Vacuum scanning capillary photoemission microscopy.

We demonstrate the use of a conical capillary in a scanning probe microscopy for surface analysis. The probe can measure photoemission from a substrate by transmitting photoelectrons along the capillary as a function of probe position. The technique is demonstrated on a model substrate consisting of a gold reflecting layer on a compact disc which has been illuminated by an unfocused laser beam with a wavelength 400nm, from a femtosecond laser with a beam size of 4mm. A quartz capillary with a 2-µm aperture has been used in the experiments. The period of gold microstructure, shown to be 1.6µ, was measured by the conical probe operating in shear force mode. In shear force regime, the dielectric capillary has been used as a "classical" SPM tip, which provided images reflecting the surface topology. In a photoelectron regime photoelectrons passed through hollow tip and entered a detector. The spatial distribution of the recorded photoelectrons consisted of periodic mountain-valley strips, resembling the surface profile of the sample. Submicron spatial resolution has been achieved. This approach paves the way to study pulsed photodesorption of large organic molecular ions with high spatial and element resolution using the combination of a hollow-tip scanner with time-of-flight technique.

Translational energy and state resolved observations of D and D2 thermally desorbing from D clusters chemisorbed on graphite.

Direct D atom desorption, as well as associative desorption of D(2) molecules are observed in thermal desorption from D atoms chemisorbed on a C(0001) surface by combining laser induced T-jumps with resonance enhanced multiphoton ionization detection. Bleaching curves suggest that different classes of chemisorbed D atom clusters are present on the initial surface. The energy resolved atomic desorption flux, obtained via time of flight techniques, compares favorably (via detailed balance) with theoretical calculations of atomic sticking. Density functional theory calculations of chemical processes (atomic desorption, atomic diffusion/cluster annealing, and associative desorption) on an extensive set of four atom H(D) clusters chemisorbed on C(0001) provide a good interpretation of the experiments. State and energy resolved D(2) desorption fluxes are compared with previous state averaged results. In combination with density functional theory calculations these measurements reveal a substantial energy loss (>1 eV) to the surface in the associative desorption.

High translational energy release in H2 (D2) associative desorption from H (D) chemisorbed on C(0001).

Highly energetic translational energy distributions are reported for hydrogen and deuterium molecules desorbing associatively from the atomic chemisorption states on highly oriented pyrolytic graphite (HOPG). Laser assisted associative desorption is used to measure the time of flight of molecules desorbing from a hydrogen (deuterium) saturated HOPG surface produced by atomic exposure from a thermal atom source at around 2100 K. The translational energy distributions normal to the surface are very broad, from approximately 0.5 to approximately 3 eV, with a peak at approximately 1.3 eV. The highest translational energy measured is close to the theoretically predicted barrier height. The angular distribution of the desorbing molecules is sharply peaked along the surface normal and is consistent with thermal broadening contributing to energy release parallel to the surface. All results are in qualitative agreement with recent density functional theory calculations suggesting a lowest energy para-type dimer recombination path.

Influence of surface morphology on D2 desorption kinetics from amorphous solid water.

The influence of surface morphology/porosity on the desorption kinetics of weakly bound species was investigated by depositing D2 on amorphous solid water (ASW) films grown by low temperature vapor deposition under various conditions and with differing thermal histories. A broad distribution of binding energies of the D2 monolayer on nonporous and porous ASW was measured experimentally and correlated by theoretical calculations to differences in the degree of coordination of the adsorbed H2 (D2) to H2O molecules in the ASW depending on the nature of the adsorption site, i.e., surface valleys vs surface peaks in a nanoscale rough film surface. For porous films, the effect of porosity on the desorption kinetics was observed to be a reduction in the desorption rate with film thickness and a change in peak shape. This can be partly explained by fast diffusion into the ASW pore structure via a simple one-dimensional diffusion model and by a change in binding energy statistics with increasing total effective surface area. Furthermore, the D2 desorption kinetics on thermally annealed ASW films were investigated. The main effect was seen to be a reduction in porosity and in the number of highly coordinated binding sites with anneal temperature due to ASW restructuring and pore collapse. These results contribute to the understanding of desorption from porous materials and to the development of correct models for desorption from and catalytic processes on dust grain surfaces in the interstellar medium.

