Multiple Nuclear Disintegrations Induced by 100-Mev X-Rays

Multiple nuclear disintegrations have been observed in light and heavy nuclei irradiated with high energy x-rays generated by a 100-Mev betatron. 1500 photographs taken with a 12" cloud chamber filled with air have yielded 105 single protons of energies up to 9 Mev, 7 "flag" tracks showing a proton or alpha particle and a heavy recoil nucleus, and 3 four-particle "stars," in two of which one alpha-particle, two protons, and a recoil nucleus can be identified. At least one neutron must accompany the observed particles in each multiple track to satisfy the momentum conservation law. In one star, a particle which may be of intermediate mass is observed as one of the disintegration products. No recoil protons in hydrogen were observed in 150 photographs, indicating that fast neutrons are not present in sufficient intensity to cause the observed disintegrations. Identification of residual nuclei by measurement of the half-lives of radioactivity induced in irradiated samples has revealed many multiple disintegration processes. Strong activities were observed from ($\gamma ,p$) and ($\gamma ,2n$) reactions, moderately strong activities from ($\gamma ,pn$), ($\gamma ,2p$), and ($\gamma ,2\mathrm{pn}$). The reactions ${\mathrm{Mg}}^{25}$ ${\mathrm{Mg}}^{25}(\gamma ,p){\mathrm{Na}}^{24}$ and ${\mathrm{Pb}}^{206}(\gamma ,pn){\mathrm{Tl}}^{204}$ have been established by chemical and beta-decay evidence. Weak activities were observed which could be attributed to ($\gamma ,p2n$), ($\gamma ,3\mathrm{pn}$), and ($\gamma ,\alpha n$) or ($\gamma ,2p3n$). Moderately strong activities in Al and P suggest the possibility of a nuclear process induced by quanta involving the loss of charge without change of mass.