Showing papers in "Transactions of The Faraday Society in 1971"
TL;DR: The empirical dielectric decay function ϕ(t)= exp −(t/τ0)β, 0 0, but significant corrections may have to be applied for β > 0.5 and log ωτ0 < 0.
Abstract: The empirical dielectric decay function ϕ(t)= exp –(t/τ0)β, 0 0, but significant corrections may have to be applied for β >0.5 and log ωτ0 < 0.
431 citations
TL;DR: In this article, the triplet-triplet extinction coefficients of seventeen compounds have been determined in cyclohexane and benzene at room temperature by a method involving energy transfer, assuming no change of oscillator strength with solvent.
Abstract: The triplet-triplet extinction coefficients of seventeen compounds have been determined in cyclohexane and benzene at room temperature by a method involving energy transfer. Large changes in extinction coefficient at the wavelength maximum Iµ(λmax) were observed upon changing solvent from cyclohexane to benzene. Values of Iµ(λmax) were determined relative to a value of Iµ(λmax) for the ketyl radical (ϕ2ĊOH) of 3220 M–1 cm–1 in water, assuming no change of oscillator strength with solvent. A number of triplet transfer rates, and other reactivities of benzophenone triplet and ketyl radicals, were also estimated.
392 citations
TL;DR: In this paper, the equilibrium properties of liquid potassium chloride are simulated by a Monte Carlo model consisting of 216 particles interacting according to pair potentials of the form ϕ(r)=ar−1+b exp (−Br)−cr−6+dr−8 with constants derived from the properties of the solid at 298 K.
Abstract: The equilibrium properties of liquid potassium chloride are simulated by a Monte Carlo model consisting of 216 particles interacting according to pair potentials of the form ϕ(r)=ar–1+b exp (–Br)–cr–6+dr–8 with constants derived from the properties of the solid at 298 K.1 The internal energy, pressure, molar heat capacities, temperature coefficients of pressure and volume, compressibility and entropy, as well as radial distribution function, are computed for 24 V,T points lying on one solid phase (1045 K) and four liquid phase (1045, 1306, 2090, 2874 K) isotherms at pressures up to 5 kbar. The calculated quantities which include the normal melting point and some experimentally inaccessible data, are in good agreement with the available experimental results. The resolution of the radial distribution function into contributions from different types of ion pairs provides new information about the structure of the liquid salt.
233 citations
TL;DR: In this paper, a model for the surface structure of rutile is proposed, based on infra-red studies of a crystalline sample prepared by the combustion of Ti(iso-PrO)4.
Abstract: A model for the surface structure of rutile is proposed, based on infra-red studies of a crystalline rutile sample prepared by the combustion of Ti(iso-PrO)4. It is suggested that the exterior surfaces of the rutile crystals correspond to three low index crystal planes—namely the (100), (101) and (110). Of these the first two are capable of adsorbing molecular water as ligand coordinated to Ti4+ surface ions, whereas the (110) crystal face adsorbs water dissociatively leading to the presence of equal quantities of two types of OH– ions. One of these types is associated with a surface Ti4+ ion which is five coordinate with respect to lattice oxide ions whereas the other type is bound to a surface Ti4+ ion which is only four fold oxide ion coordinate. It is possible to rationalize the observed thermal dehydroxylation and dehydration properties of the oxide and also account for its pyridine adsorption properties.
166 citations
TL;DR: In this paper, the nature of oxygen adsorbed on slightly reduced TiO2 has been investigated using oxygen enriched with 17O2; no structure could be resolved for Ayy and Azz.
Abstract: The nature of oxygen adsorbed on slightly reduced TiO2 has been investigated using oxygen enriched with 17O2. On anatase, the oxygen adsorbs as O–2 with a hyperfine splitting Axx about g3 of 77 G; no structure could be resolved for Ayy and Azz. On rutile, oxygen adsorbs as O–2 on two sites of different thermal stability; (I) with g1= 2.030, g2= 2.008, g3= 2.004 and Axx= 76 G, and (II) with g1= 2.020, g2= 2.009, g3= 2.003 and Axx= 72 G. The evidence indicates that O–2 exists in a largely ionic form on TiO2 and other oxides. A symmetrical line at g= 2.003 which appears on some anatase samples after oxygen adsorption is attributed to the localization of a conduction electron by the adsorbed oxygen.
