The theoretical and experimental study of the spectral and energy characteristics of radiation of the pulsed photoinitiated HF/DF-laser operating on the chain chemical process in the gas mixture F2:(H2+D2):02:He3 : 1 :0.3 :6.7 of atmospheric pressure depending on the relation between the initial concentrations H2 and D2 and the oscillation threshold is carried out. The optimum requirements for a simultaneous oscillation on molecules HF and DF in a wide spectral range from 2.7 up to 4.8 pm are determined in experiment and also by numerical modeling.