A new computer program has been developed which allows us to use the R-matrix method to study electron scattering by polyatomic molecules. Our first application is to scattering by in its linear, equilibrium geometry for energies up to 10 eV. We confirm the earlier assignment of symmetry to the resonance near 2 eV but we are unable to locate any resonance having symmetry in this energy range. We present integral and differential cross sections which are generally in excellent agreement with experiment.

ln this paper, we present a discussion of the role that angular momentum plays in the interaction of an intense laser field with a single-electron atom. To do this, we have made a detailed analysis of how diferent partial waves, i.e. , di8'erent angular-momentum states, participate in producing the photoelectron energy, angular distributions, and harmonic generation spectra. We show that the two regimestunneling and multiphoton excitationcorrespond to quite distinct evolution patterns across the partial wave decomposition. The natures of these patterns are particularly significant in the harmonic generation spectra and emphasize how harmonic generation is mainly produced in transitions back to the initial state. We also find that at high intensities, the photoelectron energy spectrum is composed of two di8'erent but well defined sets of above-threshold ionization peaks.These two sets are separated by a structureless region and the second set deviates substantially from the initial exponential decrease of the peak intensities versus energy. Similar features have been very recently reported experimentally.PACS number(s): 32.80.Rm, 42.50.Hz

The R-matrix method has been used to study low-energy electron impact on the X 2 ground state of the OH molecule. We find that the X 1 + ground state and first 3 excited state of the OH − anion are bound at all geometries studied, although in the latter case the binding is very weak. The first 1 state of the negative ion is also weakly bound for bond lengths greater than 2.5 a 0 . In the low-energy range studied, the vibrationally inelastic cross sections are dominated by the overall symmetries. The vibrational levels of the anion states appear as sharp resonances in the scattering. No structure was observed in the 1 + symmetry, but this can be attributed to the the long lifetimes and unfavourable Franck-Condon factors of the states involved. We also present both elastic and vibrationally inelastic differential cross sections for selected scattering energies.

We present a detailed study of a salt-free cationic/anionic (catanionic) surfactant system where a strongly alkaline cationic surfactant (tetradecyltrimethylammonium hydroxide, TTAOH) was mixed with a single-chain fluorocarbon acid (nonadecafluorodecanoic acid, NFDA) and a hyperbranched hydrocarbon acid [di-(2-ethylhexyl)phosphoric acid, DEHPA] in water. Typically the concentration of TTAOH is fixed while the total concentration and mixing molar ratio of NFDA and DEHPA is varied. In the absence of DEHPA and at a TTAOH concentration of 80 mmol·L(-1), an isotropic L(1) phase, an L(1)/L(α) two-phase region, and a single L(α) phase were observed successively with increasing mixing molar ratio of NFDA to TTAOH (n(NFDA)/n(TTAOH)). In the NFDA-rich region (n(NFDA)/n(TTAOH) > 1), a small amount of excess NFDA can be solubilized into the L(α) phase while a large excess of NFDA eventually leads to phase separation. When NFDA is replaced gradually by DEHPA, the mixed system of TTAOH/NFDA/DEHPA/H(2)O follows the same phase sequence as that of the TTAOH/NFDA/H(2)O system and the phase boundaries remain almost unchanged. However, the viscoelasticity of the samples in the single L(α) phase region becomes higher at the same total surfactant concentration as characterized by rheological measurements. Cryo-transmission electron microscopic (cryo-TEM) observations revealed a microstructural evolution from unilamellar vesicles to multilamellar ones and finally to gaint onions. The size of the vesicle and number of lamella can be controlled by adjusting the molar ratio of NFDA to DEHPA. The dynamic properties of the vesicular solutions have also been investigated. It is found that the yield stress and the storage modulus are time-dependent after a static mixing process between the two different types of vesicle solutions, indicating the occurrence of a dynamic fusion between the two types of vesicles. The microenvironmental changes induced by aggregate transitions were probed by (19)F NMR as well as (31)P NMR measurements. Upon replacement of NFDA by DEHPA, the signal from the (19)F atoms adjacent to the hydrophilic headgroup disappears and that from the (19)F atoms on the main chain becomes sharper. This could be interpreted as an increase of microfluidity in the mixed vesicle bilayers at higher content of DEHPA, whose alkyl chains are expected to have a lower chain melting point. Our results provide basic knowledge on vesicle formation and their structural evolution in salt-free catanionic surfactant systems containing mixed ion pairs, which may contribute to a deeper understanding of the rules governing the formation and properties of surfactant self-assembly.

Within the frame of the CLaRyS collaboration, we discuss the assets of using a reduced-intensity in vivo treatment control phase during one or a few beam spots at the beginning of a particle therapy session. By doing so we can improve considerably the conditions for secondary radiation detection and particle radiography. This also makes Time-of-Flight (ToF) resolutions of 100 ps rms feasible for both the transmitted particles and secondary radiations, by means of a single-projectile counting mode using a beam-tagging monitor with time and position registration. This opens up new perspectives for prompt-gamma timing and Compton imaging for range verification. ToF-based proton computed tomography (CT) and ToF-assisted secondary proton vertex imaging in carbon therapy are also discussed, although for the latter, no evidence of any benefit at small observation angles is anticipated. The reduction of the beam intensity during one or a few spots on the various accelerators for particle therapy should not significantly reduce the patient workflow.