Photoionization Calculation Rate in a Gaseous Medium

Photoionization of neutral gas molecules is speculated to play a key role in plasma formation. Fundamental spectral data taken from a low current nonthermal plasma in the vacuum ultraviolet (VUV) regime is used to directly calculate the photoionization source term as a function of pressure. Light emitted from plasma was measured in the wavelength range between 85 nm and 105 nm using a 1 m vacuum spectrometer. The photoionization model used is based upon the general formulation into integral representation described by Zheleznyak et al. A quantitative analysis of the results obtained by newly acquired experimental data at the Sandia Plasma Research Facility (PRF) and those gained from the simulation based on the modification of the classic integral model of Zheleznyak is performed. The full numerical integral for the production of electrons due to photoionization is performed and compared against the assumption in the original model. The satisfactory agreement of the photoionization function from modified model with that of original model has been demonstrated. Furthermore, more recent absorption cross section data (total and photoionization cross section) is used to compute the transport and absorption of photons. This modified model based upon experimental measurements will be used in a two-dimensional axisymmetric model to numerically investigate plasma formation.