The rotational temperature behaviour in adiabatic jet expansion of molecular nitrogen is investigated over a wide range of stagnation density and nozzle diameter values using coherent anti-Stokes Raman spectroscopy (CARS). Estimates of rotational collisional numbers are made for both (N2 + N2) and (N2 + Ar) systems. The aspect of cluster formation for both systems is also discussed.
PACS: 42.65
Supersonic free-expansion jets can be effectively used for solving a number of problems connected with lowtemperature and low-pressure spectroscopy, translational, rotational, and vibrational relaxation processes, cluster structure and condensation dynamics [1][2][3][4][5]. Detailed information (on the molecular level) about the processes in the flow can be obtained by several spectroscopic techniques, such as electron-beam diagnostics, laser-induced fluorescence, infrared absorption, and Raman scattering [6][7][8][9][10][11]. During recent years a number of coherent nonlinear scattering techniques for diagnostics of Raman-active transitions have been successfully used for temperature and density measurements [12][13][14][15][16][17], and for investigation of condensation processes in supersonic jets [18][19][20].
In this paper we report the results of an investigation of rotational temperature behaviour in adiabatic jet expansion of molecular nitrogen over a wide range of stagnation density and nozzle diameter values using coherent anti-Stokes Raman spectroscopy (CARS). Estimates of rotational collisional numbers are made for both (N2 + N2) and (N2 + Ar) systems. The aspect of cluster formation for both systems is also discussed.