The goal of the procedure is to obtain line fluxes. This is done most accurately when wavelengths and line widths are carefully chosen. Since this is not always possible, each of these two parameters can be optimized by iteration from given start values. With switches the iteration of ( ilamit) and the iteration of FWHM ( isigit) can be activated. When modeling multiplets, the distance between the individual lines is often well known and only the absolute position of the template of lines is to be iterated. Especially when the multiplet contains weak lines, it can be desirable to treat the multiplet as a unit and iterating only the position of the multiplet ( idlam=1). The line width FWHM can be iterated as the same value for all lines by setting idsig to 1. This is useful when the line width is determined by the instrument and is identical for all lines.
The parameter iord is a factor with which all wavelength values are multiplied before starting the fitting tool. This is useful when systematic shifts of the spectrum are expected, e.g., higher dispersion orders or reddening. These parameters must appear in the parameter file by putting ilamit, idlam, iord, and idsig on the same line and putting isigit on the next line.