The [Formula: see text] band at a wavelength of 1.58 μ has been observed with a scanning Fabry–Perot system in the evening twilight airglow at 45.2 °N. The decay time constant at a solar depression angle of 10° was about 45 minutes during the winter and about 30 minutes during the summer. The brightness at a solar depression angle of 6° was about 25 kR for both seasons. The emission could not be detected in the morning twilight. Theoretical solutions were obtained for an oxygen–hydrogen atmosphere to explain the observed behavior of the emission, with the assumption that excitation of the O2(1Δg) state is mainly due to photodissociation of ozone in the Hartley continuum. The results indicate that the ozone dissociation mechanism is probably the correct one. Formation of the O2(1Δg) state by three-body recombination of atomic oxygen has also been included to explain the observed emission of the [Formula: see text] 0,0 band at a wavelength of 1.27 μ in the night airglow. The evening twilight seasonal brightness variations of the 1.27 μ and 1.58 μ bands observed with ground-based instruments have not been satisfactorily explained.