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V V Petrunin

Publications and source records attributed to V V Petrunin.

9 recordsLinked to original sources
PubMed2006

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.

Journal Article↗
PubMed2005

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.

Journal Article↗
PubMed2003

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.

Astronomical Phenomena↗
PubMed2003

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.

Journal Article↗
PubMed2001

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.

Journal Article↗
PubMed2000

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.

Journal Article↗
PubMed1999

[Triangular anastomoses in surgery of the stomach].

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.

Anastomosis, Roux-en-Y↗