153 citations
TL;DR: In this article, the stretching vibrations of water in montmorillonite, hectorite, saponite and vermiculite are split into two components, similar to those seen in perchlorate solutions.
Abstract: The stretching vibrations of water (H2O, HDO and D2O) in montmorillonite, hectorite, saponite and vermiculite are split into two components, similar to those seen in perchlorate solutions. Examination of lower hydrates and pyridine complexes of the layer silicates shows that the higher frequency component corresponds to hydrogen bonds to oxygens of Si—O—Si linkages, the lower frequency component to water-water bonds and hydrogen bonds to oxygens of Al—O—Si linkages. The observations are explained in terms of chains of hydrogen-bonded water molecules which form dielectric links between interlayer cations and oxygens on the silicate anion surface. This concept, together with information obtained on the distribution of charge on the surface oxygens, provides a qualitative explanation of the hydration properties of layer silicates, and is extended to account for the stability of organic complexes of montmorillonite and hectorite. Some analogies between interlayer complexes and ionic solutions are proposed.
141 citations
TL;DR: The absolute density, thermal expansion coefficient α, and thermal pressure coefficient γ have been determined for atactic polystyrene in the nonglassy liquid (or amorphous) state as discussed by the authors.
Abstract: The absolute density, thermal expansion coefficient α, and thermal pressure coefficient γ have been determined for atactic polystyrene in the non-glassy liquid (or amorphous) state. Dilatometric measurements on the pure polymer furnished α over the range 100° to 230°C. Thermal pressure coefficients were determined by extrapolation from measurements on concentrated solutions of the polymer in benzene, from 24° to 100°C. No evidence was found for a second order transition above 100°C. A small change in dα/dT was observed near 170°C. This and other observations suggest a minor departure from equilibrium below this temperature.
137 citations
TL;DR: In this article, rotational correlation times for water molecules were evaluated in mixtures with mol fractions of water, x(H2O), ⩽0.7, interpreted in terms of end-over-end rotation of DMSO molecules and internal rotation of methyl groups.
Abstract: Spin-lattice (T1) and, where appropriate, tranverse (T2) relaxation times are reported for the protons in DMSO + water mixtures over a range of temperature and composition. Self-diffusion coefficients are also measured. A minimum in T1 for a d6-DMSO + H2O sample enables rotational correlation times for water molecules to be evaluated in mixtures with mol fractions of water, x(H2O), ⩽0.7. The low temperature (170-250 K) behaviour of T1 for DMSO + D2O mixtures with x(D2O)≃0.7 is interpreted in terms of end-over-end rotation of DMSO molecules and internal rotation of methyl groups. Under certain assumptions rotational correlation times for the DMSO molecules are obtained from the intramolecular contribution to T1 derived from measurements on ternary mixtures of the type d6-DMSO + DMSO + D2O. These are found to be very similar to those for the water molecules at the same temperature and compositions suggesting that the DMSO and water molecules reorient together. All measurements indicate a minimum in molecular mobility, both rotational and translational, at around a mol fraction of water of 0.65.
136 citations
TL;DR: In this paper, high-resolution photoelectron spectra of F2, Cl2, Br2, I2 and ICl are reported and interpreted in terms of the electronic structures of these molecules.
Abstract: High-resolution photoelectron spectra of F2, Cl2, Br2, I2, ICl and IBr are reported and interpreted in terms of the electronic structures of these molecules. Vertical and adiabatic ionization potentials as well as vibrational data are given for the ionized states arising from the removal of an electron from each molecular orbital. Where possible, these values are related to the emission spectra of the molecular ion and to the vacuum u.-v. spectra of the neutral species.
122 citations
TL;DR: In this article, the dielectric β relaxation of polyvinyl chloride has been studied in the ranges of temperature, pressure and frequency, 296 to 353 K, 1 × 105 to 3 × 108 N m 2 and 1 to 105 Hz.
Abstract: The dielectric β relaxation of polyvinyl chloride has been studied in the ranges of temperature, pressure and frequency, 296 to 353 K, 1 × 105 to 3 × 108 N m–2 and 1 to 105 Hz. Detailed results are discussed in terms of current concepts of the α, β and (αβ) relaxations which occur in amorphous polymers and in small molecule glass forming systems.
