Two-neutron emission from electromagnetic dissociation of ⁵⁹Co and ¹⁹⁷Au targets by relativistic heavy ions

Electromagnetic dissociation of ⁵⁹Co and ¹⁹⁷Au target nuclei and their subsequent deexcitation by two-neutron emission was observed. Beams of relativistic ¹²C, ²⁰Ne, ⁴⁰Ar, ⁵⁶Fe, and ¹³⁹La ions were used. The measured electromagnetic dissociation cross sections become large for high-Z targets and projectiles, reaching 335 mb for the ¹⁹⁷Au(¹³⁹La,X)¹⁹⁵Au reaction with 1.26 GeV/nucleon ¹³⁹La projectiles. The experimental cross sections in excess of the estimated nuclear contributions are in reasonable agreement with a calculation of the electromagnetic dissociation contribution using the Weizsäcker-Williams method for estimating the virtual photon spectrum.