Pulse supersonic outflow of Ar, SiH4 and Ar + SiH4 gas mixture (where monosilane is a small admixture) was studied experimentally by the method of molecular beam mass-spectrometry. Using argon as an example we have shown that condensation processes at the quasi-stationary region of a pulse flow and within a stationary jet are similar. In the flows of pure gases clusters of argon and silane (hydrogenated silicon) and in the mixture argon - silane complexes were registered. The dependencies of the intensities of monomer and cluster ions on stagnation pressure were investigated. It was shown that in the mixture jet at low stagnation pressures the condensation process with the formation of monosilane clusters takes place and at high pressures mixed argon-silane complexes are formed. The parameters of flow transition into the regime of developed condensation were determined for pure gases and their mixture.