This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.Laser-induced fluorescence and phosphorescence properties of gaseous acetone in argon are
measured and analyzed in a pressure ranging from 10(5) to 10(2) Pa, with the aim of analyzing by molecular
tagging velocimetry gas microflows in rarefied regimes which requires operation at low pressure. Acetone is
excited at a wavelength of 266 nm and immediately emits short lifetime fluorescence rapidly followed by
long lifetime phosphorescence. At atmospheric pressure, the early phosphorescence intensity is more than
600 times lower than the fluorescence one. The phosphorescence signal is rapidly decreasing with time,
closely following a power law. Both fluorescence and phosphorescence signals are decreasing with pressure.
The systematic analysis of fluorescence and phosphorescence of acetone molecules shows that although the
signal is dramatically reduced at low pressure, the on-chip integration technique and the optimization of the
acquisition parameters provide an exploitable signal for molecular tagging velocimetry in rarefied
microflows, in a Knudsen number range corresponding to the early slip flow regime