Infrared combination bands of CH4 in crystal fields

Overtone and combination bands were observed between 1000 and 5000 cm^–1 for CH₄ molecules in several crystal fields: solid phases I and II, and diluted alloys with Kr. In the anisotropic field of phase II, a full (rotation/libration)-vibration spectrum was observed in the combination bands 2v ₄,v ₂+v ₄, andv ₃+v ₄. Here, all lines could be assigned to transitions of either D_2d or O_h molecules. The structure ofv ₃–v ₄,v ₂+2v ₄,v ₁+v ₄,v ₂+v ₃ and 3v ₄ bands could not be resolved. In phase I, all spectra show the characteristic features of rotational diffusion, while in a Kr matrix a rotovibrational structure could again be observed in the overtone and combination bands.     

The scattering of He from adsorbed layers of gases on Ag(110)

The adsorption of gases on Ag(110) has been studied using inelastic He atom scattering. Vibrational spectra have been obtained for Kr, Xe, C₂H₆, C₂H₄, CH₄, CF₄, CHF₃, CO₂ and H₂O. Spectra have also been obtained for multilayers of Xe (2 layers) and C₂H₆ (3 and 4 layers) where the energy changes move to lower values. The scattering from Kr and Xe can be shown to be dispersionless as has been previously found for these adsorbates on Cu(100) and Cu(110). The energy changes for Kr and Xe are smaller than on Cu surfaces and attempts were made to account for this based on an Einstein model of the adsorbed atoms in the surface holding potential.     

Inelastic atom scattering from layers of atoms and molecules on Cu(110)

The vibrational properties of adsorbed layers have been studied using inelastic He atom scattering. The substrate was Cu(110) viewed along the [001] and [11̄0] azimuth. The adsorbates included, Kr, Xe, CH₄, CD₄, C₂H₆, CO, CO₂ and O₂ and covered the region of both physisorption and chemisorption. Despite a range of binding energies and mass ratios the vibrational frequencies showed no dependence on the momentum change, i.e. scattering was dispersionless, although intensity changes occurred in the inelastic peaks. There seemed to be no dependence of the adsorbate spectra on coverage below a monolayer. The peaks of CH₄ and C₂H₆ appeared broader than those of Kr and Xe suggesting molecular motions. Further, CH₄ and C₂H₆ gave very similar spectra. Both energy gain and loss events were observed in the inelastic spectrum. For those adsorbates which gave multilayer adsorption (Xe, C₂H₆) changes in the spectra were observed as the second layer developed. In the latter category also, mixed layers (Xe on C₂H₆, Xe on CO and C₂H₆ on Xe) were studied.     

P.E.HSQC: a simple experiment for simultaneous and sign-sensitive measurement of (1JCH+DCH) and (2JHH+DHH) couplings

The angular information content of residual dipolar couplings between nuclei of fixed distance makes the accurate and sign-sensitive measurement of (¹J_CH + D_CH) and (²J_HH + D_HH) couplings highly desirable. Experiments published so far are typically highly specialized for the effective measurement of a subset of couplings. The P.E.HSQC presented here, is an E.COSY based experiment which allows the simultaneous measurement of all heteronuclear and homonuclear couplings within CH, CH₂, and CH₃ groups in a single spectrum with the necessary precision and sign information. The simplicity of the approach and the absence of artefacts like phase distortions due to antiphase evolution make it ideally suited for coupling determination of organic molecules at natural abundance.     

Experimental determination of the potential energy curves of the I(3/2u) and I(3/2g) states of Kr+ 2

The I(3/2u) and I(3/2g) states of Kr⁺ ₂ have been investigated by pulsed-field-ionization zero-kinetic-energy (PFI-ZEKE) photoelectron spectroscopy following (2 + 1′) resonance-enhanced multiphoton excitation via the 0⁺ _g Rydberg state located below the Kr?([4p]⁵5p[1/2]₀) + Kr(¹S₀) dissociation limit of Kr₂. From the positions of a large number of vibrational bands in the spectra of the ⁸⁴Kr₂ and ⁸⁴Kr-⁸⁶Kr isotopomers, the adiabatic ionization potentials (IP(I(3/2u)) = 112672.4 ± 0.8cm^?1, IP(I(3/2g)) = 111 395.0 ± 1.4cm^?1), the dissociation energies (D ⁺ ₀(I(3/2u)) = 368.8 ± 2.0cm^?1, D ⁺ ₀(I(3/2g)) = 1646.2 ± 2.3cm^?1) and vibrational constants for both ionic states have been determined. Potential energy curves have been extracted which perfectly reproduce all experimental observations and are accurate over a wide range of energies and internuclear distances. The equilibrium internuclear distances (R ⁺ _e(I(3/2u)) = 4.11 ± 0.04 Å, R ⁺ _e(I(3/2g)) = 3.35 ± 0.10 Å) have been derived by comparing the intensity distribution in the PFI-ZEKE photoelectron spectra to calculated Franck-Condon factors. The dissociation energy of the I(3/2g) state and the equilibrium internuclear distance of the I(3/2u) state differ markedly from previously reported values.     

