• Detection of modulated molecular beams with electron bombardment detectors

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      https://www.ias.ac.in/article/fulltext/pram/011/03/0307-0311

    • Keywords

       

      Molecular beams; neutral beam detection; molecular beam scattering; collision cross-sections

    • Abstract

       

      By means of refinements in the modulated molecular beam technique the signal-to-noise ratio can be greatly improved, and differential cross-sections, for collision of molecuies of the same species, can be measured. This was accomplished by combining beam modulation and phase sensitive detection with very sharp turning on the front end of the lock-in-amplifier and long integration times on the output. In addition, the signal-to-noise ratio of the Ar-Ar system as a function of integration time was investigated using two different types of electron bombardment detectors an Aberth ion-source and a quadrupole mass filter. With an integration time of 40 min the estimated upper limit to the signal-to-noise ratio is 1500 to 1 for the Aberth ion-source. Using quadrupole mass filter with an integration time of 60 min the estimated upper limit to the signal-to-noise ratio is 5 × 104 to 1. For chemical kinetics studies this ratio may be two orders of magnitude higher.

    • Author Affiliations

       

      P K Chakraborti1

      1. Bhabha Atomic Research Centre, Bombay - 400 085
    • Dates

       
  • Pramana – Journal of Physics | News

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