The high field enhancement of photoemission from Na2KSb photocathodes

We measured the enhancement of photoemission by the application of a high electric field to the surface of Na2KSb photocathodes which were stimulated by ultrashort laser pulses (wavelength 1.06 μm or 0.53 μm, pulse duration 50 ps). The gain in photoyield exceeded 5 at a field of 2.7 × 107V/m, and there were steps in the curve of the gain in photoyield versus the applied electric field.