Coulomb-Explosion

Coulomb explosion is a method in which, for example, by a focused laser beam, a solid material goes into the plasma state.

Description

The physical mechanism is that the electrons are excited by the strong electromagnetic field of the beam and its excitation energy is coupled to the atomic movement. The atomic motion can dissolve the bond that holds together solid bodies. The outer valence electrons, which are responsible for the chemical bonding, can be easily separated from the atom and leave this positively charged back. Atoms whose bonds are broken in this way, repel each other, and the material explodes into a small cloud of high-energy ions that have higher rates than if they would evaporate by heat.

In biology, the principle of Coulomb explosion may be effective in the stinging cells.

Applications

The Coulomb explosion is one of the mechanisms by which metal processing with lasers (laser cutting, laser drilling, laser ablation, laser marking, etc.) is possible.

Coulomb explosions in industrial material processing caused by short laser pulses ( in the picosecond or femtosecond range high ). The enormously high beam intensities required ( 10 to 400 TW/cm2 ) can be practically handled only for very short periods of time.

Coulomb explosion is a "cold" process alternative to the prevailing thermal ablation due to the local heating, melting and evaporation of the molecules and atoms by less intensive radiation (see, for example, laser marking ).

Pulses in the nanosecond range are short enough to locate the thermal ablation: the power supply ( of the pulse ) is finished before the heat is transferred. However, thermally ablated materials close pores that are important for catalytic converters or for battery operation, and recrystallizing the substrate or even burn, thus changing the physical and chemical properties of the machined body. In contrast, even remain unsealed lightweight foams for processing by Coulomb explosions.

Coulomb explosions with each material are used to drill holes, remove surface layers and to give surfaces a texture or microstructure; For example, to control the amount of the adhesive on the roll printing ink in printing machines.