Observation of Z = 70 quasiatomic K x rays from 30- and 60-MeV 35Br + 35Br collisions

A K-x-ray band up to the united-atom limit for Z=70 has been observed in 30- and 60- MeV Br + Br collisions. This band can be assigned unambiguously to transitions between molecular orbitals. With a KBr target, yields at the two energies are (for Eₓ> 22 keV) 2 × 10⁻⁸ and 10⁻⁷ photons/projectile, respectively, or 10⁻⁴ photons/beam K vacancy, nearly independent of beam energy. Much reduced yields are found for Ti, Fe, and Zr targets.