Populations of rotational levels of molecules in clouds with large red shift

The influence of the field of the microwave background on the populations of the rotational levels of CO molecules in molecular clouds of galaxies with large red shifts is studied. The regions of kinetic temperatures and gas concentrations typical of molecular clouds of our Galaxy, 102 ≤ N/sub H2/ (cm-3) ≤ 106 and 20 ≤ T/sub k/(K) ≤ 100, are considered. The influence of the field of the microwave background is investigated in the interval of red shifts 1 ≤ z ≤ 5. It is shown that this influence is important already when N/sub H2/ < 104 cm-3 and is dominant for N/sub H2/ = 102-103 cm-3