Testing the validity of supersonic molecular beam modeling in the high-throughput range using an Even-Lavie valve

Supersonic molecular beams are used in several scientific fields ranging from surface science to the spectroscopy of molecules, nanoparticles, and even viruses. It is therefore of interest to understand the fundamental properties of the expansion and resulting beam. Here, we present a study of the change in the most probable velocity with reservoir pressure, using a so-called Even-Lavie pulsed source with a 200-µm-diam nozzle. Experiments were carried out in the throughput range p0d=400–2000 mbar cm, where p0 is the reservoir stagnation pressure and d is the nozzle diameter. Experiments were done on both neutral and metastable helium beams. A two-detector measurement setup was used to account for the valve opening delay. The measurements are modeled with theory which has hitherto only been applied to a p0d regime up to 190 mbar cm, showing good agreement.