A Coulombic explosion is a condensed-matter physics process in which a molecule or crystal lattice is destroyed by the Coulombic repulsion between its constituent atoms. Coulombic explosions are a prominent technique in laser-based machining, and appear naturally in certain high-energy reactions.
A Coulombic explosion begins when an intense electric field (often from a laser) excites the valence electrons in a solid, ejecting them from the system and leaving behind positively charged ions. The chemical bonds holding the solid together are weakened by the loss of the electrons, enabling the Coulombic repulsion between the ions to overcome them. The result is an explosion of ions and electrons – a plasma.
The laser must be very intense to produce a Coulomb explosion. If it is too weak, the energy given to the electrons will be transferred to the ions via electron-phonon coupling. This will cause the entire material to heat up, melt, and thermally ablate away as a plasma. The end result is similar to Coulomb explosion, except that any fine structure in the material will be damaged by thermal melting. [1]
It may be shown that the Coulomb explosion occurs in the same parameter regime as the superradiant phase transition i.e. when the destabilizing interactions become overwhelming and dominate over the oscillatory phonon-solid binding motions.[ citation needed ]
A Coulomb explosion is a "cold" alternative to the dominant laser etching technique of thermal ablation, which depends on local heating, melting, and vaporization of molecules and atoms using less-intense beams. Pulse brevity down only to the nanosecond regime is sufficient to localize thermal ablation – before the heat is conducted far, the energy input (pulse) has ended. Nevertheless, thermally ablated materials may seal pores important in catalysis or battery operation, and recrystallize or even burn the substrate, thus changing the physical and chemical properties at the etch site. In contrast, even light foams remain unsealed after ablation by Coulomb explosion.
Coulomb explosions for industrial machining are made with ultra-short (picosecond or femtoseconds) laser pulses. The enormous beam intensities required (10–400 terawatt per square centimeter thresholds, depending on material) are only practical to generate, shape, and deliver for very brief instants of time.[ citation needed ] Coulomb explosion etching can be used in any material to bore holes, remove surface layers, and texture and microstructure surfaces; e.g., to control ink loading in printing presses. [2]
High speed camera imaging of alkali metals exploding in water has suggested the explosion is a coulomb explosion. [3] [4]
During a nuclear explosion based on the fission of uranium, 167 MeV is emitted in the form of a coulombic explosion between each prior nucleus of uranium, the repulsive electrostatic energy between the two fission daughter nuclei, translates into the kinetic energy of the fission products that results in both the primary driver of the blackbody radiation that rapidly generates the hot dense plasma/nuclear fireball formation and thus also both later blast and thermal effects. [5] [6]
Scientists at the University of Cologne Zoological Institute have suggested that coulomb explosion (specifically, the electrostatic repulsion of dissociated carboxyl groups of polyglutamic acid) may be part of the explosive action of nematocytes, the stinging cells in aquatic organisms of the phylum Cnidaria. [7]
Molecules are held together by a balance of charge between negative electrons and positive nuclei. When multiple electrons are expelled, either by laser irradiation or bombardment using highly charged ions, the remaining, mutually repulsive, nuclei fly apart in a Coulomb explosion. The structure of simple gas phase molecules can be determined by imaging which tracks the fragment trajectories. [8] [9] As of 2022 the method can work with up to 11-atom molecules. [10] [11]
A chemical bond is a lasting attraction between atoms or ions that enables the formation of molecules, crystals, and other structures. The bond may result from the electrostatic force between oppositely charged ions as in ionic bonds, or through the sharing of electrons as in covalent bonds. The strength of chemical bonds varies considerably; there are "strong bonds" or "primary bonds" such as covalent, ionic and metallic bonds, and "weak bonds" or "secondary bonds" such as dipole–dipole interactions, the London dispersion force, and hydrogen bonding.
