We have mentioned the natural broadening giving a Lorentzian profile, the thermal broadening introducing a Gaussian profile, and the general intermediate profiles as the most common cases. A consequence is that the Voigt profile, that is the convolution of Gaussian and Lorentzian functions, is generally used to simulate the intermediate case 1 . "Alternatively, [we can] suppose that the line is scanned by a spectrophotometer with a Gaussian sensitivity function" . Then, in this experimental framework, we have the convolution of the line with the instrumental function profile. Let us remember that "the general expression that takes account of all the instrumentally induced distortion of the true band shape can be called the instrument function" . It is also known as the "instrumental transfer function" .