The Rayleigh scattering method is widely adopted in measuring cluster size.In general,it is considered that the intensity of scattering corresponds to the cluster size directly.However,this paper deduces that the intensity is not only related to cluster size,but also to gas density and binding probability.It suggests that gas density should be taken into account in analyzing the measurement results of Rayleigh scattering method.Furthermore,the method is applied in measuring the size distribution of argon cluster along the axis of nozzle.It is found that the cluster size doesn't vary linearly along the nozzle axis,whereas it reaches maximum at a certain position which depends on some parameters including the background pressure.

The Rayleigh scattering and Mach-Zehnder interferometry are employed to investigate the properties of argon and krypton clusters respectively.By comparing the size and density of the two kinds of clusters in detail,the factors of cluster formation are discussed.Varying the delay time between probe laser and nozzle valve,the temporal evolution of size and density is obtained,the density spatial distribution along nozzle axis with the background pressure from 1.2 MPa to 6.0 MPa is measured.Both size and density of the argon and krypton clusters reach max and the system is stable from 3 ms to 25 ms.In addition,the density increases linearly with background pressure,and decreases with the distance away from the nozzle throat.