The Physical Nature of H₂CO Clouds in Dark Clouds, B5 and L1535

By fitting the data of the H₂CO 2 mm (140 GHz and 150 GHz), 2cm (1.45GHz)and, 6 cm (4.3GHz)lines we observed in the dark clouds, B5 and L1535, to the values calculated by the hydrostatic equitlibrium polyt ropic model developed by B.E.Turner, we derived the total density, the fractional abundance of H₂CO, the column densities of H₂and CO, the line temperature arising from various transitions, the line temperature ratio between different transitions, and visual extinction at the cores of the clouds.We also examined the effect of external UV field intensity on the line temperatures and their ratios.