X-Ray Transition Energies Database by National Institute of Standards and Technology

Primary evaluated transition-energy database. The copper experimental $K{L}_3$ entry is near $8047.8227\mathrm{eV}$ and can be converted into the Cu K${\alpha }_1$ wavelength with $hc/E$. physics.nist.gov/cgi-bin/XrayTrans/search.pl?element=Cu&lower=&units=eV&upper=