Molecular Beams Formed by Arrays of 3–40 μ Diameter Tubes

摘要

The results of an experimental investigation of molecular beams formed by a closely packed array of glass tubes of uniform diameter are presented. The sets of tubes used (which are commercially available) ranged in diameter from 3 to 40 μ with length-to-diameter ratios of 12 to 100, and were driven by pressures extending from 0.025 to 15 Torr. The experimentally determined functional variations for flux density, on-axis intensity, and beam half-width (conditions L≥λ and a «L) are: Q/A= 3 2 ( 2 /3π)(ν¯/σ2)(L/λ)(Є/L)(a/L),Ic/A=(1/8π 3 2 )(ν¯/σ2)(L/λ) 1 2 (Є/L)(a/a0) 1 3 ,θ 1 2 =(4/√π)(L/λ) 1 2 (a/L).L is the length of the tubes, a is the tube radius, and Є is the percent transparency of the area A of the array. It is found experimentally that the flux is approximately ⅔ of that predicted theoretically, the beam width is twice that predicted theoretically, and the prediction for center line intensity is modified by (a/a.)⅓ The dependence of the beam intensity on the tube radius is attributed to self-scattering due to the dense packing of many tubes.