Location of Optical Transitions ink→space from Angular Photoemission Measurements on W

The energy and emission angle of electrons photoemitted from the (110) and (111) surfaces of W have been measured for photon energies between 7.7 and 10.7 eV. For prominent transitions, the component of internal $\overrightarrow{\mathrm{k}}$ vector tangential to the surface was obtained from angular measurements on each of the two surfaces. The two components of $\overrightarrow{\mathrm{k}}$ were used to determine the internal $\overrightarrow{\mathrm{k}}$ vector of prominent transitions occurring in the plane defined by the $〈110〉$ and $〈111〉$ axes.