116 citations
TL;DR: In this paper, the decomposition of methyl alcohol on ZnO was studied using infra-red spectroscopy during the course of the reaction, and the concentrations and reactivities of the chemisorbed and gas phase species were measured as well as the overall reaction rate under various nonstationary conditions.
Abstract: The decomposition of methyl alcohol on ZnO was studied using infra-red spectroscopy during the course of the reaction. The concentrations and reactivities of the chemisorbed and gas phase species were measured as well as the overall reaction rate under various non-stationary conditions.
When CD3OD vapour was introduced over ZnO, methoxide ion and formate ion were observed, and D2, CO2 and CO were evolved into the gas phase. When the CD3OD in the ambient gas was removed by a dry ice-methyl alcohol trap during the course of the reaction, the evolution of D2 and CO2 stopped, while the evolution of CO continued unchanged. At 240°C, the decomposition rate of the surface formate ion was in reasonable agreement with the rate of production of carbon monoxide. On releasing the trapped methanol, the rates of formation of CO2 and D2 increased again, surface methoxide reappeared, and the concentration of the surface formate ion decreased correspondingly.
These results lead to the conclusion that CO was produced mainly by the decomposition of formate ion, and D2 and CO2 came from the reaction between CD3OD and DCOO(a).
TL;DR: In this paper, an infra-red study of the rutile surface has shown that hydroxyl groups and physisorbed water may be removed by thermal activation, and water vapour is readily chemisorbbed at room temperature to produce a reversible surface.
Abstract: An infra-red study of the rutile surface has shown that hydroxyl groups and physisorbed water may be removed by thermal activation, and water vapour is readily chemisorbed at room temperature to produce a reversible surface. A model for the surface based on the (110) plane of rutile has enabled interpretation of the spectra indicating two types of hydroxyl groups represented by bands at 3700 and 3670 cm–1 with the latter being the thermally labile species. The oxide shows strong retention of physically adsorbed water molecules at temperatures up to 300°C.
TL;DR: In this article, the far ultra-violet continuum of nitric oxide was assigned to the dimer by obtaining the following experimental evidence: (a) the intensity of the spectrum is proportional to [NO]2; (b) the possibility that the carrier may be some other known oxide of nitrogen was eliminated; (c) from the temperature dependence the enthalpy change accompanying dissociation was 2.24 (± 0.1 ) kcal/mol (100-140 K).
Abstract: The far ultra-violet continuum of nitric oxide was assigned to the dimer by obtaining the following experimental evidence : (a) the intensity of the spectrum is proportional to [NO]2; (b) the possibility that the carrier may be some other known oxide of nitrogen was eliminated; (c) from the temperature dependence the enthalpy change accompanying dissociation was 2.24 (±0.1 ) kcal/mol (100–140 K), in good agreement with 2.4 (±0.2) kcal/mol deduced from the dimer infra-red intensities4; (d) approximate upper and lower limits to the dissociation constant, and the temperature dependence, were consistent with Guggenheim's5 method of analyzing the second virial coefficients by means of the principle of corresponding states.
An absolute scale of dissociation constants was fixed from the excess of the reduced second virial coefficient at its normal boiling point, and the temperature dependence found spectroscopically. The dissociation energy of the dimer is 1.6 (±0.1) kcal/mol. Evidence for substantial population of excited states of the dimer at 300 K was discussed. The dimer continuum exhibits a maximum at 2050 A, and the oscillator strength of the system was recorded as 0.26.
TL;DR: In this article, the authors derived explicit expressions for the empirical quantities (relating them to the optical constants of the media and other system parameters) which are both reasonably simple and correct to second-order terms in the film thickness.
Abstract: Assuming an oriented molecular layer to behave optically as a homogeneous, uniaxial medium with its optic axis normal to the interface, such a system is treated theoretically to yield equations relevant to both specular reflectance and ellipsometric spectroscopy. Explicit expressions are derived for the empirical quantities (relating them to the optical constants of the media and other system parameters) which are both reasonably simple and correct to second-order terms in the film thickness. From ellipsometric measurements alone, it is not possible to distinguish between very thin uniaxial and isotropic films. However, data for a very thin non-absorbing uniaxial film on an absorbing substrate (e.g., a metal), if analyzed on the assumption of film isotropy, lead to an apparent absorption index for the film of the magnitude of the absorption index found for semi-conductors. A similar result is predicted for specular reflectance measurements, except that in that case the apparent optical constants of the film depend on the angle of incidence.
