Accession Number : AD0711078

Title :   A CRITICAL EVALUATION OF THE METASTABLE TIME-OF-FLIGHT TECHNIQUE FOR OBTAINING MOLECULAR VELOCITY DISTRIBUTIONS,

Corporate Author : TORONTO UNIV (ONTARIO) INST FOR AEROSPACE STUDIES

Personal Author(s) : Locke,J. W.

Report Date : DEC 1969

Pagination or Media Count : 93

Abstract : The paper describes how a fundamentally new method for measuring the distribution of molecular velocities, the Metastable Time-of-Flight (MTF) method, was taken from the concept stage to a point where it may be used with a considerable degree of confidence by workers in such fields as rarefied gas dynamics, surface physics, and gas-phase chemistry. The sensitivity of the MTF method has been measured in absolute terms and as a function of impact voltage for ten common gases - He, Ne, Ar, Kr, Xe, N2, H2, CO and CO2. On the basis of the cross section values obtained, the MTF method might seem to be less sensitive than methods employing rotating mechanical systems with ionization detectors. However, other considerations such as the extremely narrow entrance slits required to achieve good speed resolution by mechanical methods mean that the two approaches are comparable in sensitivity in practice. It is shown that MTF does work well in the case of the first seven of these gases with the detector used and with a different detector would likely work with O2 and CO. There does not seem to be any hope of using MTF with CO2 as it lacks a suitable state. All second order effects associated with this method have been investigated and shown to be generally small. The hardware requirements for implementing the MTF technique are discussed at length including the design of the electronic instrumentation required. The result of this work is the existence of a new, well-characterized method for velocity analysis. (Author)

Descriptors :   (*GAS FLOW, VELOCITY), (*MASS SPECTROSCOPY, GAS FLOW), SPECTRUM ANALYZERS, DIATOMIC MOLECULES, DESIGN, CANADA

Subject Categories : Test Facilities, Equipment and Methods
      Atomic and Molecular Physics and Spectroscopy

Distribution Statement : APPROVED FOR PUBLIC RELEASE