Sub-monolayer Au9 cluster formation via pulsed nozzle cluster deposition

Submonolayer coverages of chemically synthesised triphenylphosphine-protected Au9 clusters on mica and TiO2 substrates were achieved through the development of a Pulsed Nozzle Cluster Deposition (PNCD) technique under high vacuum conditions.

Изотопно-селективное управление кластеризацией молекул SF-=SUB=-6-=/SUB=- и диссоциация ван-дер-ваальсовых кластеров (SF-=SUB=-6-=/SUB=-)-=SUB=-m-=/SUB=-Ar-=SUB=-n-=/SUB=- ИК лазерным излучением

We present the results of an investigation into the interaction of SF_6 molecules and clusters in a molecular beam with resonant IR laser radiation at different stages of the beam evolution along the axis of its propagation. The beam has been formed as a result of gas-dynamic expansion of a mixture of SF_6 with argon carrier gas during expansion from a pulsed nozzle. The experimental setup and the investigation method are described. It has been shown that selective vibrational excitation of SF_6 molecules with a specific sulfur isotope by a CO_2 laser near the nozzle edge causes suppression of the clustering process of these isotopic molecules. Selective IR excitation of clusters under the conditions of the formed cluster beam leads to isotopically selective dissociation of clusters. Depending on the experimental conditions including different distances of the irradiation zone of particles from the nozzle edge, the results of measuring the efficiency and selectivity of molecular clustering suppression and cluster dissociation processes are presented. It has been shown that both of these processes make it possible to achieve high selectivity values for the ^32S and ^34S sulfur isotopes. In the case in which the clustering of SF_6 molecules was selectively suppressed, selectivity values α ≥ 25–30 have been obtained. Upon selective dissociation of (SF_6)_2 dimers under similar expansion conditions of the gas mixture, selectivity values α ≥ 20–25 for ^32SF_6^32SF_6 dimers with respect to ^34SF_6^32SF_6 dimers have been obtained. Particular attention has been paid to measurements at a high dilution of SF_6 in argon under conditions of predominant formation of (SF_6)_ m Ar_ n mixed clusters. The potential of using studied processes as a basis for the technology of the laser isotope separation are discussed.

Observation of the simplest Criegee intermediate CH2OO in the gas-phase ozonolysis of ethylene

Ozonolysis is one of the dominant oxidation pathways for tropospheric alkenes. Although numerous studies have confirmed a 1,3-cycloaddition mechanism that generates a Criegee intermediate (CI) with form R1R2COO, no small CIs have ever been directly observed in the ozonolysis of alkenes because of their high reactivity. We present the first experimental detection of CH2OO in the gas-phase ozonolysis of ethylene, using Fourier transform microwave spectroscopy and a modified pulsed nozzle, which combines high reactant concentrations with rapid sampling and sensitive detection. Nine other product species of the O3+ C2H4reaction were also detected, including formaldehyde, formic acid, dioxirane, and ethylene ozonide. The presence of all these species can be attributed to the unimolecular and bimolecular reactions of CH2OO, and their abundances are in qualitative agreement with published mechanisms and rate constants.

Study on Internal Flow Field of Series Pulsed Nozzle

This paper describes experimental study and numerical simulation of series pulsed nozzle. The simulation of internal flow field in nozzle with different cavity length was carried out by using CFD. The influence of chamber length on the velocity distribution and the axial velocity was analyzed. The simulation results indicate that there is a optimum rang of cavity length producing the maximum outlet velocity. The dynamic pressure of pulsed jet was also studied by using SD150 test system. The effect law of chamber length on the impact pressure of pulsed jet was analyzed. The experimental results show that the peak of hitting power reaches the maximum within a certain range of cavity length. Simulation results are in agreement with Experimental results.