A set of thin GaAs p-type negative electron affinity (NEA) photocathodes have been used to measure the yield of photoemitted electrons at high intensity excitation. The active layer thickness is 100 nm and the p-type doping ranges from 5×1018 to 5×1019 cm−3 for a set of four samples. The results show that the surface escape probability is a linear function of the NEA energy. The surface photovo...

The results of density functional theory based calculations on Ga3O, Ga3O2, Ga3O3, Ga2O3, and GaO3 clusters are reported here. A preference for planar arrangement of the constituent atoms maximizing the ionic interactions is found in the ground state of the clusters considered. The sequential oxidation of the metal-excess clusters increases the binding energy, but the sequential removal of a me...

The 351 nm photoelectron spectra of OH~NH3!n n51,2 and the deuterated analogs exhibit two broad peaks. Ab initio calculations of the anion and neutral potential-energy surfaces have been carried out using an MP2 ~second-order Mo”ller–Plesset!/6-3111G** basis set. The geometries, frequencies, and energetics from these calculations aid in the interpretation of the experimental results. An estimat...

Polarized electron beams are now in routine use in particle accelerators for nuclear and high energy physics experiments. These beams are presently produced by dc-biased photoelectron sources combined with rf chopping and bunching systems with inherently high transverse emittances. Low emittances can be produced with an rf gun, but the vacuum environment has until now been considered too harsh ...

Injecting charge carriers into the mobile bands of an inorganic oxide insulator (for example, SiO2, HfO2) is a highly complicated task, or even impossible without external energy sources such as photons. This is because oxide insulators exhibit very low electron affinity and high ionization energy levels. Here we show that a ZnO layer acting as a cathode buffer layer permits direct electron inj...

The potential energy surface of the Fe dimer is investigated on the basis of density functional theory in the generalized gradient approximation (GGA). Electron correlation effects are taken into account explicitly within the GGA+U approach. We find a value of 2.20 eV for the Coulomb repulsion parameter U to describe the Fe dimer best, yielding a 9 Sigma(g)- ground state with an interatomic sep...

The photoelectron spectra of FeO and FeO2 2 are obtained at 3.49 eV photon energy. Transitions to the ground state ~D! and three low-lying excited states ~S, S, and D! of FeO are observed. The two low-spin excited states found at 6770 and 8310 cm above the ground state, respectively, have not been observed before. The two S states, characteristic of detachment of a nonbonding electron from the ...

conclusions using the maximum dose depth from pdd curves and the inverse square law, the required ssdeff to calculate the dose distribution of the electron beam can be calculated. objectives the aim of this study was to determine the effective source-surface distance (ssdeff) of an electron linear accelerator (linac), and its dependence on energy and depth. materials and methods a varian linac ...