Hydrogen ion cluster
Encyclopedia
A hydrogen molecular ion cluster or hydrogen cluster ion is a positively charged cluster of hydrogen molecules. The hydrogen molecular ion
(H2+) and trihydrogen ion (H3+) are well defined molecular species. However hydrogen also forms singly charged clusters (Hn+) with n up to 120.
H6+ is stable in solid hydrogen
. The positive charge is balanced by a solvated electron. It is formed when ionizing radiation impinges on solid hydrogen
, and so is formed in radioactive solid tritium
. In natural hydrogen treated with radiation, the positive charge transfers to HD molecules with the ultimate most stable arrangement being HD(HD)+HD. H6+ can migrate though solid hydrogen by linking a hydrogen molecule at one end and losing it at the other: H2 + H6+ → H6+ + H2. This migration stops once a HD molecule is added to the resultant lower energy level. HD or D2 is added in preference over H2.
Clampitt and Gowland found odd number of hydrogen atoms H3+2n+ and later showed that H15+ was relatively stable. H3+ formed the core of this cluster with six H2 molecules surrounding it.
Hiroka studied the stability of the odd numbered clusters in gas up to H21+.
Bae determined that H15+ was especially stable amongst the odd numbered clusters.
Kirchner discovered even numbered atomic clusters in gas at lower concentrations than the odd numbered atom clusters. H6+ was twenty times less abundant than H5+. H4+ H8+ and H10+ were detected at lesser amounts than H6+.
Kurosaki and Takayanagi showed that H6+ is much more stable than other even clusters and showed antiprismatic symmetry of order 4 (D2d molecular symmetry
). This turnstyle structured molecule was computationally found to be more energetically stable than a ring of five hydrogen atoms around a proton.
Negative hydrogen clusters have not been found to exist. H3- is theoretically unstable, but D3- in theory is bound at 0.003 eV.
Positive ion clusters are also formed when compressed hydrogen expands though a nozzle.
Kirchner's theory for the formation of even numbered clusters was that neutral H3 molecules reacted the H3+ ion (or other odd clusters) to make H6+.
of 600 s with only 2% concentration of ions. However they could not contain the H- in a stable way, but determined that other negative ions would do as well. This theoretical impulse exceeds that of solid and liquid fuel rockets. SRI developed a cluster ion gun that could make positive and negative ion clusters at a current of 500 pA.
Nuclear fusion using ion clusters can impact far more atoms than single ions in one hit. This concept is called cluster Ion fusion (CIF). Lithium deuteride (LiD) is a potential starter material for generating the ions.
Hydrogen molecular ion
The hydrogen molecular ion, dihydrogen cation, or H2+, is the simplest molecular ion. It is composed of two positively-charged protons and one negatively-charged electron, and can be formed from ionization of a neutral hydrogen molecule...
(H2+) and trihydrogen ion (H3+) are well defined molecular species. However hydrogen also forms singly charged clusters (Hn+) with n up to 120.
Experiments
These can be formed in liquid helium or with lesser cluster size in pure hydrogen. H6+ is far more common than higher even numbered clusters.H6+ is stable in solid hydrogen
Solid hydrogen
Solid hydrogen is the solid state of the element hydrogen, achieved by decreasing the temperature below hydrogen's melting point of 14.01 K . It was collected for the first time by James Dewar in 1899 and published with the title "Sur la solidification de l'hydrogène" in the Annales de Chimie et...
. The positive charge is balanced by a solvated electron. It is formed when ionizing radiation impinges on solid hydrogen
Solid hydrogen
Solid hydrogen is the solid state of the element hydrogen, achieved by decreasing the temperature below hydrogen's melting point of 14.01 K . It was collected for the first time by James Dewar in 1899 and published with the title "Sur la solidification de l'hydrogène" in the Annales de Chimie et...
, and so is formed in radioactive solid tritium
Tritium
Tritium is a radioactive isotope of hydrogen. The nucleus of tritium contains one proton and two neutrons, whereas the nucleus of protium contains one proton and no neutrons...
. In natural hydrogen treated with radiation, the positive charge transfers to HD molecules with the ultimate most stable arrangement being HD(HD)+HD. H6+ can migrate though solid hydrogen by linking a hydrogen molecule at one end and losing it at the other: H2 + H6+ → H6+ + H2. This migration stops once a HD molecule is added to the resultant lower energy level. HD or D2 is added in preference over H2.
Clampitt and Gowland found odd number of hydrogen atoms H3+2n+ and later showed that H15+ was relatively stable. H3+ formed the core of this cluster with six H2 molecules surrounding it.
Hiroka studied the stability of the odd numbered clusters in gas up to H21+.
Bae determined that H15+ was especially stable amongst the odd numbered clusters.
Kirchner discovered even numbered atomic clusters in gas at lower concentrations than the odd numbered atom clusters. H6+ was twenty times less abundant than H5+. H4+ H8+ and H10+ were detected at lesser amounts than H6+.
Kurosaki and Takayanagi showed that H6+ is much more stable than other even clusters and showed antiprismatic symmetry of order 4 (D2d molecular symmetry
Molecular symmetry
Molecular symmetry in chemistry describes the symmetry present in molecules and the classification of molecules according to their symmetry. Molecular symmetry is a fundamental concept in chemistry, as it can predict or explain many of a molecule's chemical properties, such as its dipole moment...
). This turnstyle structured molecule was computationally found to be more energetically stable than a ring of five hydrogen atoms around a proton.
Negative hydrogen clusters have not been found to exist. H3- is theoretically unstable, but D3- in theory is bound at 0.003 eV.
Decay
H6+ in the free gas state decays by giving off H atoms and H2 molecules. Different energies of decay occur with levels averaging at 0.038 eV and peaking at 0.14 eV.Formation
Hydrogen molecular ion clusters can be formed through different kinds of ionizing radiation. High energy electrons capable of ionizing the material can perform this task. When hydrogen dissolved in liquid helium is irradiated with electrons their energy must be sufficient to ionize helium to produce significant hydrogen clusters. Irradiation of solid hydrogen by gamma rays or X-rays also produces H6+.Positive ion clusters are also formed when compressed hydrogen expands though a nozzle.
Kirchner's theory for the formation of even numbered clusters was that neutral H3 molecules reacted the H3+ ion (or other odd clusters) to make H6+.
Properties
Solvation of H6+ in solid hydrogen had little effect on its spectrum.Use
SRI International studied solid ionic hydrogen fuel. The believed that a solid containing H3+ and H- ions could be manufactured. If it could be made it would have a higher energy than other rocket fuels with a specific impulseSpecific impulse
Specific impulse is a way to describe the efficiency of rocket and jet engines. It represents the derivative of the impulse with respect to amount of propellant used, i.e., the thrust divided by the amount of propellant used per unit time. If the "amount" of propellant is given in terms of mass ,...
of 600 s with only 2% concentration of ions. However they could not contain the H- in a stable way, but determined that other negative ions would do as well. This theoretical impulse exceeds that of solid and liquid fuel rockets. SRI developed a cluster ion gun that could make positive and negative ion clusters at a current of 500 pA.
Nuclear fusion using ion clusters can impact far more atoms than single ions in one hit. This concept is called cluster Ion fusion (CIF). Lithium deuteride (LiD) is a potential starter material for generating the ions.