Excess Gibbs energy for six binary solid solutions of molecularly simple substances

In this paper we apply the method developed in a previous study of Ar + CH₄ to the evaluation of the excess Gibbs energy G^{E S} for solid solutions of two molecularly simple components The method depends on combining information on the excess Gibbs energy G^{E L} for the liquid mixture of the two components with a knowledge of the (T, x) solid-liquid phase diagram Certain thermal properties of the pure substances are also needed G^{E S} has been calculated for binary mixtures of Ar + Kr, Kr + CH₄, CO + N₂, Kr + Xe, Ar + N₂ and Ar + CO. In general, but not always, the solid mixtures are more non-ideal than the liquid mixtures of the same composition at the same temperature Except for the Kr + CH₄ system, the ratio $\text{r =}\text{G}{}^{\mathrm{E\; S}}\text{G}{}^{\mathrm{E\; L}}$ is larger the richer the solution in the component with the smaller molecules     

Catalytic effect of water,water dimer,water trimer,HCOOH, H2SO4, CH3CH2COOH and HN(NO2)2 on the isomerisation of HN(NO2)2 to O2NNN(O)OH: a mechanism study

In this article, the isomerisation mechanisms of HN(NO₂)₂ to O₂NNN(O)OH without and with catalyst X (X = H₂O, (H₂O)₂, (H₂O)₃, HCOOH, H₂SO₄, CH₃CH₂COOH and HN(NO₂)₂) have been investigated theoretically at the CBS-QB3 level of theory. Our results show that the catalyst X (X = H₂O, (H₂O)₂, (H₂O)₃, HCOOH, H₂SO₄ and CH₃CH₂COOH) shows different positive catalytic effects on reducing the apparent activation energy of the isomerisation reaction processes. Such different catalytic effects are mainly related to the number of hydrogen bonds and the size of the ring structure in X (X = H₂O, (H₂O)₂ and (H₂O)₃)-assisted transition states, as well as different values of pK_a for H₂SO₄, HCOOH and CH₃CH₂COOH. Very interesting is also the fact that H₂SO₄-assisted reaction is the most favourable for the hydrogen transfer from HN(NO₂)₂ to O₂NNN(O)OH, due to the smallest pK_a (?3.0) value of H₂SO₄ than H₂O, HCOOH, H₂SO₄ and CH₃CH₂COOH, and also because of the largest ∠X???H???Y (the angle between the hydrogen bond donor and acceptor) involved in H₂SO₄-assisted transition state. Compared to the self-catalysis of the isomerisation mechanisms of HN(NO₂)₂ to O₂NNN(O)OH, the apparent activation energy of H₂SO₄-assisted channel also reduces by 9.6 kcal?mol^?1, indicating that H₂SO₄ can affect the isomerisation of HN(NO₂)₂ to O₂NNN(O)OH, most obvious among all the catalysts H₂O, (H₂O)₂, (H₂O)₃, HCOOH, H₂SO₄, CH₃CH₂COOH and HN(NO₂)₂.     

三甲基镓在Pd(111)表面吸附解离及表面预吸附H和O的影响

利用X-射线光电子能谱（XPS）和程序升温脱附谱（TPD）研究了三甲基镓在Pd（111）表面的吸附和解离行为,并考察了表面预吸附H和O的影响。结果表明,在吸附温度为140 K时,三甲基镓在Pd（111）上主要为解离吸附,此时表面物种为Ga（CH₃）_x （x=1,2,3）和CH_x物种。加热将导致Ga的甲基化合物中的Ga-C键发生分步断裂,在不同温度下产生CH₄和H₂从表面脱附。同时,XPS结果证实了在275~325 K的温度区间内存在Ga甲基化合物的分子脱附。退火至更高温度,表面只观察到积碳和金属Ga物种,这二者随着温度的继续升高逐渐向体相扩散。在Pd（111）表面预吸附O和H对上述吸附和解离行为存在显著的影响。当表面预吸附H时,脱附产物CH₄和H₂的脱附主要位于315 K,可归属为一甲基镓的解离脱附。当表面预吸附O时,只在258 K观察到CH₄和H₂的脱附峰,可能来自于Pd-O-Ga（CH₃）₂吸附结构的解离.     