TL;DR: An alternative derivation of part of the Kirkwood-Buff theory of solutions, which uses essentially classical thermodynamic concepts, is presented in this article, which relates the thermodynamic properties of a solution to the integrals of the radial distribution functions of the various molecular pairs present.
Abstract: An alternative derivation of part of the Kirkwood-Buff theory of solutions, which uses essentially classical thermodynamic concepts is presented. This theory relates the thermodynamic properties of a solution to the integrals of the radial distribution functions of the various molecular pairs present. Useful expressions are derived for electrolyte solutions and for solutions of two and three components. Of particular importance are the general expression for the primary medium effect for a neutral electrolyte and the expression for the effect of one component on the solubility of another in a three component system, which shows how the theory can be used as a general basis for discussing hydrotropy and related phenomena.
TL;DR: In this paper, the decay of C(23PJ) has been monitored directly in the presence of a number of gases and the rate data for 300 K have been obtained.
Abstract: Time-resolved attenuation of the atomic emission transition C(33P°J→23PJ) at 166 nm has been used to study the reactions of C(23PJ). The decay of this atom, following its generation by the vacuum ultra-violet flash photolysis of carbon suboxide, has been monitored directly in the presence of a number of gases. The following rate data for 300 K have been obtained: C(23PJ)+ NO →CN + O, k= 7.3±2.2 × 10–11 cm3 molecule–1 s–1, C(23PJ)+ O2→CO + O, k= 3,3±1.5 × 10–11 cm3 molecule–1 s–1, C(23PJ)+ N2O →CO + N2, k= 2.5±1.6 × 10–11 cm3 molecule–1 s–1, or CN + NO, C(23PJ)+ H2O →CO + H2k⩽3.6 × 10–13 cm3 molecule–1 s–1, or CH2O, C(23PJ)+ CO2→2CO, k≤ 10–14 cm3 molecule–1 s–1, C(23PJ)+ CH4→C2H4, k < 2 × 10–15 cm3 molecule–1 s–1, C(23PJ)+ N2+ M →CN2+ M, k= 3.1±1.5 × 10–33 cm6 molecule–2 s–1(M = Ar), C(23PJ)+ H2+ M →CH2+ M, k= 7.1±2.5 × 10–32 cm6 molecule–2 s–1(M = He), C(23PJ)+ CO + M →C2O + M, k= 6.3±2.7 × 10–32 cm6 molecule–2 s–1(M = He).
TL;DR: In this article, it was shown that after outgassing at ambient temperatures the rutile surface carries both hydroxyl ions and adsorbed molecular water and that the depopulation of the surface caused by raising the outgas temperature follows a pattern that suggests there are two types of surface sites for the adsorbbed molecular species.
Abstract: Samples of rutile prepared by hydrolysis of TiCl4 and by combustion of Ti(isoPrO)4 have been investigated by infra-red spectroscopic techniques to provide information on their surface hydroxylation and hydration. After outgassing at ambient temperatures the rutile surface carries both hydroxyl ions and adsorbed molecular water. The depopulation of the surface caused by raising the outgassing temperature follows a pattern that suggests there are two types of surface site for the adsorbed molecular species. Complementary studies of pyridine adsorption indicate that the molecular water is held on the surface as a coordinating ligand and also show the presence of two types of hydroxyl species on the ambiently outgassed oxide. Further studies of the adsorption of thionyl chloride, sulphur dioxide and hydrogen chloride vapours support the contention that the surface hydroxyls are ionic in character. In the case of HCl adsorption, evidence for two types of coordinately bonded water was found after exposure of the oxide to the dry acid gas. It was also found that the sample prepared from TiCl4, which carried chlorine in its surface layers, was more readily dehydroxylated than the “chlorine free” material prepared from the metal alkoxide. The chlorine containing sample also aggregated on storage whereas the pure material did not.
