To predict the ionization and recombination through the less ionized stages, the model was extended to include kinetics models for all ion stages and the code is named as FLYCHK. The code is developed into a straightforward, rapid tool to provide ionization and population distributions of plasmas in zero dimension with accuracy sufficient for most initial estimates and in many cases is applicable for more sophisticated analysis.

Numerous experimental and calculational comparisons performed in recent years show that FLYCHK provides meaningful estimates of ionization distributions for most laboratory applications. Since 2006, the code is available at a password-protected NIST website.

To achieve this versatility and accuracy in a code that provides rapid response we employ schematic atomic structures, scaled hydrogenic cross-sections and read-in tables. It also employs the jj configuration averaged atomic states and oscillator strengths calculated using the Dirac-Hartree-Slater model[4] for spectrum synthesis.

Since the code uses an averaged model of atomic states, it predicts the level population distributions within the same hydrogenic configuration to be statistical and hence the state populations excited by the Δn=0 transition are overestimated in the coronal equilibrium. This leads to the small dielectronic recombination (DR) rate of M-shell (or N-shell) ions at low temperatures where Δn=0 channels are dominant in DR process. The radiative power loss rates from the bound-bound transitions are also affected when Δn=0 transitions dominate the rates at the coronal equilibrium.

Atomic data for FLYCHK are generated for all elements up to Z=79(Gold): oscillator strength, collisional excitation gaunt factors, photo-ionization cross-sections and autoionization rates with one exception of autoionization rates for ions with more than 60 electrons. For those ions, analytic formula is used to generate autoionization rates. FLYCHK code has never been validated against ions with more than 60 electrons and it is highly recommended for users to give us feedback on those results.

For ions with more than 3 electrons, STA <Super-configuration Transition Array> intensities are employed for a simple and fast calculation. Nevertheless, the K-shell lines such as K-α and K-β are found to give a reasonable result comparable to observations in the short-pulse laser experiments. The non-K-shell spectra give an overall shape of averaged spectral intensities. Users should take caution when applying these averaged spectra for plasma diagnostics.

[1]
**FLYCHK: Generalized population kinetics and spectral model for rapid spectroscopic analysis for all elements**, H.-K. Chung, M.H. Chen, W.L. Morgan, Y. Ralchenko and R.W. Lee, High Energy Density Physics, Volume 1, Issue 1, December 2005, Pages 3-12

[2]
**FLYCHK: an extension to the K-shell spectroscopy kinetics model FLY**,
H. -K. Chung, W. L. Morgan and R. W. Lee, Journal of Quantitative Spectroscopy and Radiative Transfer, Volume 81, November 2003, Pages 107-115

[3]
**A time-dependent model for plasma spectroscopy of K-shell emitters** R.W. Lee and J.T. Larsen, Journal of Quantitative Spectroscopy and Radiative Transfer, Volume 56, October 1996, Page 535-556

[4]
**Relativistic L-shell Auger and CosterKronig rates and fluorescence yields** M.H. Chen, E. Laiman, B. Casemann, M. Aoyagi and H. Mark, Phys. Rev. A 19 (1979), p. 2253