Aerodynamic focusing of heavy molecules in seeded supersonic jets

Journal Article · Tue Aug 15 00:00:00 EDT 1989 · J. Chem. Phys.; (United States)

DOI:https://doi.org/10.1063/1.456969· OSTI ID:5976183

Rosell-Llompart, J

The phenomenon of aerodynamic enrichment of heavy molecules seeded in supersonic free jets has been known since 1955. But its systematic exploitation in the generation of intensely focused molecular beams has been prevented by the lack of a quantitative and realistic explanation of the observed facts. Here, the aerodynamic focusing of CBr/sub 4/, W(CO)/sub 6/, and C/sub 2/Cl/sub 6/ molecules seeded in jets of He or H/sub 2/ is studied experimentally, and found to be most singular under conditions similar to those known to produce sharply focused beams of microscopic spheres suspended in air jets. The gas mixture expands through thin-plate orifice into a vacuum chamber, forming a supersonic free jet. The spacial distribution of the heavy molecules in the jet is measured at varying distances /ital L/ to the nozzle by scanning a thermocouple probe across a jet diameter. The probe is sufficiently small to interfere negligibly with the flow. The increment DV in the thermocouple voltage resulting from seeding the heavy gas on a given flow of He or H/sub 2/ is seen to be a sensitive indicator of the local concentration of seed molecules in the jet. The following behavior is observed in terms of the same Stokes number or inertia parameter /ital S/ that governs the simpler and better understood phenomenon of aerosol focusing. Below /ital S/=0.4 for H/sub 2/ and /ital S/=0.2 for He, heavy molecule and aerosol beam widths are practically identical, and the boundary of the jet of heavy molecules is rather sharp. At higher values of /ital S/, aerosol beams show further reductions

• Research Organization: Yale University, Department of Mechanical Engineering, New Haven, Connecticut 06520(US)
• OSTI ID: 5976183
• Journal Information: J. Chem. Phys.; (United States), Vol. 91:4
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
MOLECULAR BEAMS
FOCUSING
SUPERSONIC FLOW
AERODYNAMICS
BROMINATED ALIPHATIC HYDROCARBONS
CARBONYLS
CHLORINATED ALIPHATIC HYDROCARBONS
HELIUM
HYDROGEN
JETS
SPATIAL DISTRIBUTION
TUNGSTEN COMPOUNDS
BEAMS
DISTRIBUTION
ELEMENTS
FLUID FLOW
FLUID MECHANICS
FLUIDS
GASES
HALOGENATED ALIPHATIC HYDROCARBONS
MECHANICS
NONMETALS
ORGANIC BROMINE COMPOUNDS
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
RARE GASES
REFRACTORY METAL COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
640301* - Atomic
Molecular & Chemical Physics- Beams & their Reactions