Gas phase ion chemistry - AbsoluteAstronomy.com

Gas phase ion chemistry is a field of science encompassed within both chemistry

Chemistry

Chemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds....

and physics

Physics

Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...

. It is the science that studies ion

Ion

An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...

s and molecule

Molecule

A molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...

s in the gas phase, most often enabled by some form of mass spectrometry

Mass spectrometry

Mass spectrometry is an analytical technique that measures the mass-to-charge ratio of charged particles.It is used for determining masses of particles, for determining the elemental composition of a sample or molecule, and for elucidating the chemical structures of molecules, such as peptides and...

. By far the most important applications for this science is in studying the thermodynamics and kinetics

Chemical kinetics

Chemical kinetics, also known as reaction kinetics, is the study of rates of chemical processes. Chemical kinetics includes investigations of how different experimental conditions can influence the speed of a chemical reaction and yield information about the reaction's mechanism and transition...

of reactions. For example one application is in studying the thermodynamics

Thermodynamics

Thermodynamics is a physical science that studies the effects on material bodies, and on radiation in regions of space, of transfer of heat and of work done on or by the bodies or radiation...

of the solvation

Solvation

Solvation, also sometimes called dissolution, is the process of attraction and association of molecules of a solvent with molecules or ions of a solute...

of ions. Ions with small solvation

Solvation

Solvation, also sometimes called dissolution, is the process of attraction and association of molecules of a solvent with molecules or ions of a solute...

spheres of 1, 2, 3... solvent molecules can be studied in the gas phase and then extrapolated to bulk solution.

Transition state theory

Transition state theory is the theory of the rates of elementary reactions which assumes a special type of chemical equilibrium

Chemical equilibrium

In a chemical reaction, chemical equilibrium is the state in which the concentrations of the reactants and products have not yet changed with time. It occurs only in reversible reactions, and not in irreversible reactions. Usually, this state results when the forward reaction proceeds at the same...

(quasi-equilibrium) between reactants and activated complexes.

RRKM theory

RRKM theory is used to compute simple estimates of the unimolecular ion decomposition

Unimolecular ion decomposition

Unimolecular ion decomposition is the fragmentation of a gas phase ion in a reaction with a molecularity of one. Ions with sufficient internal energy may fragment in a mass spectrometer, which in some cases may degrade the mass spectrometer performance, but in other cases, such as tandem mass...

reaction rates from a few characteristics of the potential energy surface

Potential energy surface

A potential energy surface is generally used within the adiabatic or Born–Oppenheimer approximation in quantum mechanics and statistical mechanics to model chemical reactions and interactions in simple chemical and physical systems...

Gas phase ion formation

The process of converting an atom

Atom

The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...

or molecule

Molecule

A molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...

into an ion

Ion

by adding or removing charged particles such as electron

Electron

The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...

s or other ions can occur in the gas phase. These processes are an important component of gas phase ion chemistry.

Associative ionization

Associative ionization is a gas phase reaction in which two atom

Atom

s or molecule

Molecule

A molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...

s interact to form a single product ion

Ion

where species A with excess internal energy (indicated by the asterisk) interacts with B to form the ion AB⁺.

One or both of the interacting species may have excess internal energy

Internal energy

In thermodynamics, the internal energy is the total energy contained by a thermodynamic system. It is the energy needed to create the system, but excludes the energy to displace the system's surroundings, any energy associated with a move as a whole, or due to external force fields. Internal...

Charge-exchange ionization

Charge-exchange ionization (also called charge-transfer ionization) is a gas phase reaction between an ion

Ion

and a neutral species

in which the charge of the ion is transferred to the neutral.

Chemical ionization

In chemical ionization, ions are produced through the reaction of ions of a reagent gas with other species. Some common reagent gases include: methane

Methane

Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...

, ammonia

Ammonia

Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

, and isobutane

Isobutane

Isobutane, also known as methylpropane, is an isomer of butane. It is the simplest alkane with a tertiary carbon. Concerns with depletion of the ozone layer by freon gases have led to increased use of isobutane as a gas for refrigeration systems, especially in domestic refrigerators and freezers,...

Chemi-ionization

Chemi-ionization can be represented by

where G is the excited state species (indicated by the superscripted asterisk), and M is the species that is ionized by the loss of an electron

Electron

to form the radical

Radical (chemistry)

Radicals are atoms, molecules, or ions with unpaired electrons on an open shell configuration. Free radicals may have positive, negative, or zero charge...

cation (indicated by the superscripted "plus-dot").

Penning ionization

Penning ionization refers to the interaction between a gas-phase excited-state atom or molecule G^* and a target molecule M resulting in the formation of a radical molecular cation M^+., an electron e⁻, and a neutral gas molecule G:

Penning ionization occurs when the target molecule has an ionization potential

Ionization potential

The ionization energy of a chemical species, i.e. an atom or molecule, is the energy required to remove an electron from the species to a practically infinite distance. Large atoms or molecules have a low ionization energy, while small molecules tend to have higher ionization energies.The property...

lower than the internal energy of the excited-state atom or molecule. Associative Penning ionization can also occur:

Fragmentation

There are many important dissociation

Dissociation (chemistry)

Dissociation in chemistry and biochemistry is a general process in which ionic compounds separate or split into smaller particles, ions, or radicals, usually in a reversible manner...

reactions that take place in the gas phase.

Collision-induced dissociation

CID (also called collisionally activated dissociation - CAD) is a method used to fragment molecular ion

Ion

s in the gas phase. The molecular ions collide with neutral gas molecules such as helium

Helium

Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...

, nitrogen

Nitrogen

Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

or argon

Argon

Argon is a chemical element represented by the symbol Ar. Argon has atomic number 18 and is the third element in group 18 of the periodic table . Argon is the third most common gas in the Earth's atmosphere, at 0.93%, making it more common than carbon dioxide...

. In the collision some of the kinetic energy is converted into internal energy

Internal energy

which results in fragmentation.

Charge remote fragmentation

Charge remote fragmentation is a type of covalent bond

Covalent bond

A covalent bond is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms. The stable balance of attractive and repulsive forces between atoms when they share electrons is known as covalent bonding....

breaking that occurs in a gas phase ion

Ion

in which the cleaved bond is not adjacent to the location of the charge.