  We performed a time-resolved spectroscopic study of the VUV/UV argon
scintillation as a function of pressure and electric field, by means of a
wavelength sensitive detector operated with different radioactive sources. Our
work conveys new evidence of distinctive features of the argon light which are
in contrast with the general assumption that, for particle detection purposes,
the scintillation can be considered to be largely monochromatic at 128 nm
(second continuum). The wavelength and the time-resolved analysis of the photon
emission reveal that the dominant component of the argon scintillation during
first tens of ns is in the range [160, 325] nm. This light is consistent with
the third continuum emission from highly charged argon ions/molecules. This
component of the scintillation is field-independent up to 25 V/cm/bar and shows
a very mild dependence with pressure in the range [1,16] bar. The dynamics of
the second continuum emission is dominated by the excimer formation time, whose
variation as a function of the pressure has been measured. Additionally, the
time and pressure-dependent features of electron-ion recombination, in the
second continuum band, have been measured. This study opens new paths toward a
novel particle identification technique based on the spectral information of
the noble-elements scintillation light.
