  An inverse P-Cygni profile of H13CO+ (1-0) in G31.41+0.31 was recently
observed, which indicates the presence of an infalling gas envelope. Also, an
outflow tracer, SiO, was observed. Here, exclusive radiative transfer modelings
have been implemented to generate synthetic spectra of some key species (H13
CO+, HCN, SiO, NH3, CH3 CN, CH3OH, CH3SH, and CH3NCO) and extract the physical
features to infer the excitation conditions of the surroundings where they
observed. The gas envelope is assumed to be accreting in a spherically
symmetric system towards the central hot core region. Our principal intention
was to reproduce the observed line profiles toward G31.41+0.31 and extract
various physical parameters. The LTE calculation with CASSIS and non-LTE
analysis with the RATRAN radiative transfer codes are considered for the
modeling purpose. The best-fitted line parameters are derived, which represents
the prevailing physical condition of the gas envelope. Our results suggest that
an infalling gas could explain the observed line profiles of all the species
mentioned above except SiO. An additional outflow component is required to
confer the SiO line profile. Additionally, an astrochemical model is
implemented to explain the observed abundancests various species in this
source.
