Changes

Our proposed explanation involves ions ejected with some constant probability upon the incidence of accelerated electrons. This positive ion is accelerated in the opposite direction to the path of the electron, back to the bialkali layer. Collision with this layer generates more electrons, which are accelerated and multiplied just as the first. In this model, the lone peak of a single photo-electron (of width ''σ₁'') is joined by another centered about some value ''p'' (of width ''σ₂'') representing the mean number of electrons generated by the ion's collision with the bialkali layer. The ratio of integrals of these peaks (''α'') represents the probability of the ion's ejection for every primary photo-electron. Increasing input to ''m'' photo-electrons essentially means a convolution of this spectrum with itself ''m''-times.  

Our proposed explanation involves ions ejected with some constant probability upon the incidence of accelerated electrons. This positive ion is accelerated in the opposite direction to the path of the electron, back to the bialkali layer. Collision with this layer generates more electrons, which are accelerated and multiplied just as the first. In this model, the lone peak of a single photo-electron (of width ''σ₁'') is joined by another centered about some value ''p'' (of width ''σ₂'') representing the mean number of electrons generated by the ion's collision with the bialkali layer. The ratio of integrals of these peaks (''α'') represents the probability of the ion's ejection for every primary photo-electron. Increasing input to ''m'' photo-electrons essentially means a convolution of this spectrum with itself ''m''-times.  

A fit of this model to the data was attempted with all parameters remaining free except the gain and the position in the spectrum corresponding to zero photo-electrons.

A fit of this model to the data was attempted, assuming the initial peaks are Gaussians, with all parameters remaining free except the gain and the position in the spectrum corresponding to zero photo-electrons. It turned out, however, that the model could not account for the long right-hand tail of the distribution, seen in the above figure. Evidently, the naive assumption that the secondary electron emission spectrum generated by the ion is inaccurate. A crude introduction of asymmetry in the peak of secondaries was introduced by another Gaussian with its location (''r''), normalization (''β'') and width (''σ₃'') as another set of free parameters.