Dynamical emission and isotope thermometry

Abstract

Ratios of the populations of ground and excited states of ${}^{4}\mathrm{He},$ ${}^{5}\mathrm{Li},$ and ${}^{8}\mathrm{Be}$ and double ratios constructed from the yields ${}^{3,4}\mathrm{He},$ ${}^{6,7,8}\mathrm{Li},$ ${}^{11,12,13}\mathrm{C}$ isotopes were measured for central Kr+Nb collisions at $E/A=35, 70, 100,$ and 120 MeV. These ratios were analyzed to estimate an apparent temperature for emission. Consistent and approximately constant apparent temperatures were obtained from the excited states of ${}^{4}\mathrm{He},$ ${}^{5}\mathrm{Li},$ and ${}^{8}\mathrm{Be}$ nuclei and from thermometers based upon the yields of carbon isotopes. In contrast, apparent temperatures obtained from thermometers based upon the ratios using helium isotopes increase monotonically with incident energy.