Physical processes in the interstellar matter determining parameters of radio recombination lines in meter and decameter ranges

Problems connected with the interpretation of meter decameter carbon radiolines are reviewed. The lines are formed inside clumps of molecular clouds in layers with a column density of 6 x 10 to the 21st/sq cm. These clumps are very typical structures. The distribution of physical parameters inside the clumps is poorly known. The most difficult and important question is the penetration of subcosmic rays into the clumps. Long-wave radio recombination lines can probably be used for the analysis of the distribution of subcosmic rays inside molecular clouds.