Physics:Fluoromethylidynium
Fluoromethylidynium or carbon monofluoride cation is a cation with molecular formula CF+. It has gained prominence due to its discovery in space.[1]
Natural occurrence
Fluoromethylidynium was discovered in the Orion Bar. Here the surface density of CF+ molecules is over 1012 cm-2 over a space of a square minute of arc. The IRAM 30 m and APEX 12 m telescopes were used.[2] In the Horsehead Nebula photo-dissociation region the density was observed to be 1.5-2.0 × 1012 cm-2.[3] In molecular clouds CF+ contains about 1% of the fluorine, with the rest being in HF molecules. CF+ has been detected in the N113 star forming region of the Large Magellanic Cloud.[4]
Absorption lines for CF+ have been observed in the direction of BL Lacertae, 3C 111 and Westerhout 49, where the Milky Way interstellar medium is backlit by sources bright in the millimeter wave range.[5] CF+ has been detected in a collapsing protostar envelope.[6]
Production
The hypothesised method of formation of CF+ in gas clouds in space is by a reaction of the carbon anion with hydrogen fluoride.[2]
- C+ + HF → H• + CF+
C+ forms on the edge of a nebula, where ultraviolet rays can ionise carbon. HF forms in a reaction with atomic fluorine with molecular hydrogen H2.[3] In the laboratory, CF+ can be made by an electric discharge in hexafluoroethane diluted with helium.[7]
Properties
| transition | frequency
GHz |
strength |
|---|---|---|
| J=1-0 | 102.58748 | |
| J=2-1 | 205.17445 | |
| J=3-2 | 307.74438 |
The singlet ground state is designated: X1Σ+ and the first electronically triplet excited state is: a3Π.[8] The internuclear distance in the ground state is 1.159 Å.[9] Molecular parameters measured from the spectrum are: ωe = 1792.665 cm−1, Be = 1.720417 cm−1, Y20, = −13.2297 cm−1, and D0 = 6209 cm−1.[7] CF+ is isoelectronic with BF, CO and CN−.[3]
Most of the charge on CF+ is concentrated on the carbon atom. Calculations show +0.90116 on carbon and +0.09884 on fluorine.[10]
Reactions
CF+ binds helium atoms weakly. Computational studies suggest the helium atom is bound roughly perpendicularly to the C-F bond, angled towards the carbon atom at 99.4° from the centre of mass at a position of 5.17 bohr. The binding energy is calculated to be –212.192 cm−1 (26.3 meV, 2.5383798 kJ/mol).[10]
In dissociative recombination an electron combines and the molecule breaks up.[11]
- CF+ + e− → C + F•
References
- ↑ "ASTROMOLECULE OF THE MONTH". https://www.astrochymist.org/AMOTM/amotm_1405.html.
- ↑ 2.0 2.1 Neufeld, D. A.; Schilke, P.; Menten, K. M.; Wolfire, M. G.; Black, J. H.; Schuller, F.; Müller, H. S. P.; Thorwirth, S. et al. (August 2006). "Discovery of interstellar CF+". Astronomy & Astrophysics 454 (2): L37–L40. doi:10.1051/0004-6361:200600015.
- ↑ 3.0 3.1 3.2 Guzmán, V.; Pety, J.; Gratier, P.; Goicoechea, J. R.; Gerin, M.; Roueff, E.; Teyssier, D. (July 2012). "The IRAM-30m line survey of the Horsehead PDR: I. CF+ as a tracer of C+ and as a measure of the fluorine abundance". Astronomy & Astrophysics 543: L1. doi:10.1051/0004-6361/201219449. ISSN 0004-6361.
- ↑ Morino, Isamu; Yamada, Koichi M. T.; Belov, Sergei P.; Winnewisser, Gisbert; Herbst, Eric (20 March 2000). "The CF Radical: Terahertz Spectrum and Detectability in Space". The Astrophysical Journal 532 (1): 377–383. doi:10.1086/308543. Bibcode: 2000ApJ...532..377M.
- ↑ Liszt, H. S.; Guzmán, V. V.; Pety, J.; Gerin, M.; Neufeld, D. A.; Gratier, P. (July 2015). "Widespread galactic CF+ absorption: detection toward W49 with the Plateau de Bure Interferometer". Astronomy & Astrophysics 579: A12. doi:10.1051/0004-6361/201526232.
- ↑ Fechtenbaum, S.; Bontemps, S.; Schneider, N.; Csengeri, T.; Duarte-Cabral, A.; Herpin, F.; Lefloch, B. (February 2015). "First detection of CF+ towards a high-mass protostar". Astronomy & Astrophysics 574: L4. doi:10.1051/0004-6361/201424718. Bibcode: 2015A&A...574L...4F.
- ↑ 7.0 7.1 Gruebele, Martin; Polak, Mark; Saykally, Richard J. (March 1986). "Velocity modulation laser spectroscopy of vibrationally excited CF+ determination of the molecular potential function". Chemical Physics Letters 125 (2): 165–169. doi:10.1016/0009-2614(86)85096-5.
- ↑ McCarver, Gavin A.; Hinde, Robert J. (2024-01-25). "High Accuracy Ab Initio Potential Energy Curves and Dipole Moment Functions for the X1Σ+ and a3Π Spin States of the CF+ Diatomic Molecule" (in en). The Journal of Physical Chemistry A 128 (3): 539–547. doi:10.1021/acs.jpca.3c04517. ISSN 1089-5639. PMID 38227217. Bibcode: 2024JPCA..128..539M.
- ↑ Inostroza, N.; Letelier, J.R.; Senent, M.L.; Fuentealba, P. (December 2008). "Theoretical ro-vibrational spectrum of CF+". Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 71 (3): 798–802. doi:10.1016/j.saa.2008.02.027. PMID 18378187.
- ↑ 10.0 10.1 Ajili, Y.; Hammami, K. (August 2013). "Induced rotational excitation of the fluoromethylidynium 12CF+ and 13CF+ through collision with helium". Astronomy & Astrophysics 556: A82. doi:10.1051/0004-6361/201220913.
- ↑ Forer, Joshua; Boffelli, Jeoffrey; Ayouz, Mehdi; Hvizdoš, Dávid; Kokoouline, Viatcheslav; Schneider, Ioan F.; Greene, Chris H. (2 October 2024). "Dissociative recombination of CF+". Physical Review A 110 (4). doi:10.1103/PhysRevA.110.L040801.
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