Atomic oxygen ground state density is measured in the time afterglow o
f a pulsed discharge with resonant absorption spectroscopy in the vacu
um ultraviolet range. The evolution of atomic density during the after
glow is a sum of two exponential decays. The recombination probability
at the pyrex wall of the discharge tube is deduced from the fastest d
ecay. The so obtained value is gamma = (2.4 +/- 1.1) x 10(-3). Interpr
etations of the slowest decay as possible atomic gain are brought up i
n the discussion.