Ionization chambers for the vacuum ultra-violet

The characteristics of a number of selective ultra-violet ion chambers of the Friedman type are described. Ethyl chloride, ethyl bromide, carbon disulphide, acetone, ethyl iodide, nitric oxide, benzene, toluene, p -xylene and mesitylene have been used as filling gases to limit the response of the chambers on the long wavelength side. Windows of lithium fluoride, calcium fluoride, barium fluoride and sapphire provide the short wavelength cut-offs. The spectral response curves and quantum efficiencies of these chambers have been determined and photo-absorption coefficients have been measured for a number of the filling gases.