Direct determination of lifetime and energy dispersion for the empty 1 conduction band of copper

We present an accurate determination of the energy dispersion (E vs k) and the first direct determination of the energy-dependent lifetime (E) of well-defined excited Bloch states in a crystal. Using angle-resolved photoemission for Cu(100), we find that the lifetime broadening increases from =1.2 eV (6 × 10-16 sec) to 1.8 eV (4 × 10-16 sec) for 1 conduction-band states ranging 10.5 to 13.5 eV above the Fermi level. The measured dispersion (2% accuracy) shows a reduced effective mass (m*m0=0.90-0.94) which is related to self-energy effects. © 1978 The American Physical Society.