Effective Hamiltonian for fluid interfaces

Based on a microscopic theory of inhomogeneous fluids we derive a non-Gaussian and nonlocal effetive Hamiltonian of a liquid-vapor interface. A partial resummation of a gradient expansion yields terms proportional to the area as well as to the Gaussian and the square of the mean curvature of the interface. For van der Waals fluids the gradient expansion breaks down and leads to a singularity in the momentum dependent surface tension. The nonlocal Hamiltonian and various approximations thereof are compared quantitatively.     

Generation of radiation on yellow and infrared lines in sodium vapour excited to the 4P level

Generation of the radiation pulses on resonant (589 nm) as well as infrared (2210 nm and 1140 nm) lines was observed in sodium vapour excited by laser light tuned to the 3S–4P transition.     

Linewidth studies on the Kr+ 469.4 nm and 473.9 nm lines excited in a helium-krypton hollow cathode discharge

Collisional and Doppler linewidths (v _C and v _D ) of the 469.4 nm and 473.9 nm Kr ion lines were measured in a He-Kr hollow cathode discharge using Fabry-Perot technique. A linear dependence of v _C on He pressure was found for both lines. Significant differences were found between the temperature values deduced from the v _D -s of the two lines, and an unexpected temperature dependence of the broadening parameter for the Kr⁺ 469 nm line was also observed. The temperature difference between the two lines is explained by excitation of the upper level of the 469 nm line by second kind collisions between metastable He atoms and ground-state Kr ions, while the temperature dependence of the broadening parameter of the Kr⁺ 469 nm line is suggested to be due to the inverse process.     

Laser-induced electron emission from an Au surface irradiated by single picosecond pulses at λ=2.94 μm. The intermediate region between multiphoton and tunneling effects

The photoinduced electron emission from the surface of a solid gold target irradiated by single picosecond pulses of an erbium laser is investigated. The applied laser intensity (5–120 GW/cm²) corresponds to the intermediate interaction region between the pure multiphoton and tunnel effects, where the decisive Keldysh-parameter, , is in the range 1<<12=n ₀. In the light intensity region which is free of surface heating (I _L<80 GW/cm²), the slope of the measured logarithmic intensity dependence of the photocurrent decreases from the n ₀=12 perturbative value down to n 5. Therefore the experiment shows that the Keldysh-type theories, which have recently been proved to describe correctly the ionization of atoms, are also valid to a certain extent in the case of the photoeffect in metals.