Physics Letters AZero-phonon lines and phonon-sidebands in the 4f7 6s2 → 4f6 5d6s2 absorption spectrum of Eu atoms isolated in an argon matrixM. Jakob, Hans Micklitz, K. LuchnerPublished May 1, 1976• 12 citationsPublisherDOI10.1016/0375-9601(76)90457-6