TL;DR: In this article, the absolute intensity of dimole emission at 6340 A by two O21Δg was found to be 16±4 [O21 Δg]2 in cm3 mol−1 s−1 units.
Abstract: The absolute intensity of dimole emission at 6340 A by two O21Δg is found to be 16±4 [O21Δg]2 in cm3 mol–1 s–1 units. The rate constants for their energy pooling to yield O21Σ+g, ν= 0 and 1 are (1.2±0.3)× 107 and 6 × 105 cm3 mol–1 s–1 respectively. The removal of O21Σ+g at the walls is partly diffusion controlled, rate constants for its deactivation by H2O and H2 are reported.
TL;DR: In this paper, the angular distribution of scattered light during the rapid coagulation of polystyrene latex (diam. 126 nm) was measured at two wavelengths for times up to the half-life, and compared with those calculated from theory in which the number concentration of the aggregates were taken to be those given by von Smoluchowski's second-order kinetics and in which scattering properties of aggregates are described in terms of optical interference between their constituent primary particles.
Abstract: The changes occurring in the angular distribution of scattered light during the rapid coagulation of a polystyrene latex (diam. 126 nm) have been measured at two wavelengths for times up to the half-life, and compared with those calculated from theory in which the number concentration of the aggregates are taken to be those given by von Smoluchowski's second-order kinetics and in which the scattering properties of aggregates are described in terms of optical interference between their constituent primary particles. The agreement was good but absolute intensity measurements on the initial latex dispersion differed from those calculated from the Mie theory in a manner indicative of partial aggregation. When this was taken into account, excellent agreement between the measured and calculated angular distributions was obtained at all angles between 30 and 135° at both wave-lengths for times up to the half-life. The absolute rate constant for rapid coagulation was 67-69 % of the theoretical Smoluchowski value.
TL;DR: In this article, the authors measured the permittivity and loss of solutions of tri(n-butyl)ammonium picrate and iodide in various polar solvents at a number of frequencies between 0.2 and 3.0 GHz.
Abstract: The permittivity and loss of solutions of tri(n-butyl)ammonium picrate and iodide in various polar solvents have been measured at a number of frequencies between 0.2 and 3.0 GHz. The relative static permittivities of the pure solvents used range from 3.37 to 20.7 at 25°C. For all the solutions investigated, the observed dispersion of permittivity is adequately described by a single relaxation time, which for a given solvent depends on the concentration as well as the nature of the solute. Apparent dipole moments evaluated from the dispersion amplitude by means of Bottcher's theory, on the assumption that the dipole occupies a spherical cavity, are 12.3±0.4 D and 11.2±0.6 D for the picrate and iodide respectively. These values indicate that the relaxing dipole is an ion pair. Dielectric relaxation times corrected for internal field effects by different relations are compared with those calculated from the partial molar volume of the solute and the viscosity of the solvent by means of the Debye-Stokes equation. Density data for solutions of the two salts in 1,2-dichloroethane are included and from these data, partial molar volumes of the salts have been evaluated.
TL;DR: In this article, the authors investigated the process of solid phase transition, fusion and decomposition in several nitramines (and a nitrosamine) using differential scanning calorimetry.
Abstract: Processes of solid phase transition, fusion and decomposition in several nitramines (and a nitrosamine) have been investigated using differential scanning calorimetry. The following values (kcal mol–1) for the enthalpy changes, ΔH(TK) are reported: N-picryl-N-methylnitramine (tetryl), ΔHf(400.5)= 6.18±0.07, –ΔHd(445)= 94±2; 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX)ΔHf(478.5)= 8.52 ± 0.07, –ΔHd(483)= 136 ± 2; 1,3,5,7-tetranitro-1,3,5,7-tetra-azacyclooctane, (HMX), ΔHt,β→δ(ca. 460)= 2.35±0.20, –ΔHd(ca. 540)= 166±9; 1,7-diacetoxy-2,4,6-trinitro-2,4,6-triazaheptane (BSX), ΔHf(422.5)= 9.2 ±0.4, –ΔHd(ca. 500)= 124± 12; 1,5-endomethylene-3,7-dinitro-1,3,5,7-tetra-azacyclooctane (DPT), –ΔHd(ca. 471)= 35 ± 6; 1,3-dinitro-1,3-diazacyclopentane (DDCP), ΔHf(403)≃ 6.0; 1,3-dinitro-1,3-diazacyclohexane(DDCHX), ΔHt(343)= 3.7 ± 0.3, ΔHf(353)= 0.70 ±0.02; 1,3-dinitro-1,3-diazacycloheptane (DDCHP), ΔHt(370)≃ 5.6, ΔHf(376)≃ 0.95; 1,3,5-trinitroso-1,3,5-triazacyclohexane (TNOHX), ΔHt(365)= 4.25±0.15, ΔHf(376)= 0.90±0.03.
