Speaker
Description
This analysis doesn't seek to create the most complex and definitive Ar/Hydrogen chemistry and radiation model, but rather to gain enough insight from existing literature to support an easily manageable chemistry set, within a more complex transport code, assessing the plasma species dynamics and radiation rates required to infer line intensities for experimental actinometry.
No matter what details of the chemistry rate scheme, a plasma chemistry model can be represented by a straightforward set of (mostly) binary rate equations combining creation $\it C$ and destruction $\it D$ operators for all species.
${\dot f}_k=f_if_j({\it C}_{ijk}-{\it D}_{ijk})-{\it A}_{{\lambda}k}f_k$
The mole fractions $f_k$ are dimensionless fractions decomposing unity and the creation or destruction operators are normalized to the (local) heavy particle density, $n_h$. In the special case of three body destruction or recombination processes, the ${\it D}_{ijk}→f_h•_h{\it D}_{ijk}$ with $f_h$ the vector of heavy particle species. For non-LTE electrons, $f_e$ is further decomposed into a electron energy distribution function (EEDF), viz. $f_e → f[e,\varepsilon]$ with the energy grid $\varepsilon$ spanning the electron phase space generated by a known value of electric field over total density, viz. $E/n_h$. Each $\it C$ or $\it D$ operator then becomes a convolution of the EEDF with a particular cross section for the process of interest, viz. ${\it C}_{ejk}(E/n)=\int{\sigma}_{jk}(\varepsilon)•f_e[e,\varepsilon]$. Finally, the radiative decay channels, ${\it A}_{{\lambda}k}f_k$, diminish the mole fraction of excited states, providing emission intensities for the observed wavelengths $\lambda$.
Generally the Boltzmann modeled EEDF achieves (~10 ns) a steady state with respect to creation, radiation and recombination in the discharge medium for virtually any specified values $[E/n,f_h,f_e]$ — defining all of the rate coefficients and transport coefficients dependence on $f_k$. Using the frequency shift in RF cavity modes together with the actinometry data, it is expected that a more precise electron density can be inferred.
