Progress in overexpanded supersonic jets and skimmed molecular beams in free-jet zones of silence

Pulsed Supersonic Beams from High Pressure Source: Simulation Results and Experimental Measurements

“…Both cone nozzle and parabolic nozzle show a slower expansion rate resulting in higher beam number density (i.e., beam intensity) at a given distance from the nozzle. This slower expansion results in a many more collisions before the beam density becomes too low (the so called sudden freeze model [5,[31][32][33][34][35][36]), enabling more efficient cooling due to two-body collisions, as well as encouraging cluster growth via threebody collisions. One can conclude from these simulations that a conical or parabolic nozzle is much better than a sonic nozzle for obtaining high on-axis beam intensities.…”

Raman spectroscopy of supersonic jets of CO2: Density, condensation, and translational, rotational, and vibrational temperatures

“…This zone of silence approaches the ideal conditions of a perfect vacuum. 62 The low pressure chamber of 42ϫ42ϫ30 cm 3 , manufactured in aluminum, is connected to a vacuum system consisting of a rotary pump of 70 m 3 /h plus a Roots pump of 400 m 3 /h. For the continuous jet of higher flow rate, generated at a nominal stagnation pressure P 0 I ϭ203 kPa, this system is capable of maintaining the residual pressure below 0.4 hPa for hours.…”

Fast metastable hydrogen atoms from H2molecules: twin atoms

“…1) is equivalent to the classical one [29] for timeof-flight (TOF) studies of H(2s) produced by electron impact on H 2 , i.e., a hydrogen jet crossing at right angles with an electron beam. To reduce the spread of the velocity distribution of the hydrogen molecules, as well as to use well-defined initial molecular states and have sufficient target density, the hydrogen beam is produced by a Campargue-type supersonic jet source [30]. In the chamber where the collisions with the electrons take place, the pressure is maintained in the range 5 × 10 −7 to 1.2 × 10 −6 torr by a 2000 l/s diffusion pump.…”