Intensitätshysterese der Photoemission von Multialkalikathoden bei 77 °K

Abstract

In a preceding paper it was reported on the photoemission of multialkali photocathodes with temperatures of about 77 °K, where nonlinearities, discontinuities and hystereses of the emission current were observed when the wave length and the intensity of the light was varied. In the following a detailed account is given on measurements of hystereses with alternating light intensities. Furtherly the absorption of the photocathodes was measured, while the emission current was at a discontinuity with a jump of the current by a factor of two and more. The absorption was independent of the jumps. From this and from a detailed discussion of the intensity hystereses it can be concluded an independence of the effect of: a) the primary interaction of the light with the cathode, b) the conduction mechanism of electrons through the cathode (for then otherwise a band gap of 7.05 eV should follow), c) the potentialstep at the cathode surface. Observed quantum yields of 100% are not due to electron multiplication by the initial energy of the excited photoelectrons but seem to indicate an exciton mechanism and/or field effect, the latter being quite different from the Malter effect. The intensity at which the upward jump occurs increases by a factor of ten when the cathode temperature rises by 0.36 °K. This temperature sensitivity is interesting in application as radiation detector.