# Spectral Line Shapes Software

The main goal of Spectral Line Shapes (SLS) is to develop easy-to-learn, easy-to-use software tools for government, commercial and academic research and development. The SLS software tools are also helpful for graduate and undergraduate research and education. The SLS software features a graphical user interface to simplify the selection of observed atomic transitions and their belonging atomic data and to visualize the dependence of the predicted spectral line profiles for selected plasma parameters. All software-supported output files and figures can be imported into the reporting documents with a simple 'copy-paste' operation. The spreadsheet files are saved in two standard file formats: Microsoft Excel and ASCII. The SLS software runs natively on Windows and supports multi-core CPU processing.

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The SLS tools enable researchers and engineers to conduct theoretical and computational studies of the laboratory and astrophysical plasmas, create new or improve existing spectroscopy-based plasma diagnostics methods for characterization and optimization of laboratory and industrial plasma applications. Typical applications are the industrial plasma processes, laboratory plasma sources created by electric discharge (zeta-pinch, theta-pinch), microwaves (Microwave Induced Plasma / MIP), and lasers (Laser-Induced Plasma / LIP, Laser-Induced Breakdown Spectroscopy / LIBS). The SLS tools can be applied to atoms and atomic ions found in a laboratory, naturally occurring, and astrophysical plasmas. The spectral line profiles originated from atomic transitions in plasma can be simultaneously modeled by the SLS tools for neutral, single, and multiple charged atomic emitters as a function of the plasma parameters. The computed spectral line parameters are also important parameters for the plasma radiation codes.

The SLS computational algorithms for major spectral line broadening and shifting mechanisms are vectorized and parallelized for fast execution on multi-core CPUs. They address Natural, Doppler, Van der Waals, Resonant, and Stark spectral-line broadening and shifting.

Computationally most demanding calculations of the Stark spectral line parameters are balanced between the accuracy and the computing time by the implementation of several theoretical approaches in the SLS: Semi-Empirical Formula (SE), Modified Semi-Empirical Formula (MSE), Simplified Semi-Classical Formula of Griem (SSC) and Semi-Classical Method of Griem (SCG). The SE, MSE, and SSC approaches are optimized vs. the computing time, while the SCG method prioritizes the solution accuracy over the computing time.

The SLS software enables the user to compute the exact solution of the Plasma Composition in Local Thermodynamic Equilibrium (LTE). This tool estimates the particle densities of all plasma constituents for pairs of the input plasma parameters: (Ne, T), (Ne, P), and (P, T), where Ne, P, and T are the electron density, pressure, and temperature in plasma, respectively. The LTE Plasma Composition Solver is a helpful tool for the design and optimization of plasma sources.

The transition probability calculator for the electric and magnetic dipole and quadrupole transitions is part of the SLS package. The atomic transition probabilities can be calculated between the electronic configurations of the same or different coupling schemes. The coupling schemes include LS, LK, J1K, J1j, and jj couplings. Computational routines for the Coefficients of Fractional Parentage (CFP) are integrated into the transition probability calculator.

The SLS tools use the atomic data from the National Institute of Standards and Technology (NIST) Atomic Spectra Database (ASD). The initial SLS configuration requires the download of the ASD to the local computer. The ASD is not distributed with the SLS package, as it belongs to the U.S. Government. The SLS user can update the local copy of ASD by downloading its current version from the NIST server at any time. Consequently, the SLS calculated spectral line profiles and plasma composition parameters would compute with NIST's most recent atomic data.

For more information about the SLS software, please request the SLS demo software and the User Manual.

###### Examples

Example 1: The spectral line of Ar I 1048.2199 A 3s2.3p6 1S - 3s2.3p5.(2Po<1/2>).4s 2[1/2]o, calculated in Semi-Classical impact approximation of Griem (SCG). The perturbing levels of the upper level of the transition have J1K rather than LS coupling. The Debye shielding correction on the line width and shift reveals the significant influence to the line shift of Ar I 1048.2199 A. The SLS calculates the correction to Debye shielding for the spectral line profiles originated from neutral atoms.

Example 2: The width and shift of Mg II 2796.3518 A calculated in the Semiclassical Impact Approximation of Griem (SCG). The temperature dependences of spectral linewidth and shift are normalized to the plasma electron density of 1E17 cm^-3.

Example 3: The width and shift of Ar VII 3s.4s 1S - 3s.4p 1Po 2445.7652 A, calculated in Modified Semi-Empirical approximation (MSE). The temperature dependences of spectral linewidth and shift are normalized to the plasma electron density of 1E17 cm^-3.

Example 4: Calculated Mg II 2796.3518 A spectral line width and shift parameters vs. the plasma temperature, for several line broadening and shifting mechanisms: Doppler, resonant, Van der Waals and natural. The Doppler shift is calculated for predefined emitter velocity (equal to zero in this example).

Example 5: The LTE Plasma Solver solution for inductively coupled Argon plasma (ICP) mixed with CF4 at 6000 K plasma temperature and 1E15 cm^-3. The concentration of singly charged Fluorine ions is predicted to be lower than the concentrations of singly charged Argon and Carbon ions.

Example 6: LTE Plasma Solver solution for pure Uranium plasma. U XXVII and U XXVIII ions are dominant emitters at T=1,000,000 K plasma temperature and Ne=1E20 cm^-3 electron density. Low Uranium ion densities are not listed, but rather displayed as the numerical error of LTE solution.

Example 7: Comparison of the line strengths calculated by the enhanced Bates-Damgaard (BD) method used in the SLS vs. NIST ASD tabulated values for the transitions between the perturbing levels of the upper and lower level in B III 1s2.3s 2S 1/2 - 1s2.3p 2P0 3/2 7839.4583 A.