Positronium hydride, or hydrogen positride[3] is an exotic molecule consisting of a hydrogen atom bound to an exotic atom of positronium (that is a combination of an electron and a positron). Its formula is PsH. It was predicted to exist in 1951 by A Ore,[4] and subsequently studied theoretically, but was not observed until 1990. R. Pareja, R. Gonzalez from Madrid trapped positronium in hydrogen laden magnesia crystals. The trap was prepared by Yok Chen from the Oak Ridge National Laboratory.[5] In this experiment the positrons were thermalized so that they were not traveling at high speed, and they then reacted with H− ions in the crystal.[6] In 1992 it was created in an experiment done by David M. Schrader and F.M. Jacobsen and others at the Aarhus University in Denmark. The researchers made the positronium hydride molecules by firing intense bursts of positrons into methane, which has the highest density of hydrogen atoms. Upon slowing down, the positrons were captured by ordinary electrons to form positronium atoms which then reacted with hydrogen atoms from the methane.[7]
PsH is constructed from one proton, two electrons, and one positron. The binding energy is 1.1±0.2 eV. The lifetime of the molecule is 0.65 nanoseconds. The lifetime of positronium deuteride is indistinguishable from the normal hydride.[6]
The decay of positronium is easily observed by detecting the two 511 keV gamma ray photons emitted in the decay. The energy of the photons from positronium should differ slightly by the binding energy of the molecule. However, this has not yet been detected.[3]
Propertiesedit
The structure of PsH is as a diatomic molecule, with a chemical bond between the two positively charged centres. The electrons are more concentrated around the proton.[2] Predicting the properties of PsH is a four body Coulomb problem. Calculated using the stochastic variational method, the size of the molecule is larger than dihydrogen, which has a bond length of 0.7413 Å.[8] In PsH the positron and proton are separated on average by 3.66 a0 (1.94 Å). The positronium in the molecule is swollen compared to the positronium atom, increasing to 3.48 a0 compared to 3 a0. Average distance of the electrons from the proton is larger than the dihydrogen molecule, at 2.31 a0 with the maximum density at 2.8 au.[3]
Formationedit
Due to its short lifetime, establishing the chemistry of positronium hydride poses difficulties. Theoretical calculations can predict outcomes. One method of formation is through alkali metal hydrides reacting with positrons. Molecules with dipole moments greater than 1.625 debye are predicted to attract and hold positrons in a bound state. Crawford's model predicts this positron capture. In the case of lithium hydride, sodium hydride and potassium hydride molecules, this adduct decomposes and positronium hydride and the alkali positive ion form.[9]
M+H− + e+ → PsH + M+
Similar compoundsedit
PsH is a simple exotic compound. Other compounds of positronium are possible by the reactions e+ + AB → PsA + B+.[10] Other substances that contain positronium are di-positronium and the ion Ps− with two electrons. Molecules of Ps with normal matter include halides and cyanide.[2]
Positronium antihydride (PsH) contains antihydrogen instead of hydrogen. It can be made as the anti-hydride ion (H+) reacts with positronium (Ps)
H+ + Ps → PsH + e+
The GBAR experiment uses the similar reaction H + Ps → H+ + e− which cannot produce positronium antihydride, as there is too much energy left over for positronium antihydride to be stable.[11]
Referencesedit
^"positronium hydride". ebi.ac.uk. from the original on 2018-04-03. Retrieved 2017-07-21.
^ abcSaito, Shiro L. (2000). "Is Positronium Hydride Atom or Molecule?". Nuclear Instruments and Methods in Physics Research B. 171 (1–2): 60–66. Bibcode:2000NIMPB.171...60S. doi:10.1016/s0168-583x(00)00005-7.
^ abcUsukura, J.; K. Varga; Y. Suzuki (22 Apr 1998). "Signature of the existence of the positronium molecule". Physical Review A. 58 (3): 1918. arXiv:physics/9804023. Bibcode:1998PhRvA..58.1918U. doi:10.1103/PhysRevA.58.1918. S2CID 11941483.
^ Usukura, J.; Varga, K.; Suzuki, Y. (1998). "Signature of the existence of the positronium molecule". Physical Review A. 58 (3): 1918. arXiv:physics/9804023. Bibcode:1998PhRvA..58.1918U. doi:10.1103/PhysRevA.58.1918. S2CID 11941483.
^"FY 1992 Accomplishments - "Out of This World" Chemical Compound Observed" (PDF). p. 9.
