# Curve of growth

From AMS Glossary

## curve of growth

For an isolated, gaseous absorption band, the relation between integrated absorption by the gas and its amount.

That is, if where κ is the (volumetric) absorption coefficient of the gas,

*x*is the path length through it, and the range of integration over frequency ν is sufficient to include essentially all absorption within the band, then*W*as a function of*x*is the curve of growth. This term, which Goody describes as "curious," is a relic from astronomical spectroscopy.Goody, R. M. 1964. Atmospheric Radiation. Vol. 1, . p. 125.