Yu. S. Doronin

Size effect in the desorption of excited atoms and molecules from clusters of inert elements under electron bombardment

New channels of desorption of excited atoms and molecules from clusters of argon, krypton, and xenon under electron bombardment are found by the method of vacuum ultraviolet emission spectroscopy. The maximum yield of particles is registered in the interval of average sizes of 50–100 atoms/cluster. The regularities and features of the desorption of excited particles are revealed, making it possible to establish a new desorption mechanism called nonradiative excimeric dissociation. It is shown that the main stages of this mechanism are: the formation of molecular centers of the nature of highly excited diatomic excimer molecules in clusters in the process of self-trapping of high-energy p excitons (n=1); the nonradiative dissociation of these molecules to excited atoms and atoms in the ground state with large kinetic energies. It is established that the appearance of new channels of desorption of excited atoms and molecules from clusters under bombardment by electrons is due to features of the physical pro...

Phase separation into pure components in mixed Ar-Xe clusters

Phase equilibrium in binary clusters of heavy inert gases has been studied using a combination of electron diffraction and optical methods. Mixed Ar-Xe clusters exhibit the phenomenon of phase separation into pure components with the formation of a sharp interface between the xenon core and argon shell, which is not observed in massive samples of this system.

Luminescence evidence for bulk and surface excitons in free xenon clusters

The cathodoluminescence spectra of free xenon clusters produced by condensation of xenon-argon gas mixtures in supersonic jets expanding into vacuum were studied. By varying the initial experimental parameters, including the xenon concentration, we could obtain clusters with a xenon core (300--3500 atoms) covered by an argon outer shell as well as shell-free xenon clusters (

Spectroscopy of mixed Ar-Xe clusters: Formation of a xenon core

\ensuremath{\approx}1500

Observation of exciton luminescence from icosahedral xenon-argon clusters

atoms). The cluster size and temperature (

Heterogeneous cluster formation in a supersonic argon-krypton jet according to cathodoluminescence data in the vacuum ultraviolet

\ensuremath{\approx}40\phantom{\rule{0.3em}{0ex}}\mathrm{K}

Influence of the size effect in the exciton energy spectrum on exciton relaxation in rare gas clusters

for both cases) were measured electronographically. Luminescence bands evidencing the existence of bulk and surface excitons were detected for shell-free xenon clusters. The emission from bulk excitons in small clusters is supposed to be due to processes of their multiple elastic reflections from the xenon-vacuum interface. The presence of an argon shell causes extinction of the excitonic bands. In addition, some bands were found which have no analogs for bulk xenon cryosamples.

Direct observation of free excitons in the luminescence spectra of xenon clusters

The spectra of vacuum ultraviolet luminescence of heteroatomic Ar-Xe clusters condensed in supersonic jets of a mixture of these gases at a xenon impurity concentrations of 0.001–2% are measured. A new group of molecular luminescence bands of argon-xenon centers is recorded, which allows a highly sensitive detection of xenon in the argon matrix of a cluster. The phenomenon of phase separation into pure components with formation of a sharp interface between the xenon core and argon shell of the cluster is found.

Spectroscopic observation of (N2)2dimers in free icosahedral N2and Ar-N2clusters

Exciton-impurity luminescence is observed for the first time in binary mixtures of solidified rare gases, in the xenon-argon system with argon as the impurity. An intense exciton-impurity emission band is observed in binary clusters having the structure of a multilayered icosahedron. The optical transition occurs from an energy level lying very close to the lowest bulk exciton level in bulk xenon samples. The results demonstrate the potential for probing exciton levels in disordered condensed rare gas media.

Analysis of luminescence spectra of substrate-free icosahedral and crystalline clusters of argon

Processes of cluster formation in a supersonic argon-krypton jet at low concentrations of the krypton impurity (down to 1×10−3%) are investigated by a luminescence method. VUV diagnostics of the picture of heterogeneous nucleation, including its earliest stages, is employed for the first time. Attention is focused mainly on the behavior of the emission bands belonging to the neutral excimers Ar2* and Kr2* and the charged homoatomic complexes (Ar4+)* and (Kr4+)* and the heteroatomic exciplexes (Ar∕Kr)*. In the first stage of heterogeneous nucleation the nuclei can be krypton atoms (dimers). Beginning at krypton concentrations in the gas mixture of 0.02% and higher a multiatomic krypton core is formed in the cluster. When such clusters are ionized the ion is located in the krypton core, and its electric field has a substantial influence on the parameters of the emission band of an Ar∕Kr molecule found at the argon/krypton boundary. The results of this study demonstrate the high efficiency of VUV spectroscop...