EELS of methane physisorbed on NaCl(100)

EELS spectra of CH₄, CD₄ and CH₂D₂ physisorbed on NaCl(100) at 40 K are presented. For the clean NaCl surface, increasing the incident beam energy to the 30 to 50 eV range is sufficient to overcome charging effects. However, when adsorbate is present charging prevents extended signal averaging. All methane modes appear to contribute to the EELS spectra. Loss peaks corresponding to adsorbate vibrations are very broad (400 to 600 cm⁻¹, FWHH), the low resolution being probably due to a combination of effects including surface disorder, scattering of electrons by gas phase molecules and charging effects.     

Generation of intense pulsed low-kinetic-energy molecular beams

A method for the generation of intense pulsed low-kinetic-energy molecular beams is described. The method is based on the formation of a cold (≈77 K) pressure shock as a result of interaction between an intense pulsed gas-dynamically cooled molecular beam with a solid surface. The pressure shock is used as a source of a secondary beam for generating low-energy molecules. The suggested method was used to obtain intense molecular beams of H₂, He, CH₄, N₂, and Kr with kinetic energies lower than or equal to 10 meV and H₂/Kr and He/Kr molecular beams with kinetic energies of H₂ and He molecules lower than 1 meV. The energy (velocity) of molecules in low-energy beams can be controlled by varying the intensity of the initial beam or temperature in the pressure shock.     

The centrifugal distortion constant DK of symmetric top molecules

The centrifugal distortion constant D_K of a symmetric top molecule has proved a very elusive parameter to estimate by spectroscopic analysis. Values of D_K have been calculated for the molecules BF₃, SO₃, NH₃, PH₃, AsH₃, NF₃, PF₃, AsF₃, CH₃D, SiH₃D, GeH₃D, CH₃F, CH₃Cl, CH₃Br, CH₃I, CH_eCN, CH₃CCH, H₂C₃H₂, cyclo-C₃H₆, and isotopic modifications thereof, in terms of their quadratic force constants. In all cases the force constants used are reliably determined by existing spectroscopic data. Where direct comparison is possible, good agreement with experimental D_K values is found, and the calculated constants are considered reliable to ± 5%. The constants are intended to be of assistance in future spectroscopic and structural studies on the molecules listed. Structural applications to methyl iodide, silane, and cyclopropane are considered.     

SU(2)L×SU(2)R×U(1) gauge model

We determine here the most general electroweak interaction based on the groupSU(2)_L×SU(2)_R×U(1). When we rotate theZ ₁,Z ₂ basis to theZ,D basis such that the total interaction ofZ with the right-handed current is zero, we obtain an interaction that is free of triangle anomalies. This condition enables us to know the angle through whichZ ₁,Z ₂ basis is to be rotated. We show that the triangle anomaly free interaction obtained by others is contained here as a special case. We also determine the triangle anomaly free weak interaction whenever the neutral (Z,D) bosons are mass eigenstates and show that it reduces to the neutral sector of the standard model whenever g _R ² goes to infinity. The charged sector is also developed here. The most general elements of the masssquared matrix of theZ,D bosons are evaluated. The masses of the left- and right-handed charged bosons are also determined.     

Phase transitions in [NH(CH3)3]2MeCl4 (Me = Cd,Zn,Cu) crystals

Dielectric properties of the new [NH(CH₃)₃]₂ZnCl₄ and [NH(CH₃)₃]₂CdCl₄ crystals from the [(CH₃) _n NH_4-n ]₂MeCl₄ group have been investigated in a wide temperature range (4.2–320 K). A series of phase transitions has been discovered at T₃ = 325 K,T₄ = 251 K,T₅ = 193 K, for [NH(CH₃)₃]₂CdCl₄ and at T₃ = 309 K, T₄ = 282 K, T₅ = 269 K for [NH(CH₃)₃]₂ZnCl₄. A ferroelectric phase has been discovered in the temperature interval T₄—T₅ from the temperature and frequency dependence of the dielectric permittivity ε(T, v). According to optical investigations the existence of ferroelastic phases in the temperature interval T₁ = 349 K–T₂ = 391 K and below T₅ for [NH(CH₃)₃]₂CdCl₄ and both above T₃ and below T₅ for [NH(CH₃)₃]₂ZnCl₄ has been ascertained.     