Importance of surface morphology in interstellar H2 formation.

Detailed laboratory experiments on the formation of HD from atom recombination on amorphous solid water films show that this process is extremely efficient in a temperature range of 8 to 20 kelvin, temperatures relevant for H2 formation on dust grain surfaces in the interstellar medium (ISM). The fate of the 4.5 electron volt recombination energy is highly dependent on film morphology. These results suggest that grain morphology, rather than the detailed chemical nature of the grain surface, is most important in determining the energy content of the H2 as it is released from the grain into the ISM.

Photodetachment of He- in the vicinity of the two-electron escape threshold.

Recording the yield of He(1snl(3)L) Rydberg states for n=11-14, we measure the photodetachment cross sections of metastable He-(1s2s2p(4)P(o)) ions in the vicinity of the two-electron escape threshold. We observe a large number of double Rydberg He- quartet state resonances and report energies and widths of intrashell states in the n=13-15 manifolds. Sharp thresholds are measured at He((3)P(o)) and He((3)D(e)) Rydberg states with preference for population of the former, whereas the He((3)S(e)) states are not populated, in agreement with qualitative theoretical arguments.

Observation of a 1/t decay law for hot clusters and molecules in a storage ring.

The exponential law is valid both for decay from a single quantum state into a continuum and for an ensemble maintained in thermal equilibrium. For statistical decay of an ensemble of isolated systems with a broad energy distribution, the exponential decay is replaced by a 1/t distribution. We present confirmation of this decay law by experiments with cluster anions in a small electrostatic storage ring. Deviations from the 1/t law for such an ensemble give important information on the dynamics of the systems. As examples, we present measurements revealing strong radiative cooling of anions of both metal clusters and fullerenes.

High-resolution vacuum-ultraviolet spectroscopy of an electron-cooled D- beam.

The shape parameters for the lowest-lying (1)P(o) resonance, (2)¿0¿-3, of D- have been measured using high-resolution vacuum-ultraviolet spectroscopy. The experiment was performed at the storage ring ASTRID, and the resonance was resolved by applying electron cooling to reduce the velocity spread of the ion beam. The resonance has a width of 37(3) microeV while the asymmetry parameter q of the Fano profile is -16(3). These values present the first critical test of a large number of theoretical calculations.

[Triangular anastomoses in surgery of the stomach]. / Trianguliarnye anastomozy v khirurgii zheludka.

The mode of triangulation in the anastomoses of the stomach and the duodenum (thrice-repeated usage of linear suturing apparatuses in shaping anastomoses) is a perspective way for improvement of the results of surgical treatment of these organs. The results of 216 cases have shown that the use of the triangular anastomoses in gastric surgery allows a decrease in the rate of complications because of anastomosis failure in early postop period more than 3.5 times. The healing of such anastomoses proceeds by primary intention and in short terms and is accompanied by minimal inflammatory reaction. The course of restoration of the motor and evacuation function of the stomach after creation of such anastomoses is characterized by early, partial and timely evacuation. In remote postoperative period mechanical everted anastomoses, made up by linear suturing apparatuses, provide absence of the tendency for cicatricial strictures and stipulation of motor and evacuation functional characteristics of the stomach. The authors believe that beneficial impact of this method on gastric function allows to recommend it for wider use in surgery of the stomach.

Laser detection of the rare isotope (3)He at concentrations as low as 10(-9).

The method of collinear laser photoionization of atoms in a modulated fast beam is used to detect the rare isotope (3)He, with high-repetition-rate lasers being applied to improve the detection sensitivity. The method has made it possible to detect (3)He at relative abundances as low as 10(-9).