The depression of the melting point of tetryl caused by pre-heating the solids is used together with literature data ((i) relating the melting point depression with the amount of gas produced during decomposition, and (ii) for the amount of gas produced on complete decomposition) to calculate first-order rate constants for decomposition in the region of the solid→liquid transition. The results indicate a “premonitory” effect at temperatures below the melting point. With the exception of RDX (apparent Ea= 45.2±0.4 kcal mol–1) the apparent activation energies for de-composition of the nitramines tend to be unrealistically high. DDCHX, DDCHP and TNOHX show plastic crystal behaviour and may be classified as “globular” molecules; the absence of this type of behaviour with DDCP and RDX is discussed in terms of factors affecting molecular rotation in the solid state.
TL;DR: In this article, the energy component of the stress supported by the network is more or less independent of the network cure at a value of fe/f= 0.12±0.02.
Abstract: Thermoelastic measurements at constant volume are reported for a series of natural rubber samples. The energy component of the stress supported by the network is more or less independent of the network cure at a value of fe/f= 0.12±0.02. The energy component of the stress is independent of whether the measurements are made in the dry or in the swollen state, despite the fact that the dry rubbers have non-Gaussian equations of state and that the swollen rubbers approach Gaussian behaviour. Flory's analysis of rubber elasticity which includes hindered internal rotation in the main polymer chain, is compared with experimental results. To a first approximation it gives the correct order of magnitude for the energy component of stress. Measurements have also been made of the pressure coefficient of stress, from which the dilation coefficient of the rubber has been calculated as a function of strain. Flory's analysis does not appear to predict this coefficient satisfactorily.
TL;DR: In this paper, a technique of monochromatic flash spectroscopy with the resonance radiations of Xe (1470 A) and Kr (1236 A) is described, with a quantal absorption of 1.4 × 1014 quanta cm-3 per pulse.
Abstract: A technique of monochromatic flash spectroscopy with the resonance radiations of Xe (1470 A) and Kr (1236 A) is described, with a quantal absorption of 1.4 × 1014 quanta cm–3 per pulse. Production and decay of N2A3Σ+u(v= 0,1) was monitored photoelectrically from the sensitized fluorescence of either NO(γ-bands) or Hg (2537 A) line. Rate coefficients for deactivation of N2A3Σ+u were recorded as kHg= 2.9 × 10–10; kC2H2= 1.6 × 10–10; kC2H4= 1.1 × 10–10; kNO= 8.0 × 10–11; kNH3 < 2 × 10–11; kN2O= 6.1 × 10–12; kO2= 3.6 × 10–12; kn-C4H10= 2.7 × 10–12; kCO(N*2(v= 0))= 1.5 × 10–12, kCO(N*2(v= 1))= 2.4 × 10–11; kC3H8= 1.3 × 10–12; kC2H6= 3.6 × 10–13; and kH2= 3 × 10–15 cm3 molecule–1 s–1; a significant difference in the rates of deactivation of the v= 0 and 1 states of N2A3Σ+u was found only for CO. Except in the transfer to NH3 and Hg, the measurements agree well with those of Young et al.1–5
In high pressures of He, vibrational relaxation of N2A3Σ+u(v= 1) was induced by collision prior to its deactivation, and a rate coefficient of 1.2 × 10–15cm3 molecule –1 s–1 was recorded. Correlation of initial and final quantum states was achieved for the transfer to NO, which populates predominantly A2Σ+(v= 0 and 1) : N2A3Σ+u(v= 0)+ NOX2Π(v= 0)→ N2X1Σ+g+ NOA2Σ+(v= 1 : 0 = 1:9·5); N2A3Σ+u(v= 1)+ NOX2Π(v= 0)→ N2X1Σ+g+ NOA2Σ+(v= 1:0 = 1:1·9). The results were analyzed with a model in which the transition probabilities are proportional to the products of the two Franck-Condon factors and the mean density of states associated with particular reaction channels. Transfer from N2A3Σ+u to Hg populates directly the Hg(63P0) state to the extent of about 25 %. From a comparison of the simultaneous NO γ and Hg 2537 A emissions, it was suggested that excitation of NOA2Σ+ occurs with nearly unit efficiency. Excited atomic iodine (I52P½) was detected, via absorption of the 2060 A line by kinetic spectroscopy, in the deactivation of N2A3Σ+u by CH3I.
