  Experimental measurements of the extraction efficiency f of the UV-induced
photoelectrons emitted from a CsI photocathode into gas mixtures of Ne with
CH4, CF4, CO2 and N2 are presented; they are compared with model-simulation
results. Backscattering of low- energy photoelectrons emitted into noble gas is
significantly reduced by the admixture of molecular gases, with direct impact
on the effective quantum efficiency. Data are provided on the dependence of f
on the type and concentration of the molecular gas in the mixtures and on the
electric field.
