This paper presents detailed calculations of the energy deposited by energetic photons in spherical, uncharged, interstellar dust particles. The interaction of the photons in the solid creates fast electrons from photoionizations, Auger transitions, or Compton scattering, which deposit a fraction of their energy in the dust. Fluorescent transitions following a K-shell photoionization in iron also contribute to the heating. The efficiency of the dust heating depends on the initial photon energy and on the grain size and composition. Calculations are performed for carbon and silicate particles of radius 50 Angstrom to 1 mu m, irradiated by photons with energies between 10 eV, which is about equal to the threshold for the ejection of photoelectrons, and 1 MeV, beyond which pair production dominates the photon interaction in the solid. Our studies present a consistent treatment of the partitioning of the energy of photons that interact in the dust into an absorbed fraction and a fraction that is carried away by ejected electrons. The results are presented in tables listing the energy deposited in a dust particle, E(dep), as a function of incident photon energy, E(gamma), and plots depicting the energy carried away by the ejected electrons as a function of E(gamma). The results of this work are useful for calculating dust temperature fluctuations and equilibrium dust temperatures in astrophysical environments in which the dust is exposed to hard ultraviolet and X-ray emission and for calculating the photoelectric heating of clouds exposed to similarly hard radiation fields.
