar/C₂H₂ (5–20% C₂H₂) microwave‐induced plasma (MIP). In case when helium and hydrogen are used in the gas mixture instead of argon, no significant change in T_rot is noticed. Both studied temperatures are insensitive in terms of the C₂H₂ percentage. From CH(0–0, A²Δ–X²Π) band R₂ branch lines, two T_rot (T_rot ～ 520–580 K for J′ = 3–9 and T_rot ～ 1,700–1,800 K for J′ = 10–17) are determined. The lower T_rot equals the T_g (500–700 K) measured from C₂ bands in this study. The H₂ Fulcher‐α diagonal bands are recorded as well in the H₂/C₂H₂ mixtures and T_rot～750–900 K of the H₂ ground state measured. T_vib ～ 6,000 K in Ar/C₂H₂ MIP is calculated from the integral intensity ratio of C₂(2,1) and C₂(3,2) bands.     

Growth of carbon nanotubes (CNTs) on metallic underlayers by diffusion plasma-enhanced chemical vapour deposition (DPECVD)

Here, we demonstrate the low-temperature (480–612 °C) synthesis of carbon nanotubes (CNTs) on different metallic underlayers (i.e., NiV, Ir, Ag, Pt, W, and Ta) using diffusion (dc) plasma-enhanced (~20 W, −600 V) chemical vapour deposition (DPECVD). The catalyst used is bi-layered Fe/Al and the feedstock used is a mixture of C₂H₂ and NH₃ (1:4). The crucial component is the diffusion of radical ions and hydrogen generated such as H₂/H⁺/H₂⁺/NH₃⁺/CH₂⁺/C₂H₂⁺ (which are confirmed by in-situ mass spectroscopy) from the nozzle, where it is inserted for most effective plasma diffusion between a substrate and a gas distributor.     

二硫酸-二元胺锰和二羟基-二元胺锰纳米片磁性的第一性原理研究

We perform first-principles simulations on a type of two-dimensional metal-organic nanosheet derived from the recently reported manganese bis-dithiolene Mn₃C₁₂S₁₂ [Nanoscale 5, 10404 (2013)] and manganese bis-diamine Mn₃C₁₂N₁₂H₁₂ [ChemPhysChem 16, 614 (2015)] mono-layers. By coordinating chalcogen (S or O) atoms and -NH- group to Mn atoms with trans- or cis-structures and preserving space inversion symmetry, four configurations of this type of nanosheet are obtained: trans-manganese dithiolene-diamine Mn₃(C₆S₃N₃H₃)₂, cis- manganese dithiolene-diamine Mn₃(C₆S₆)(C₆N₆H₆), trans-manganese dihydroxyl-diamine Mn₃(C₆O₃N₃H₃)₂, and cis-manganese dihydroxyl-diamine Mn₃(C₆O₆)(C₆N₆H₆). The ge- ometric con guration, electronic structure and magnetic properties of these metal-organic nanosheets are systematically explored by density functional theory calculations. The cal- culated results show that Mn₃(C₆S₃N₃H₃)₂, Mn₃(C₆O₃N₃H₃)₂ and Mn₃(C₆O₆)(C₆N₆H₆) monolayers exhibit half-metallicity and display strong ferromagnetism with Curie transition temperatures near and even beyond room temperature, and Mn₃(C₆S₆)(C₆N₆H₆) monolayer is a semiconductor with small energy gap and spin frustration ground state. The mechanisms for the above properties, especially in uences of diflerent groups (atoms) substitution and coordination style on the magnetism of the nanosheet, are also discussed. The predicted two-dimensional metal-organic nanosheets have great promise for the future spintronics ap-plications.