How do you calculate the thermal width in velocity units?

08 August 2014 1 8K Report

Given a particular kinetic temperature of a medium, what is the correct formula to use to calculate the thermal contribution to the linewidth of a spectral line?

Robert Loughnane

The thermal contribution to the linewidth, dependent upon the kinetic temperature of the observed region and the molecular weight of the observed species is given by the following:

vth = sqrt(8(ln 2)kTkin/mmol)

The thermal and microturbulent contribution add in quadrature to give the full linewidth, at half the maximum value (FWHM).

SOURCE: "Maser Sources in Astrophysics" by Dr. Malcolm Gray

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