Proton and deuteron magnetic resonance of methanes,silanes and GeH3D dissolved in nematic liquid crystals

The proton and deuteron magnetic resonance spectra of CH₄, CH₃D, CH₂D₂, CHD₃, CD₄, SiH₄, SiH₃D, SiH₂D₂, SiH₃D, SiD₄, GeH₃D, dissolved in nematic liquid crystals, are reported. It was found that these molecules, which are essentially tetrahedral, exhibit anisotropic interactions and are partially oriented in the nematic phase. This effect is presumably due to slight deformations induced by the anisotropic medium. Some of the aspects related to the interpretation of the results are discussed.     

Rotational relaxation of symmetric tops CH3D and CD3H in some inert liquids

Infra-red spectra of CH₃D and CD₃H dissolved in liquid Ar, Kr, Xe, N₂, O₂ and CH₄ or CF₄ have been recorded. From the band shapes, rotational correlation functions, band moments and intermolecular mean square torques have been calculated. To describe the tumbling motion, involved in the parallel band profiles, we have computed the theoretical correlation functions in the m or j diffusion limits. The validity of these Gordon models is discussed. In an attempt to obtain some information on the rotational diffusion tensor, experimental correlation times have been estimated from A₁ and E bands of CD₃H.     

The anharmonic force field and equilibrium structure of methane

The anharmonic force field of methane has been refined to fit spectroscopic data from the isotopic species ¹²CH₄, ¹³CH₄, ¹²CH₄, ¹²CH₃D, ¹²CHD₃ and ¹²CH₂D₂. Six of the thirteen cubic force constants have been determined experimentally, the remaining cubic constants being fixed at values derived from ab initio calculations. The quartic force field is very crude, in that only f_rrrr has been refined. It is concluded however that the cubic and quartic force fields, even though they are subject to limitations, provide a considerable improvement in the experimental determination of the r _e structure and the quadratic force field. The equilibrium bond length is found to be r _e(CH) = 1·085₈ ± 0·001 Å.     

Generating intense beams of low-energy molecules

A method for obtaining intense pulsed beams of molecules possessing low kinetic energies is proposed. The method is based on the formation of a cold pressure shock (shock wave) in an intense pulsed molecular beam interacting with a solid surface, which serves as a source of the secondary beam of low-energy molecules. The proposed method was successfully used to obtain intense beams of H₂, He, CH₄, and Kr molecules with kinetic energies not exceeding 10 meV, and H₂/Kr and He/Kr beams with kinetic energies of H₂ and He molecules below 1 meV.     

FTIR and 1H NMR Spectral Study of 3-(Substituted Benzamido)-5,6,7,8-Tetrahydro-5,8-methanoiso-quinolines And Related Compounds

The title benzamide derivatives were synthesized. FTIR spectra of the benzamides having substituents p-NH₂, p-OCH₃, p-CH₃ 3, p-F, H 5,p-CI, p-CF₃, p-CN, p-NO₂ 9 and m-Cl 10 and their related compounds were measured in dilute n-heptane, CCl₄, CHCl₃ and CH₂Cl₂ solutions. ¹H NMR spectra of the benzamides were also measured in CDCl₃ solution. Substituent effects on these spectra were investigated. The results were theoretically considered together with CNDO/2 calculation ones. Conformational analysis of 5 was carried out by the AMl method, and the results were compared with the X-ray structural data of 3, 5, 9 and 10. The intermolecular hydrogen bondings in crystals of the benzamides were examined based on the frequency shifts of their C=0 stretching vibration bands.     

Proton spin-lattice relaxation of a tunnelling CH2D2 molecule

The proton spin-lattice relaxation time of a CH₂D₂ molecule is calculated. The tunnel splittings are assumed to be much larger than the Zeeman energy. The dependence of the relaxation efficiency on the site symmetry is examined. The results are compared with experimental T₁ values in the solid phases of CH₂D₂. Contrary to CH₄ and CD₄, the symmetry of the crystal field has no influence on the relaxation rate. The calculated relaxation rate is lower than experimentally observed, which indicates that some of the energy levels coincide.     

Triple differential cross-sections for near threshold (e, 2e) process for hydrogen

The resonance Raman (RR) spectra of nickel octaethyl porphyrin, Ni(OEP), in CH₂Cl₂ (solvent) at different excitations such as 514.5, 488.0, 441.6 and 406.7 nm are recorded and analysed. The results of the theory of distortion-induced RR intensity is applied to the observed spectra to determine the excited electronic state symmetry of porphyrin in Ni(OEP). It is concluded that the porphyrin molecule (D_4h structure) attains a non-polar distorted structure of D₂ symmetry rather than S₄ symmetry in CH₂Cl₂ solution.