Pressure broadening of O2 in the a 1Δg state

The pressure broadening coefficient for O2 in the a 1Δg state has been measured to be 2.006±0.064 MHz/Torr at 290 K with a submillimeter-wave spectrometer with a backward wave oscillator as radiation source, where the uncertainty indicates one standard error from a least-squares fit. The broadening parameter by nitrogen is also measured. The temperature dependence is examined in the range 246–290 K. These results are useful for deriving the altitude distribution of O2 a 1Δg generated by a photochemical reaction from ozone in the upper stratosphere and mesosphere.