The total absorption of radiation in the 2000-2800 Å region has been measured for ${\mathrm{O}}_2$. The absorption does not follow Beer's law. The linear increase in the measured effective absorption cross section with rise in gas pressure is ascribed to the absorption caused by ${\mathrm{O}}_4$. With methods developed and presented recently by the writer, the absorption cross sections of ${\mathrm{O}}_2$ and ${\mathrm{O}}_4$ are derived from total absorption measurements.

• Received 17 February 1969

DOI:https://doi.org/10.1103/PhysRev.186.5