List of molecules in interstellar space

This is a list of molecules that have been detected in the interstellar medium, grouped by the number of component atoms. The chemical formula is listed for each detected compound, along with any ionized form that has also been observed.

Detection

The molecules listed below were detected by spectroscopy. Their spectral features are generated by transitions of component electrons between different energy levels, or by rotational or vibrational spectra. Detection usually occurs in radio, microwave, or infrared portions of the spectrum. [cite book
first=Frank H. | last=Shu | year=1982
title=The Physical Universe: An Introduction to Astronomy
publisher=University Science Books
isbn=0935702059 ] The first such molecule to be detected in the interstellar medium was the methylidyne radical (CH) in 1937. [cite web
last = Woon | first = D. E. | date = May, 2005
url = http://www.astrochymist.org/AMOTM/amotm_0505.html
title = Methylidyne radical | publisher = The Astrochemist
accessdate = 2007-02-13 ]

Interstellar molecules are formed by chemical reactions within very sparse interstellar or circumstellar clouds of dust and gas. Usually this occurs when a molecule becomes ionized, often as the result of an interaction with a cosmic ray. This positively-charged molecule then draws in a nearby reactant by electrostatic attraction of the neutral molecule's electrons. Molecules can also be generated by reactions between neutral atoms and molecules, although this process is generally slower. [cite journal
last=Dalgarno | first=A.
title=Interstellar Chemistry Special Feature: The galactic cosmic ray ionization rate
journal=Proceedings of the National Academy of Science
year=2006 | volume=103 | issue=33 | pages=12269–12273
url=http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1567869
accessdate=2008-03-09 | doi=10.1073/pnas.0602117103
pmid=16894166 ]

A particularly large and rich region for detecting interstellar molecules is Sagittarius B2 (Sgr B2). This giant molecular cloud lies near the center of the Milky Way galaxy and is a frequent target for new searches. About half of the molecules listed below were first found near Sgr B2, and nearly every other molecule has since been detected in this feature. [cite journal
author=S. E. Cummins, R. A. Linke, P. Thaddeus
title=A survey of the millimeter-wave spectrum of Sagittarius B2
journal=Astrophysical Journal Supplement Series
year=1986 | volume=60 | pages=819–878
url=http://adsabs.harvard.edu/abs/1986ApJS...60..819C
accessdate=2007-02-06 | doi=10.1086/191102]

Molecules

The following tables list molecules that have been detected in the interstellar medium, grouped by the number of component atoms. If there is no entry in the Molecule column, only the ionized form has been detected. For molecules where no designation was given in the scientific literature, that field is left empty.

Diatomic

, theprimary component of natural gas, has also been detected on comets and in the atmosphere of several planets in the author=A. L. Butterworth,O. Aballain, J. Chappellaz, M. A. Sephton | title=Combined element (H and C) stable isotope ratios of methane in carbonaceous chondrites | journal=Monthly Notices of the Royal Astronomical Society | year=2004 | volume=347 | issue=3 | pages=807–812 | url=http://adsabs.harvard.edu/abs/2004MNRAS.347..807B | accessdate=2007-02-16 | doi=10.1111/j.1365-2966.2004.07251.x]

Five atoms

Eight atoms

Deuterated molecules

These molecules all contain a deuterium atom.

Unconfirmed

The following molecules have been reported as detected in scientific literature, but they have not yet been confirmed through subsequent searches.

ee also

*Astrochemistry
*Chemistry
*Chemical formula
*Diffuse interstellar band
*Forbidden mechanism

References

External links

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