Reactive and nonreactive modes of electronic excitation and molecular dissociation in hyperthermal collisions of alkali atoms with alkali halides

1975 ◽  
Vol 63 (2) ◽  
pp. 1030-1032 ◽  
Author(s):  
S. K. Neoh ◽  
D. R. Herschbach
Keyword(s):  
Electronic Excitation ◽  
Alkali Halides ◽  
Molecular Dissociation ◽  
Alkali Atoms

Atomic and molecular emission following fracture of alkali halides: A dislocation driven process

1991 ◽  
Vol 6 (1) ◽  
pp. 112-125 ◽  
Author(s):  
J.T. Dickinson ◽  
L.C. Jensen ◽  
S.C. Langford ◽  
J.P. Hirth
Keyword(s):  
Heat Treatment ◽  
Molecular Species ◽  
Neutral Particle ◽  
Alkali Halides ◽  
Time Intervals ◽  
Neutral Species ◽  
Free Surfaces ◽  
Alkali Atoms ◽  
Fracture Event ◽  
Long Time

During and following fracture of a number of materials, the emission of photons, electrons, ± ions, and neutral species are observed; these emissions are collectively known as fracto-emission. In this work, we present measurements of the neutral particle emission following fracture of two single crystal fcc alkali halides: NaCl and LiF. We observe no measurable emission attributable to release during the fracture event itself. However, after relatively long time intervals of ∼0.5–250 ms, we observe rapid bursts of alkali atoms, as well as molecular species which include NaCl and (LiF)n where n = 1,2,3. Bursts of alkali containing species also occur during loading prior to fracture and for unloaded specimens during heat treatment. We argue that these bursts are due to energetic emergence (“popout”) of dislocations at free surfaces.

An Effect of Hydrostatic Compression on Defects in Energetic Materials: AB Initio Modeling Maija

1998 ◽  
Vol 538 ◽  
Author(s):  
M. Kuklja ◽  
A. Barry Kunz
Keyword(s):  
Band Gap ◽  
Edge Dislocation ◽  
Hot Spots ◽  
Energetic Materials ◽  
Electronic Excitation ◽  
First Principle ◽  
Molecular Dissociation ◽  
External Hydrostatic Pressure ◽  
Pressure Changes ◽  
Favorable Conditions

AbstractFirst-principle theoretical investigation of the basic defects such as a molecular vacancy, a vacancy dimer, an edge dislocation, and a micro-crack in organic explosive molecular crystals is presented. As an example we considered solid RDX (C3H6N6O6) which is well studied unstable solid. It was established that external hydrostatic pressure changes optical properties of defect-free RDX as well as of the crystal with defects narrowing the band gap. The lattice defects (especially dislocations) are identified with the so-called “hot spots.” The nature of local electronic states introduced in the band gap by the edge dislocation and formed mainly by molecular orbitals of N-NO2 group is analyzed. Favorable conditions for molecular dissociation due to electronic excitation are shown.

Theory of excitation transfer in collisions between alkali atoms. I. Identical partners

1969 ◽  
Vol 47 (12) ◽  
pp. 1237-1248 ◽  
Author(s):  
E. I. Dashevskaya ◽  
A. I. Voronin ◽  
E. E. Nikitin
Keyword(s):  
Excitation Energy ◽  
Excited States ◽  
Cross Section ◽  
Electronic Excitation ◽  
Electronic States ◽  
Excitation Transfer ◽  
Electronic Excitation Energy ◽  
Alkali Atoms ◽  
The Cross

A mechanism is derived for nonresonant transfer of electronic excitation energy, induced in the process M*(2P3/2) + M(2S1/2) → M*(2P1/2) + M(2S1/2), where M and M* are identical alkali atoms in the ground and first excited states, respectively. Various types of interactions, responsible for the nonadiabatic combination of electronic states of the quasi molecule M2*, were considered, and their respective contributions to the cross section for excitation transfer were determined.

Photon-stimulated desorption of excited alkali atoms from alkali halides following core-level excitation

1991 ◽  
Vol 243 (1-3) ◽  
pp. A90
Author(s):  
P.H. Bunton ◽  
R.F. Haglund ◽  
D. Liu ◽  
N.H. Tolk
Keyword(s):  
Alkali Halides ◽  
Core Level ◽  
Alkali Atoms
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