^ abMonge, M. A.; R. Pareja; R. González; Y. Chen (1996). "Positronium deuteride and hydride in MgO crystals". Journal of Radioanalytical and Nuclear Chemistry. 211 (1): 23–29. doi:10.1007/BF02036251. ISSN 0236-5731. S2CID 96576192.
^ Schrader, D. M.; Jacobson, Finn M.; Niels-Peter, Niels-Peter; Mikkelsen, Ulrik (1992). "Formation of Positronium Hydride". Physical Review Letters. 69 (1): 57–60. Bibcode:1992PhRvL..69...57S. doi:10.1103/PhysRevLett.69.57. PMID 10046188.
^"Bond lengths and dissociation enthalpies of diatomic molecules". National Physics Laboratory Kaye and Laby tables of physical and chemical constants.
^Oyamada, Takayuki; Masanori Tachikawa (2014). "Multi-component molecular orbital study on positron attachment to alkali-metal hydride molecules: nature of chemical bonding and dissociation limits of [LiH; e+]". The European Physical Journal D. 68 (8): 231. Bibcode:2014EPJD...68..231O. doi:10.1140/epjd/e2014-40708-4. ISSN 1434-6060. S2CID 119703798.
^Schrader, D. M. (1992). "Positronium hydride formation in collisions of positrons with molecular hydrogen". Theoretica Chimica Acta. 82 (5): 425–434. doi:10.1007/BF01113943. ISSN 0040-5744. S2CID 95698790.
^Froelich, Piotr (30 July 2023). Formation of the postronium antihydride molecules in low energy, 5-body collisions. 25th European Conference on Few-Body Problems in Physics.
Extra readingedit
Zhang, Yi; Yan, Guo-An (25 March 2024). "P-Wave Doubly Excited States of Positronium Hydride". International Journal of Theoretical Physics. 63 (3): 80. Bibcode:2024IJTP...63...80Z. doi:10.1007/s10773-024-05596-w.
Masood, Iraj; Munir, S. Zayad; Aslam, M. Jamil (25 March 2024). "Contribution of various spin configurations to the radiationless decay of PsH". Physical Review A. 109 (3): 032820. Bibcode:2024PhRvA.109c2820M. doi:10.1103/PhysRevA.109.032820.
January 01, 1970
positronium, hydride, hydrogen, positride, exotic, molecule, consisting, hydrogen, atom, bound, exotic, atom, positronium, that, combination, electron, positron, formula, predicted, exist, 1951, subsequently, studied, theoretically, observed, until, 1990, pare. Positronium hydride or hydrogen positride 3 is an exotic molecule consisting of a hydrogen atom bound to an exotic atom of positronium that is a combination of an electron and a positron Its formula is PsH It was predicted to exist in 1951 by A Ore 4 and subsequently studied theoretically but was not observed until 1990 R Pareja R Gonzalez from Madrid trapped positronium in hydrogen laden magnesia crystals The trap was prepared by Yok Chen from the Oak Ridge National Laboratory 5 In this experiment the positrons were thermalized so that they were not traveling at high speed and they then reacted with H ions in the crystal 6 In 1992 it was created in an experiment done by David M Schrader and F M Jacobsen and others at the Aarhus University in Denmark The researchers made the positronium hydride molecules by firing intense bursts of positrons into methane which has the highest density of hydrogen atoms Upon slowing down the positrons were captured by ordinary electrons to form positronium atoms which then reacted with hydrogen atoms from the methane 7 Positronium hydride Names IUPAC name Positronium hydride Identifiers 3D model JSmol Interactive image ChEBI CHEBI 46711 SMILES Ps H Properties Chemical formula PsH Molar mass 1 00794 1 Appearance Maybe gas Structure Molecular shape Diatomic molecule 2 Except where otherwise noted data are given for materials in their standard state at 25 C 77 F 100 kPa Infobox references Contents 1 Decay 2 Properties 3 Formation 4 Similar compounds 5 References 6 Extra readingDecay editPsH is constructed from one proton two electrons and one positron The binding energy is 1 1 0 2 eV The lifetime of the molecule is 0 65 nanoseconds The lifetime of positronium deuteride is indistinguishable from the normal hydride 6 The decay of positronium is easily observed by detecting the two 511 keV gamma ray photons emitted in the decay The energy of the photons from positronium should differ slightly by the binding energy of the molecule However this has not yet been detected 3 Properties editThe structure of PsH is as a diatomic molecule with a chemical bond between the two positively charged centres The electrons are more concentrated around the proton 2 Predicting