Lineshape in a Laval Molecular Beam and Pressure Broadening of N2O Transition Lines

We have measured the absorption profile of N2O transitions belonging to the v2 vibrational band at 589cm-1 in order to characterize the gas flow in a pulsed Laval molecular beam. It is found that the shape of the transition is almost Lorentzian near the nozzle exit while it clearly approaches a Gaussian profile far away from the nozzle throat. After measuring the spectral profiles for the same transition in a cell at different pressures, we were able to quantify the molecular density along the Laval stream. We have also measured the pressure-broadening parameters of few transitions of the v2 band.