Richard Clark wrote:
"The week is up and your (Art`s) search reveals you have gone off into
the ditch."

Look for the answer to how electrons escape a material on page 172 of
Terman`s 1955 opus. On page 173 Terman writes:
"It can be considered as an evaporation of electrons in which the energy
the electron must give up in escaping corresponds to the latent heat of
vaporization of the liquid."

Best regards, Richard Harrison, KB5WZI