Calcium monohydride
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IUPAC name
Calcium monohydride
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| Other names
Calcium(I) hydride
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3D model (Jmol)
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| ChemSpider | |
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PubChem CID
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| Properties | |
| CaH | |
| Molar mass | 41.085899 g/mol |
| Appearance | glowing red gas |
| reacts violently | |
| Related compounds | |
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Other cations
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Beryllium monohydride, Magnesium monohydride, Strontium monohydride, Barium monohydride, Potassium hydride |
| Calcium hydride | |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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| Infobox references | |
Calcium monohydride is a molecule composed of calcium and hydrogen with formula CaH. It can be found in stars as a gas formed when calcium atoms are present with hydrogen atoms.
Calcium monohydride was first discovered when its spectrum was observed in Alpha Herculis and ο Ceti by Alfred Fowler in 1907. It was observed in sunspots the following year by C. M. Olmsted. Next, it was made in a laboratory in 1909 by A. Eagle, and with early research by Hulthèn, and Watson and Weber in 1935. It was further observed in M dwarfs by Y. Öhman in 1934. Öhman proposed its use as a proxy for stellar luminosity, similar to magnesium monohydride (MgH), in being more apparent in the spectra of compact, cool, high surface gravity stars such as M dwarfs than in cool, low surface gravity stars such as M giants of non-negligible, or even comparable, metallicity.
Calcium monohydride is the first molecular gas that was cooled by a cold buffer gas and then trapped by a magnetic field. This extends the study of trapped cold atoms such as rubidium to molecules.
Calcium monohydride can be formed by exposing metallic calcium to an electric discharge in a hydrogen atmosphere above 750 °C. Below this temperature the hydrogen is absorbed to form calcium hydride.
Calcium monohydride can be formed by laser ablation of calcium dihydride in a helium atmosphere.
Gaseous calcium reacts with formaldehyde at temperatures around 1200 K to make CaH as well as some CaOH and CaO. This reaction glows orange-red.
The dipole moment of the CaH molecule is 2.94 debye. Spectrographic constants have been measured as bond length Re=2.0025 Å dissociation energy De=1.837 eV and harmonic vibrational frequency ωe=1298.34 cm−1. Ionisation potential is 5.8 eV. Electron affinity is 0.9 eV.
The ground state is X2Σ+.
The electronic states are:
B2Σ, with ν'=0 ← X2Σ with ν"=0 634 nm (or is it 690 nm?) CaH fluoresces with 634 nm light giving 690 nm emissions.
B2Σ+ ← X2Σ+ 585.8 nm to 590.2 nm.
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