NKABS

The NKABS code is used to calculate the optical constants (complex refractive index) of thin films directly from the absorbance data in the infrared. It is written in the Python language, being more accurate and faster than previous methods in the literature. For solving the Kramers-Kronig relationship, we used Maclaurin's methodology. Unlike other codes, which found convergence in 30 to 40 iterations, the NKABS reach the convergence in just 4 or 5 iterations. Additionally, to evaluate the error, this code calculates the MAPE (Mean Absolute Percentage Error) and the chi-square χ2. The typical MAPE error obtained using NKABS is less than 1 x 10^-3 %. The code is available online as well as the database obtained here. The NKABS can be also employed for the calculation refractive index of processed samples (by heating or radiation). Such data, as well as the refractive index of virgin samples, are needed as input in several astrophysical models that calculates the radiative transfer in dusty astrophysical environments such as protoplanetary disks and circumstellar environments as well dense molecular clouds. The first version of the code was developed during the PhD thesis of Will Robson in 2013.

The original paper can be obtained here (PDF).

The Figure below show the real and imaginary part of complex refractive index in the infrared of 4 ices in different mixtures (Rocha et al. 2017). The full database in ascii format available HERE.