the properties of PsH is a four body Coulomb problem Calculated using the stochastic variational method the size of the molecule is larger than dihydrogen which has a bond length of 0 7413 A 8 In PsH the positron and proton are separated on average by 3 66 a0 1 94 A The positronium in the molecule is swollen compared to the positronium atom increasing to 3 48 a0 compared to 3 a0 Average distance of the electrons from the proton is larger than the dihydrogen molecule at 2 31 a0 with the maximum density at 2 8 au 3 Formation editDue to its short lifetime establishing the chemistry of positronium hydride poses difficulties Theoretical calculations can predict outcomes One method of formation is through alkali metal hydrides reacting with positrons Molecules with dipole moments greater than 1 625 debye are predicted to attract and hold positrons in a bound state Crawford s model predicts this positron capture In the case of lithium hydride sodium hydride and potassium hydride molecules this adduct decomposes and positronium hydride and the alkali positive ion form 9 M H e PsH M Similar compounds editPsH is a simple exotic compound Other compounds of positronium are possible by the reactions e AB PsA B 10 Other substances that contain positronium are di positronium and the ion Ps with two electrons Molecules of Ps with normal matter include halides and cyanide 2 Positronium antihydride PsH contains antihydrogen instead of hydrogen It can be made as the anti hydride ion H reacts with positronium Ps H Ps PsH e The GBAR experiment uses the similar reaction H Ps H e which cannot produce positronium antihydride as there is too much energy left over for positronium antihydride to be stable 11 References edit positronium hydride ebi ac uk Archived from the original on 2018 04 03 Retrieved 2017 07 21 a b c Saito Shiro L 2000 Is Positronium Hydride Atom or Molecule Nuclear Instruments and Methods in Physics Research B 171 1 2 60 66 Bibcode 2000NIMPB 171 60S doi 10 1016 s0168 583x 00 00005 7 a b c Usukura J K Varga Y Suzuki 22 Apr 1998 Signature of the existence of the positronium molecule Physical Review A 58 3 1918 arXiv physics 9804023 Bibcode 1998PhRvA 58 1918U doi 10 1103 PhysRevA 58 1918 S2CID 11941483 Usukura J Varga K Suzuki Y 1998 Signature of the existence of the positronium molecule Physical Review A 58 3 1918 arXiv physics 9804023 Bibcode 1998PhRvA 58 1918U doi 10 1103 PhysRevA 58 1918 S2CID 11941483 FY 1992 Accomplishments Out of This World Chemical Compound Observed PDF p 9 a b Monge M A R Pareja R Gonzalez Y Chen 1996 Positronium deuteride and hydride in MgO crystals Journal of Radioanalytical and Nuclear Chemistry 211 1 23 29 doi 10 1007 BF02036251 ISSN 0236 5731 S2CID 96576192 Schrader D M Jacobson Finn M Niels Peter Niels Peter Mikkelsen Ulrik 1992 Formation of Positronium Hydride Physical Review Letters 69 1 57 60 Bibcode 1992PhRvL 69 57S doi 10 1103 PhysRevLett 69 57 PMID 10046188 Bond lengths and dissociation enthalpies of diatomic molecules National Physics Laboratory Kaye and Laby tables of physical and chemical constants Oyamada Takayuki Masanori Tachikawa 2014 Multi component molecular orbital study on positron attachment to alkali metal hydride molecules nature of chemical bonding and dissociation limits of LiH e The European Physical Journal D 68 8 231 Bibcode 2014EPJD 68 231O doi 10 1140 epjd e2014 40708 4 ISSN 1434 6060 S2CID 119703798 Schrader D M 1992 Positronium hydride formation in collisions of positrons with molecular hydrogen Theoretica Chimica Acta 82 5 425 434 doi 10 1007 BF01113943 ISSN 0040 5744 S2CID 95698790 Froelich Piotr 30 July 2023 Formation of the postronium antihydride molecules in low energy 5 body collisions 25th European Conference on Few Body Problems in Physics Extra reading editZhang Yi Yan Guo An 25 March 2024 P Wave Doubly Excited States of Positronium Hydride International Journal of Theoretical Physics 63 3 80 Bibcode 2024IJTP 63 80Z doi 10 1007 s10773 024 05596 w Masood Iraj Munir S Zayad Aslam M Jamil 25 March 2024 Contribution of various spin configurations to the radiationless decay of PsH Physical Review A 109 3 032820 Bibcode 2024PhRvA 109c2820M doi 10 1103 PhysRevA 109 032820 Retrieved from https en wikipedia org w index php title Positronium hydride amp oldid 1224846155, wikipedia, wiki, book, books, library,
