  Controlling fluxes of vacuum ultraviolet (VUV) radiation is important in a
number of industrial and biomedical applications of low pressure plasma sources
because, depending on the process, VUV radiation may be desired, required to a
certain degree, or unwanted. In this work, the emission of VUV radiation from O
atoms is investigated in low-pressure Ar/O$_2$ inductively coupled plasma via
numerical simulations. For this purpose, a self-consistent Ar/O$_2$
plasma-chemical reaction scheme has been implemented in a zero dimensional
plasma chemical kinetics model and is used to investigate VUV emission from
excited O atoms (3s $^5$S$^0_2$) and 3s $^3$S$^0_1$) at 130 and 135 nm. The
model is extensively compared with experimental measurements of absolute VUV
emission intensities, electron densities and Ar excited state densities. In
addition, VUV emission intensities are investigated as a function of pressure,
Ar/O$_2$ mixture, and power deposition and the dominant reaction pathways
leading to VUV emission are identified and described. In general terms,
absolute VUV emission intensities increase with power and oxygen fraction over
the ranges investigated and peak emission intensities are found for pressures
between 5-50 Pa. The emission is dominated by the 130 nm resonance line from
the decay of the O(3s $^3$S$^0_1$) state to the ground state. Besides, at low
pressure (0.3-1 Pa), the flux of VUV photons to surfaces is much lower than
that of positive ions, whereas VUV fluxes dominate at higher pressure,
$\gtrsim$5-50 Pa depending on O$_2$ fraction. Finally, oxygen atom fluxes to
surfaces are, in general, larger than those of VUV photons for the parameter
space investigated.