TL;DR: In this article, the profile of the occupied parts of the valence-band of elemental carbon in a number of distinct forms has been estimated by measuring the intensity of the photo-electrons emitted as a result of AlKα and MgKα irradiation.
Abstract: The profile of the occupied parts of the valence-band of elemental carbon in a number of distinct forms has been estimated by measuring the intensity of the photo-electrons emitted as a result of AlKα and MgKα irradiation. The widths of the bands for graphite (31 ± 2 eV), for diamond (33±3 eV), and for the less-ordered forms (carbonized poly-vinylidene chloride cellulose char, carbon fibre (PAN), vitreous carbon, powdered nuclear-grade graphite) are larger than expected theoretically, and on the basis of previous soft X-ray spectroscopic measurements. In line with recent views on the consequences of “amorphization”, it is established that the major part of the density-of-states curve is largely unaltered in going from the crystalline to the disordered solid. It is also established that the valence band of coronene is very similar to that of graphite.
Our measurements of the binding energies of core electrons yield two main conclusions: (i) the C1s binding energies in diamond and graphite are very similar, the respective values being 284.0 ± 0.3 and 284.3 ± 0.5 eV; (ii) chemisorption of oxygen at prismatic (but not at basal) faces of single-crystals of graphite is readily detectable from the O1s peak, the width of which indicates that at least two types of chemical linkages exist for the bound oxygen.
TL;DR: The transient absorption spectra observed on pulse radiolysis of neutral aqueous solutions containing p-benzoquinone and excess methanol, ethanol, isopropanol and formate, saturated with nitrous oxide are reported in this paper.
Abstract: The transient absorption spectra observed on pulse radiolysis of neutral aqueous solutions containing p-benzoquinone and excess methanol, ethanol, isopropanol and formate, saturated with nitrous oxide are reported. The spectra are analogous to those obtained in solutions containing excess t-butanol and N2, O2, nicotinamide adenine dinucleotide or thymine and are attributed to the semiquinone radical-anion formed by electron transfer reactions with bimolecular rate constants k=ca. 109-1010 M–1 s–1. This assignment is supported by measurements of the acid dissociation constant of the absorbing product (pKa= 4.1) in solutions containing excess acetone and isopropanol.
TL;DR: Differential heat of adsorption of water vapour on zeolites LiNaX, NaX, KNaX, RbNaX and CsNaX were measured calorimetrically over a wide range of adaption as mentioned in this paper.
Abstract: Differential heats of adsorption of water vapour on zeolites LiNaX, NaX, KNaX, RbNaX and CsNaX were measured calorimetrically over a wide range of adsorption. The heat of adsorption of water is determined mainly by the energy of specific interaction of the water molecules with the exchange cations, with the negatively charged oxygen ions of the zeolite framework, and with each other. The contributions of these interactions change with change of cation and with degree of filling; hence the dependence of the heat of adsorption of water on the amount adsorbed is wave-shaped in nature. This is due apparently to the presence of some groups of energetically different sites for water adsorption in the cavities of zeolites. Alternation of decrease and increase in the heat of adsorption of water with increasing coverage was particularly evident with KNaX zeolite. At low fillings the heats of adsorption of water decrease from LiNaX to CsNaX zeolites. Removal of Li+ by washing, sharply decreases the heat of adsorption of water at small coverages.
