There are abundant emission and absorption lines superimposed on the continuum spectrum of the solar atmosphere at different levels. The chemical composition and physical state of the solar atmosphere can be probed by the inversion of the profiles of the measured spectral lines. Due to its low density and large temperature difference, it is hard to establish thermal dynamic equilibrium in the chromosphere and transition regions of the sun. In this paper, the departure from thermodynamic equilibrium in the middle and lower atmosphere of the sun is investigated according to the well-defined relative departure factor and the corresponding calculation. We invert the spectral lines formed from chromosphere and transition regions at different heights during a total solar eclipse observation to obtain the line parameters, such as continuum source function, line source function, Doppler width and thus the equivalent kinetic temperature, and then the relative departure factor is calculated. Then, we reconstruct the two-dimensional distribution maps of radiative intensity, equivalent kinetic temperature and relative departure factor according to the alignment of optical fiber array of the integrated field unit (IFU) used by FASOT-1A telescope. The results show that there is a certain correlation between the distribution of temperature and relative departure factor, but no evident correlation with the distribution of radiation intensity. The spatial distributions of both effective temperature and departure from thermal equilibrium of the two lines have very different patterns, showing complicated structures. This provides a new perspective for us to further understand the physics of the middle and lower atmosphere of the Sun.
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