A curve of growth method was used to measure the integrated intensity of the 1-1-11 rotational line of the ν2 fundamental band of H2O. All measurements were taken at a temperature of 523°K, with pressures varying between 0.2–5 atm. By neglecting vibration-rotation interaction, the total band intensity was derived for which a value of Sband = 220 ± 22 cm-2 atm-1 at NPT was found.
A. Goldman and U. P. Oppenheim, "Integrated Intensity of the 6.3-µ Band of Water Vapor," Appl. Opt. 5, 1073-1074 (1966)