Abstract: This code contains several simple radiative transfer models used for fitting the blue-asymmetric spectral line signature often found in infalling molecular cloud cores. It attempts to provide a direct measure of several physical parameters of the infalling core, including infall velocity, excitation temperature, and line of site optical depth. The code includes 6 radiative transfer models, however the conclusion of the associated paper is that the 5 parameter "hill" model (hill5) is most likely the best match to the physical excitation conditions of real infalling Bonnor-Ebert type clouds.
Credit: Christopher H. De Vries, Philip C. Myers; please include a reference to the De Vries & Myers (2005) paper in papers
The code is introduced in the following paper, which describes it in detail: http://adsabs.harvard.edu/abs/2005ApJ...620..800D