The vertical component of the velocity of the volatilized component in the observation
space
(in

).
It depends on the flame temperature, the solute nebulized, the observation height
and the gas flow rate.
Source:
PAC, 1986, 58, 1737
(Quantities and units in clinical chemistry: Nebulizer and flame properties in flame
emission and absorption spectrometry (Recommendations 1986))
on page 1742