Light fragments from 14N+Ag collisions at 35 MeV/nucleon.

Abstract

Velocity spectra of thirteen different fragment species from $^{6}\mathrm{Li}$ to $^{15}\mathrm{N}$ at seven angles from 15\ifmmode^\circ\else\textdegree\fi{} to 83\ifmmode^\circ\else\textdegree\fi{} and of neutrons in coincidence with them have been determined from $^{14}\mathrm{N}$+Ag collisions at 35 MeV/nucleon. The velocity spectra of the fragments show contributions from quasielastic and deep-inelastic processes. The quasielastic part of each spectrum was fitted with an empirical model. For each fragment species, the deep-inelastic part at each of the seven angles was simultaneously fitted with a single moving source. The parameters T for source temperature and E/A, corresponding to source velocity, were approximately independent of fragment species and had average values of 12.8 and 3.9 MeV, respectively. Many coincidence neutron spectra were created off line by selecting gates having various fragment species, angles, and velocity intervals. The neutron spectra at seven or eight angles with a given gate were simultaneously fitted with two moving sources. The source parameters had little dependence on the gate. The average values of T and E/A for one source, an intermediate rapidity source, were 10.4 MeV and 10.7 MeV/nucleon, respectively. The other source, a slowly moving targetlike source, had T and E/A in the ranges 2.0--3.6 MeV and 0.1--0.3 MeV/nucleon, respectively. Since neither of these neutron sources has the velocity of the fragment source, the actual origin of the deep-inelastic fragment may be a nonequilibrium process such as the stripping-pickup process.