Depth distribution of the fluorine concentration during radiative carbonization of PVDF

The XPS integral intensity of the F1s line and its satellite is measured during the long-term radiative carbonization of PVDF (polyvinylidene fluoride). A model is proposed that describes the effect of the fluorine depth distribution on the shape and intensity of the F1s spectra. A comparison of the experimental data with the model calculations provides estimates for the concentration inhomogeneity during the radiative carbonization of PVDF, for the photoelectron escape depth, and for the probability of a single energy loss by a photoelectron in its motion towards the surface. A technique determining the fluorine concentration is presented. It is based on the occurrence of chemical shifts of the C1s line towards larger bond energies for the carbon atoms chemically bonded to one or two fluorine atoms.     

Inhomogeneous depth distribution of fluorine atoms in PVDF upon radiative carbonization

Under the action of ionizing radiation on a PVDF film, fluorine and hydrogen atoms bound to its linear carbon chain with single chemical bonds detach. Free atoms and HF molecules diffuse toward the film surface and escape from it. As a result of irradiation of the sample surface, a fluorine concentration depth profile arises. The fluorine distribution in the PVDF films subjected to long-term X-ray exposure was studied using X-ray photoelectron spectroscopy and Rutherford backscattering spectroscopy. Both methods yield close values of the fluorine concentration at a depth of ～10 nm.     

On the radiative cooling of a surface during dew formation

Summary From the energy balance of a radiant surface with zero mass and perfectly insulated from below, the equilibrium temperature is calculated as a function of both sensible and latent heat transfer resistance. Under the hypothesis of Robinson,r _L=r _H is the air in contact with the surface is saturated, the equilibrium temperature is estimated as a function of air temperature, dew temperature and wind speed. This result could be useful to calculate night-time temperature of passive solar collectors or the yield of dew collectors. Paper presented at the 1^o Congresso del Gruppo Nazionale per la Fisica dell'Atmosfera e dell'Oceano, June 19–22, 1984, Rome.     

On the possibility of measuringF L (x,Q 2) at HERA using radiative events

It is shown that a significant measurement of the longitudinal structure functionF _L (x, Q ²) can be performed at HERA, forQ ²=2 GeV² andQ ²=5 GeV² and forx around 10^?4, using radiative events with hard photon emission collinear to the incident lepton beam, under the present running conditions and with an integrated luminosity of 10 pb^?1. The influence of experimental conditions is discussed.     

Approximate solutions of radiative transfer in one-dimensional non-planar systems

An approximate method is developed for the study of radiative transfer in one-dimensional, non-planar systems. While this method can be regarded as an extension of some existing approximation techniques formulated for the one-dimensional planar problem, it does yield closed-form expressions for the radiant heat flux and the temperature profile for various non-planar problems, which have not been established before. Comparisons with the available numerical results show that the heat-flux expressions are accurate throughout the entire range of the optical thickness. Results for the temperature profile. however, have the same limitation as the various closed-form approximate solutions for the planar problem. They are not very accurate at regions near the boundary, except in the optically thick limit. Based on the closed-form expressions obtained for the non-planar radiative transfer problem, the present work establishes readily the effect of the various parameters, such as the optical thickness, the surface emissivity, the radius ratio and the heat-generation rate on the heat-transfer and the temperature profile. Differences between radiative heat-transfer characteristics of the two basic non-planar systems (concentric cylinders and concentric spheres) are discussed.     

On the possibility of single-electron transfer during alkaline hydrolysis of sulfophthalides

The previously observed generation of radical products during the alkaline hydrolysis of diphenylsulfophthalide (DPSP) and polydiphenylenesulfophthalide in dimethyl sulfoxide (DMSO) is indicative of the involvement of single-electron transfer (SET) in thses processes. The possibility of SET from the hydroxide ion (HI) to the sulfophthalide molecule is determined by the ratio between the ionization potential (IP) of the HI and electron affinity (EA) of the sulfophthalide. According to B3LYP/6-311+G(d,p) calculations for DPSP, EA _ver = 0.06 eV and EA _ad = 0.58 eV, whereas EA _eff = 2.13 eV (with consideration of the C-O bond rupture in the sulfophthalide cycle). Such a value of the electron affinity cannot ensure SET from the HI, the ionization potential of which in DMSO reaches ∼5.25 eV. The EA of the carbocation formed from DPSP is 6.44 eV as calculated in the same approximation. A mode of SET from the HI to the carbocation intermediate formed during DPSP heterolysis in DMSO is proposed. Two possible modifications of the electron donor are considered. The possibility of occurrence of SET from the dimsyl ion and HI-DMSO complex is evaluated using the G3B3 method. The ionization potential of the dimsyl ion in DMSO is almost 1 eV lower than the IP of the HI, which makes the former a preferential donor in comparison with the HI. The ionization potential of the weak HI-DMSO complex even exceeds the IP of the HI; i.e., complexation does not improve the electron-donor properties of the hydroxide ion.     