The neutron is a subatomic particle, symbol
n
or
n0
, which has a neutral charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons behave similarly within the nucleus, and each has a mass of approximately one dalton, they are both referred to as nucleons. Their properties and interactions are described by nuclear physics. Protons and neutrons are not elementary particles; each is composed of three quarks.
Nuclear fusion is a reaction in which two or more atomic nuclei, usually deuterium and tritium, combine to form one or more different atomic nuclei and subatomic particles. The difference in mass between the reactants and products is manifested as either the release or absorption of energy. This difference in mass arises due to the difference in nuclear binding energy between the atomic nuclei before and after the reaction. Nuclear fusion is the process that powers active or main-sequence stars and other high-magnitude stars, where large amounts of energy are released.
Nuclear fission is a reaction in which the nucleus of an atom splits into two or more smaller nuclei. The fission process often produces gamma photons, and releases a very large amount of energy even by the energetic standards of radioactive decay.
Ionization is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule is called an ion. Ionization can result from the loss of an electron after collisions with subatomic particles, collisions with other atoms, molecules and ions, or through the interaction with electromagnetic radiation. Heterolytic bond cleavage and heterolytic substitution reactions can result in the formation of ion pairs. Ionization can occur through radioactive decay by the internal conversion process, in which an excited nucleus transfers its energy to one of the inner-shell electrons causing it to be ejected.
Ionizing radiation, including nuclear radiation, consists of subatomic particles or electromagnetic waves that have sufficient energy to ionize atoms or molecules by detaching electrons from them. Some particles can travel up to 99% of the speed of light, and the electromagnetic waves are on the high-energy portion of the electromagnetic spectrum.
Vaporization of an element or compound is a phase transition from the liquid phase to vapor. There are two types of vaporization: evaporation and boiling. Evaporation is a surface phenomenon, whereas boiling is a bulk phenomenon.
Muon-catalyzed fusion is a process allowing nuclear fusion to take place at temperatures significantly lower than the temperatures required for thermonuclear fusion, even at room temperature or lower. It is one of the few known ways of catalyzing nuclear fusion reactions.
Neutron radiation is a form of ionizing radiation that presents as free neutrons. Typical phenomena are nuclear fission or nuclear fusion causing the release of free neutrons, which then react with nuclei of other atoms to form new nuclides—which, in turn, may trigger further neutron radiation. Free neutrons are unstable, decaying into a proton, an electron, plus an electron antineutrino. Free neutrons have a mean lifetime of 887 seconds.
In nuclear physics and nuclear chemistry, a nuclear reaction is a process in which two nuclei, or a nucleus and an external subatomic particle, collide to produce one or more new nuclides. Thus, a nuclear reaction must cause a transformation of at least one nuclide to another. If a nucleus interacts with another nucleus or particle and they then separate without changing the nature of any nuclide, the process is simply referred to as a type of nuclear scattering, rather than a nuclear reaction.
Elastic scattering is a form of particle scattering in scattering theory, nuclear physics and particle physics. In this process, the kinetic energy of a particle is conserved in the center-of-mass frame, but its direction of propagation is modified meaning the two particles in the collision do not lose energy. Furthermore, while the particle's kinetic energy in the center-of-mass frame is constant, its energy in the lab frame is not. Generally, elastic scattering describes a process in which the total kinetic energy of the system is conserved. During elastic scattering of high-energy subatomic particles, linear energy transfer (LET) takes place until the incident particle's energy and speed has been reduced to the same as its surroundings, at which point the particle is "stopped".
Aneutronic fusion is any form of fusion power in which very little of the energy released is carried by neutrons. While the lowest-threshold nuclear fusion reactions release up to 80% of their energy in the form of neutrons, aneutronic reactions release energy in the form of charged particles, typically protons or alpha particles. Successful aneutronic fusion would greatly reduce problems associated with neutron radiation such as damaging ionizing radiation, neutron activation, reactor maintenance, and requirements for biological shielding, remote handling and safety.
