[en] The titanium surfaces immersed in 0.5 mol.dm^-3 H₂SO₄ and anodized in the voltage region from 0 to 100 V have been studied by in situ ellipsometric measurements. The thickness, inhomogeneity, and porosity of the formed films rise with increasing applied voltage. A computational method is presented for obtaining both the refractive indices and thickness of an unknown film on a reflecting substrate of known optical constants. The complex index of refraction and thickness of generated films were calculated comparing the theoretical computed curve with experimental loci Δ and Ψ obtained from in situ ellipsometric measurements. (orig.)

[en] The 7d_5/2nl double-Rydberg states of barium have been studied for n=11 to 14 and l=7 to n-1 using the Isolated Core Excitation technique along with a Stark switching method to populate the high l states. The resulting spectra show resolved structures due to the correlation between the two excited electrons, identified by the (jl)K angular momentum coupling between them. The spectra are compared to energy positions and linewidths calculated using a perturbative approach, including the dipole and quadrupole interaction terms. The agreement between experiment and theory is very good for high l≥9, but less so for lower l. (orig.)

[en] We describe the optimum detection procedure to follow in order to measure by atomic interferometry the number of photons present in a cavity by using a Quantum nondemolition scheme. The method we discuss is the one recently introduced by Brune et al., in which the field intensity is detected by recording atomic interferences in a Ramsey type set up. A succession of two-level atoms interacts with the cavity field which is the analog of a birefringent retarding plate for the atomic wave function. The information is acquired in the form of binary digits (atoms detected in one level or the other). We discuss an optimal strategy which yields the value of the photon number with a number of atoms of the order of the base 2 logarithm of the field photon number dispersion. The procedure described here is the one we intend to use in an experiment in preparation. (orig.)

[en] We have measured and analyzed the hyperfine structure of a large number of optical transitions belonging to the IF B-X system. These transitions sample a large range of rovibrational levels (9≤v''≤18 in the X state, 0≤v'≤10 in the B state, with J≤125). The hyperfine constants deduced from the observed spectra present some interesting variations with the rovibrational levels. We analyze carefully the electric quadrupole coupling constant in the X state and show that its variation is a sensitive probe of the ionic character of the IF molecular bond. (orig.)

[en] Averaging states with the same principal quantum number in hydrogenic ions and assuming the free electrons to be Maxwellian, we present convenient fits to the coefficients of spontaneous emission, radiative recombination and, with not too small a charge, excitation and ionization by electron impact. For the last two processes, the data available on low levels are complemented by a detailed consideration of the asymptotic constants of Bethe-Born, so as to cover a wide range of levels and temperatures. (orig.)

[en] It is well known that an electric field that is applied normally to the free surface of a conducting fluid has a destabilizing effect. Here we study the linear growth of electro-capillary instabilities in the very general case where the viscosity of the fluid and its thickness are of any value. We derive the asymptotic behaviour in various regimes and give analytical dispersion equations in the case of thin or thick, inviscid or viscous films and compare with previous results. Then we present a diagram of the corresponding simplifications of the dispersion relation and as we derive them directly from the general equation, we are able to derive their conditions of validity explicitly. We also show the similarities and the differences with the case of a liquid falling from a solid flat plane (Rayleigh-Taylor instabilities) without electric field and with ferrofluid instabilities. (orig.)

[en] The behaviour of doubly excited circular atoms in weak parallel electric and magnetic fields has been studied. The Hamiltonian, including the e-e interaction between the two excited electrons, Stark and Zeeman effects, is diagonalized in a truncated basis. The Rydberg electron, initially in a circular state, experiences a mixing of its orbital and magnetic quantum numbers, due to the presence of the external fields and to the excitation of the inner electron. This mixing depends on the spatial symmetry of the excited core and on the amplitude of the electric field. It can be detected by the field-ionization method which provides a new way for studying non-autoionizing doubly excited states. (orig.)

[en] Small Angle Neutron Scattering experiments were carried out on liquid crystalline ''side-on fixed'' polyacrylates: we observe that the polymer backbone adopts a prolate conformation in the nematic phase. Such anisotropy of the global backbone is larger for smaller spacer lenght. In every case we measure at low temperatures a large chain extension as previously described in polysiloxanes. (orig.)

[en] Excitation cross-sections of PrI were measured at an electron energy 30 eV for 82 spectral lines. We have used the method of extended crossing beams with detection of the optical signal. For half of the total number the energy dependences were measured in the electron energy range of 0..200 eV. The largest measured excitation cross-sections reach (5-8) x 10^-16 cm². A classification is suggested for 18 previously unclassified lines. (orig.)

[en] Recent experiments in high resolution laser-based spectroscopy extending into the VUV are described. Several motivations are discussed - in particular, the study of many-body effects and interchannel interactions. The phenomenon of autoionisation, especially when resonances overlap with each other and interact, is singled out, because it provides examples of several novel effects whose occurrence has only been established through high resolution experiments. The theory of these effects is outlined and several examples are given. The techniques involved in the data acquisition involve both thermionic diode detection and magneto-optical rotation as well as photoabsorption experiments. (orig.)