Abstract: | This paper computes the rotational energy levels of the HCO transition, especially, the higher values of the rotational quantum numbers NKa Kc and Ka, with the rotational constants which are obtained via B3LYP method with 6-311G basis set, and the results show that the calculated frequencies using the computed vibration--rotation energy levels are in reasonable agreement with the data from the experiment. Meanwhile, the line intensities of HCO are first reported, the results are of significance for the studying HCO. |