Nuclear binding energy in experimental physics is the minimum energy that is required to disassemble the nucleus of an atom into its constituent protons and neutrons, known collectively as nucleons. The binding energy for stable nuclei is always a positive number, as the nucleus must gain energy for the nucleons to move apart from each other. Nucleons are attracted to each other by the strong nuclear force. In theoretical nuclear physics, the nuclear binding energy is considered a negative number. In this context it represents the energy of the nucleus relative to the energy of the constituent nucleons when they are infinitely far apart. Both the experimental and theoretical views are equivalent, with slightly different emphasis on what the binding energy means.
Electron scattering occurs when electrons are displaced from their original trajectory. This is due to the electrostatic forces within matter interaction or, if an external magnetic field is present, the electron may be deflected by the Lorentz force. This scattering typically happens with solids such as metals, semiconductors and insulators; and is a limiting factor in integrated circuits and transistors.
In nuclear and materials physics, stopping power is the retarding force acting on charged particles, typically alpha and beta particles, due to interaction with matter, resulting in loss of particle kinetic energy. Stopping power is also interpreted as the rate at which a material absorbs the kinetic energy of a charged particle. Its application is important in a wide range of thermodynamic areas such as radiation protection, ion implantation and nuclear medicine.
In atomic, molecular, and optical physics and quantum chemistry, the molecular Hamiltonian is the Hamiltonian operator representing the energy of the electrons and nuclei in a molecule. This operator and the associated Schrödinger equation play a central role in computational chemistry and physics for computing properties of molecules and aggregates of molecules, such as thermal conductivity, specific heat, electrical conductivity, optical, and magnetic properties, and reactivity.
Alpha particles, also called alpha rays or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. They are generally produced in the process of alpha decay, but may also be produced in other ways. Alpha particles are named after the first letter in the Greek alphabet, α. The symbol for the alpha particle is α or α2+. Because they are identical to helium nuclei, they are also sometimes written as He2+
or 4
2He2+
indicating a helium ion with a +2 charge. Once the ion gains electrons from its environment, the alpha particle becomes a normal helium atom 4
2He.
Bond softening is an effect of reducing the strength of a chemical bond by strong laser fields. To make this effect significant, the strength of the electric field in the laser light has to be comparable with the electric field the bonding electron "feels" from the nuclei of the molecule. Such fields are typically in the range of 1–10 V/Å, which corresponds to laser intensities 1013–1015 W/cm2. Nowadays, these intensities are routinely achievable from table-top Ti:Sapphire lasers.
Bond hardening is a process of creating a new chemical bond by strong laser fields—an effect opposite to bond softening. However, it is not opposite in the sense that the bond becomes stronger, but in the sense that the molecule enters a state that is diametrically opposite to the bond-softened state. Such states require laser pulses of high intensity, in the range of 1013–1015 W/cm2, and they disappear once the pulse is gone.
The helium trimer is a weakly bound molecule consisting of three helium atoms. Van der Waals forces link the atoms together. The combination of three atoms is much more stable than the two-atom helium dimer. The three-atom combination of helium-4 atoms is an Efimov state. Helium-3 is predicted to form a trimer, although ground state dimers containing helium-3 are completely unstable.
approximately 82% of the fission energy is released as kinetic energy of the two large fission fragments. These fragments, being massive and highly charged particles, interact readily with matter. They transfer their energy quickly to the surrounding weapon materials, which rapidly become heated
The various energies emitted per fission event pg 4. "167 MeV" is emitted by means of the repulsive electrostatic energy between the 2 daughter nuclei, which takes the form of the "kinetic energy" of the fission products, this kinetic energy results in both later blast and thermal effects. "5 MeV" is released in prompt or initial gamma radiation, "5 MeV" in prompt neutron radiation (99.36% of total), "7 MeV" in delayed neutron energy (0.64%) and "13 MeV" in beta decay and gamma decay(residual radiation)