[en] The irradiation of atmospheric air with high-energy protons has been performed at the 12 GeV proton synchrotron. The specific activity of ¹³N, one of the principal airborne radioactivities, was measured as a function of the irradiation time at a dose rate of about 6 x 10¹⁶ eV/g/s, and compared with the calculated values. The predominant chemical species of ¹³N produced were found to be ¹³N₂ and ¹³NO₂. Their proportions were approximately 55% for ¹³N₂ and 45% for ¹³NO₂, being almost independent of the irradiation time. Smaller quantities of ¹³NO and H¹³NO₂ were also observed. Measurements of radiolytic products showed that ozone is a main product and that NO₂ predominates among the products of nitrogen compounds, including HNO₂ and HNO₃. The G-value for ozone formation in air was estimated from the experimental data as 6.4 molecules/100 eV. (author)