The molecular spectroscopic methods of CBR-temperature measurement in epochs with large redshifts

Investigations of the properties of the matter in earlier cosmological epochs by using methods of studying of the interstellar gas clouds at large cosmological distances by analyzing QSO absorption line systems is reviewed. It is suggested that it is also possible to detect the absorption lines of the most abundant molecules such as CO, OH, CH, and CN in QSO spectra. Focus is placed on CH-rotational transitions and the advantages of CH over CI in the context of the problem. It is concluded that with the progress in the millimeter-range radio astronomy, the detection of CH lines in the QSO spectra will make it possible not only to obtain detail characteristics of absorbing clouds but also to measure the background temperature of the earlier cosmological epochs. (V.T.)