Photoemission study of the electronic structure of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">C</mml:mi></mml:mrow><mml:mrow><mml:mn>60</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">K</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant="italic">x</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">C</mml:mi></mml:mrow><mml:mrow><mml:mn>60</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

High-resolution photoemission studies have been performed on undoped and K-doped ${\mathrm{C}}_{60}$ films. In the undoped material, temperature-dependent measurements showed no significant change of the valence-band electronic structure on crossing the structural phase transitions at 90 K and 249 K. Studies of ${\mathrm{K}}_{\mathit{x}}$${\mathrm{C}}_{60}$ conducted with a variety of photon energies and doping levels show that ${\mathrm{K}}_{3}$${\mathrm{C}}_{60}$ is a metal, with a sharp Fermi edge situated at the maximum of the occupied part of the lowest unoccupied molecular orbital-or LUMO-derived bands. The density of states observed at the Fermi level shows a maximum at x=3, indicating that there is no pseudogap at the Fermi level of ${\mathrm{K}}_{3}$${\mathrm{C}}_{60}$. The spectral weight of the occupied LUMO-derived states with respect to those of the highest occupied molecular orbital (HOMO) is found to be photon-energy dependent. A surface K content greater than x=6 can be achieved and is found to be correlated with the presence of a potassium oxide overlayer. The results are discussed with reference to the need for absolute, accurate determination of the surface K content of the samples studied by photoemission.