TL;DR: In this paper, the recombination coefficient, γ′H and the energy accommodation coefficient, βH were simultaneously determined for hydrogen atom recombination on Ag, Au, Co, Cu, W, Fe, Ni and Pt filaments.
Abstract: The recombination coefficient, γ′H and the energy accommodation coefficient, βH were simultaneously determined for hydrogen atom recombination on Ag, Au, Co, Cu, W, Fe, Ni and Pt filaments. Values of βH of 0.87, 0.65 and 0.43 were observed for Ag, Au and Cu, respectively, while values between 0.08 and 0.28 were observed for the other metals. In general, the relative values of βH for these filaments were similar to the values of β previously determined for oxygen atom recombination.
TL;DR: In this paper, the specific adsorption of fluoride ion on mercury has been studied at two temperatures, and a Freundlich-type isotherm describes the surface pressure of the adsorbed ionic film.
Abstract: The specific adsorption of fluoride ion on mercury has been studied at two temperatures. The unusual adsorption isotherm of the fluoride ion has been analyzed in terms of the equilibrium conditions prevailing across the double layer; a Freundlich-type isotherm describes the surface pressure of the adsorbed ionic film. The inner layer capacitance has been analyzed and its various components calculated, and from the variations of the inner layer capacitance at constant amount of adsorbed charge, the inner layer capacitance in the absence of adsorption has been evaluated. The anodic hump in the capacitance of fluoride solutions is due mainly to the adsorption of F– ions, and not to adsorbed solvent reorientation. The adsorption of SiF2–6 does not lead to a large increase in the double-layer capacitance at anodic potentials.
TL;DR: In this article, the planarity of both isomers has been accurately established on the basis of the inertial defects and quadrupole coupling constants at nitrogen have been determined for both the cis and trans isomers.
Abstract: Microwave spectra for eight isotopic species of cis and trans nitrous acids are reported. The planarity of both isomers has been accurately established on the basis of the inertial defects. Accurate structures, electric dipole moments and quadrupole coupling constants at nitrogen have been determined for both isomers. The structure of cis nitrous acid is found to be: O—H = 0.982, N—O(H)= 1.392, N—O = 1.185 A, ∠ NOH = 104.0 and ∠ ONO = 113.6°, and for trans nitrous acid: O—H = 0.958, N—O(H)= 1.432, N—O = 1.170 A, ∠ NOH = 102.1 and ∠ ONO = 110.7°. Stark effect measurements yield the following values for the components of the dipole moment for cis nitrous acid: µa= 0.306, µb= 1.389 and the total dipole moment µ= 1.423±0.005 D. Previous investigations of the Stark effect in the trans isomer have been refined to give µa= 1.378, µb= 1.242 and µ= 1.855±0.016 D. Orientation of the dipole moment has been established for both isomers from isotopic measurements, despite a moderately large vibrational change in µa for trans DNO2. Quadrupole coupling constants in the principal inertial axis system have been determined for cis nitrous acid to be: χaa= 2.05, χbb=–5.83 and χcc= 3.78 MHz, and for trans nitrous acid: χaa= 1.73, χbb=–5.28 and χcc= 3.55 MHz.
The structural parameters are markedly different in the two isomers and have been discussed, together with the torsional barrier and relative stability of the isomers, in terms of a cis interaction. The structures and charge properties of the nitrous acids are compared with a range of related compounds.
TL;DR: In this paper, the authors measured the internal rotation of the methyl group from splittings of the microwave lines for each compound and established the cis ester molecular skeleton for the latter four compounds.
Abstract: The stable molecular conformations of methyl-fluoroformate, -propiolate, -cyanoformate, -acrylate (cis) and -acetate have been shown to be planar, and for the latter four compounds the cis ester molecular skeleton has been established. Barriers to internal rotation of the methyl group were measured from splittings of the microwave lines for each compound. [XCOOCH3; X = F, V3= 1077; X = HCC, V3= 1266; X = CN, V3= 1172; X = CH3, V3= 1215; X = CH2CH, V3= 1220 (values of V3 in cal/mol).] For methyl acetate a value of 307 ± 50 cal/mol for the acetyl methyl group was calculated from internal rotation splittings in the spectrum of CD3COOCD3. The dipole moments of methyl-fluoroformate and cyanoformate were 2.83 and 4.23 D respectively.