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The kinetic energy distributions of photo-electrons emitted from goldsurfaces under illumination by UV-light close to the threshold are measured andanalyzed. Samples are prepared as chemically clean through Ar-Ion sputteringand then exposed to atmosphere for variable durations before Quantum Yieldmeasurements are performed after evacuation. During measurements the biasvoltage applied to the sample is varied and the resulting emission currentmeasured. Taking the derivative of the current-voltage curve yields the energydistribution which is found to closely resemble the distribution of totalenergies derived by DuBridge for emission from a free electron gas. Weinvestigate the dependence of distribution shape and width on electrodegeometry and contaminant substances adsorbed from the atmosphere, in particularto water and hydro-carbons. Emission efficiency increases initially during airexposure before diminishing to zero on a timescale of several hours, whilstsubsequent annealing of the sample restores emissivity. A model fit function,in good quantitative agreement with the measured data, is introduced whichaccounts for the experiment-specific electrode geometry and an energy dependenttransmission coefficient. The impact of large patch potential fields fromcontact potential drops between sample and sample holder is investigated. Thetotal quantum yield is split into bulk and surface contributions which aretested for their sensitivity to light incidence angle and polarization. Ourresults are directly applicable to model parameters for the contact-freedischarge system onboard the LISA Pathfinder spacecraft.

Energy distribution and quantum yield for photoemission from air-contaminated gold surfaces under UV illumination close to the threshold