Modification of X-ray excited photoelectron and C KVV Auger spectra during radiative carbonization of poly(vinylidene fluoride)

Modifications of the photoelectron and C KVV Auger spectra during the long-term surface degradation of partially crystalline PVDF under simultaneous soft X-ray and electron followed by ion irradiation are reported. Deep radiative carbonization brings about the formation of carbynoid structures (chain-like carbon) in the surface, while the number of interchain cross-links is insignificant. As a result, the shape of the electron emission spectra of carbon in the carbonized sample essentially differs from that of graphite and PVDF. The ion bombardment of the carbonized sample destroys one-dimensional structure due to the formation of cross-links. Thus, carbon atoms transit into sp²-hybrid state and, therefore, the photoelectron and Auger spectra show features characteristic for microcrystalline graphite.     

On the radiative pion decay

A reanalysis of the radiative pion decay together with the calculation of the radiative corrections within chiral perturbation theory (CHPT) is performed. The amplitude of this decay contains an inner Bremsstrahlung contribution and a structure-dependent part, which are both accessible in experiments. In order to obtain a reliable estimate of the hadronic contributions we combine the CHPT result with a large-N_c expansion and experimental data on other decays, which makes it possible to determine the occurring coupling constants. PACS  13.20.Cz; 12.39.Fe     

On the radiative decays of pions

A critical analysis of the theory of the radiative decays π → ?νγ (?: electron or muon) is given. Earlier results are corrected through a consistent application of gauge invariance and low-energy theorems. Predictions of specific models for the axial-vector form factor are discussed. The paper concludes with remarks on the relate$\text{π →}\text{e}\text{ν}\text{e}\text{e}$.     

On the possibility of improper antiferromagnetism

It has been shown that a magnetic phase transition of the second order with the tensor order parameter can be accompanied by the appearance of the magnetization of sublattices due to exchange effects.     

On the possibility of sorting ortho and para water molecules during diffusion in nanopores

The possibility of spatial sorting of ortho and para water molecules at filtering water vapor in a nanoporous medium is justified. Three factors are indicated, which in combination can cause sorting: Knudsen character of motion of molecules in nanopores, inhomogeneous surface electric fields in pores, and water molecule sorting over rotational states in an inhomogeneous electric field, recently implemented in experiments with molecular beams.     

On the one-dimensional Coulomb problem

We analyse the one-dimensional Coulomb problem (1DCP) pointing out some mistaken beliefs on it. We show that no eigenstates of even or odd parity can represent states of the system. The 1DCP exhibits a sort of spontaneous breaking of parity. We also show that a superselection rule operates in the system. Such rule explains some of its peculiarities. We build the superpotential associated to the 1DCP.     

On the irreversible thermophysics of radiative processes

The local aspect of the thermalization of thermal radiation due to the interaction of thermal radiation with matter is explored. It is shown that for absorption and emission interactions some well-known phenomenological statements of irreversible thermophysics are indeed relevant. For scattering interactions the entirely different picture that emerges is also briefly discussed. The local analysis is based on the concepts of temperature and entropy of nonequilibrium thermal radiation fields, as originally introduced by Planck, and shows that these concepts are susceptible of a very natural thermodynamic interpretation.     

On the quantisation of one-dimensional bags

We discuss the quantisation of one-dimensional MIT bags by expanding the fields as a sum of classical modes and truncating the series after the first term. We obtain the lowest states of a bag in a world containing two scalar quark fields. Problems associated with the zero-point oscillations of the field are discussed.     

On the possibility of local hidden-variable theories

It is shown that Bell inequality on local hidden-variable (LHV) theories does not apply to all of them. Therefore, there is no experimental evidence against LHV theories.     

On the possibility of fluctuation-driven first-order transitions

Available experimental material on phase-transitions of cubic compounds to type I- or type II-antiferromagnetism is briefly reviewed. Particular emphasis is paid to the question of whether they exhibit fluctuation-driven discontinuous transitions as claimed by a series of renormalization-group (RG) investigations for order-parameters withn4 degrees of freedom. It turns out that only less than one quarter of the known transitions are classified to be of first order. For most of these, the dominant spin-lattice couplings, i.e. exchangestriction of 3d-ions and magnetostriction and quadrupole-quadrupole interaction forf-ions, are known from independent experiments. Taking this into account, the discontinuous behaviour of the order parameter and related thermodynamic properties were fully explained neglecting critical fluctuations, i.e. by mean-field or randomphase approximations. In the remaining systems, the discontinuity predicted by the RG is not observed, for which several reasons may be responsible: (i) extremely small jumps of the order parameter that are below the limits of experimental resolution or are smeared out by imperfections, (ii) compounds with small spin-lattice interactions may exhibit an-K instead of a single-K structure postulated by the RG-work, and (iii) failure of the RG-criteria established at four dimensions for first-order transitions of readd=3 magnets.     

On the possibility of detecting superheavy quasimolecules

The formation of superheavy electronic quasimolecules leads to measurable deviations from the Rutherford cross section in heavy ion collisions. For the system ²³⁸₉₂U-²³⁵₉₂U with E_c.m. = 800 MeV we find an average correction of 1.5% for the scattering cross section in forward directions. Additional background contributions like electronic shielding of the nucleus, vacuum polarization, nuclear Coulomb excitation and static deformations of the nuclei are taken into account.