Total π-meson photoproduction cross section for lithium and beryllium

Abstract

The total photon absorption cross section for natural Li and Be have been measured up to 220 MeV photon energy. The rise of the cross section above an ‘apparent’ threshold of about 170 MeV indicates the main onset of π-meson photoproduction. The cross section at 200 MeV is larger for Li than for Be (1.25 mb and 0.8 mb, respectively), and the integrated cross section from the apparent π-production threshold to 220 MeV constitutes a sizeable fraction of the classical dipole sum (34% and 24%, respectively).