observation pathlength, \(l_{\text{obs}}\)

in flame emission and absorption spectrometry
https://doi.org/10.1351/goldbook.O04271
The intersection of the optical axis and the observation space (in \(\mathrm{mm}\)).
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 1741 [Terms] [Paper]