Astrophysics (Index)About

CO ladder

(CO rotational ladder, CO J ladder)
(series of CO rotational spectral lines)

The CO ladder (aka CO rotational ladder or CO J ladder) is a carbon monoxide (CO) series of rotational spectral lines, i.e., stemming from the steps in CO's possible rotational energy (CO transitions), modeled by:

       J(J+1)ℏ²
Erot = ————————
          2I

where Erot is the energy level, I is the moment of inertia of a CO molecule, ℏ is the reduced Planck constant, and J is 0, 1, 2, etc. The frequencies of lines produced by stepping up or down these energy levels are multiples of an increment near 115 GHz. The lines are typically identified by this form: CO(number-number), with the two numbers indicating two successive values of J. Lines of interest include:

CO(7-6)806.7 GHz0.37 mm
CO(6-5)691.473 GHz0.43 mm
CO(5-4)576.3 GHz0.52 mm
CO(4-3)461.0 GHz0.65 mm
CO(3-2)345.8 GHz0.87 mm
CO(2-1)230.5 GHz1.3 mm
CO(1-0)115.3 GHz2.6 mm
13CO(1-0)110.2 GHz2.72 mm

These can be detected in distant galaxies (e.g., z=1) within the millimeter/submillimeter range (e.g., submillimeter galaxies), and suggest gas clouds, i.e., indicating starburst galaxies and possibly mergers. CO lines, such CO(1-0) are useful for determining redshifts. CO(6-5) is used for observing protoplanetary disks and very distant (z>6) molecular clouds. Observations of multiple such lines (yielding their spectral line energy distribution (SLED)), can yield qualities of the gas, in particular, its temperature.


(chemistry,line series)
Further reading:
https://en.wikipedia.org/wiki/Rotational_spectroscopy
https://dictionary.obspm.fr/index.php?formSearchTextfield=co+ladder&showAll=1
https://www.cv.nrao.edu/~sransom/web/Ch7.html
https://sci.tanta.edu.eg/files/Microwave%20spectroscopy%20BSc-Lect-2.pdf
http://www-astro.physics.ox.ac.uk/~garret/teaching/rad-proc-lec-7.pdf
http://ned.ipac.caltech.edu/level5/Sept17/Carilli/Carilli2.html
https://ned.ipac.caltech.edu/level5/Sept15/Casey/Casey8.html
https://ned.ipac.caltech.edu/level5/Sept10/Krumholz/Krumholz2.html
https://ui.adsabs.harvard.edu/abs/2001ApJ...547..792D/abstract
https://ui.adsabs.harvard.edu/abs/2015A%26A...576A.109Y/abstract
WaveLFreqPhoton
Energy
  
261μm1150GHz4.8meVbeginCO ladder
2.7mm115GHz476μeVendCO ladder

Referenced by pages:
carbon monoxide (CO)
COMAP
intensity mapping surveys
spectral line designation

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