Entropy produced in 35MeV/u Ar-40+Au-197 heavy ion reactions

Light charged particles emitted from the reactions of 35MeV/u Ar-40 + Au-19 7 are measured experimentally. A new observable, R = d/(d + t + He-3 + He-4 ), which is defined as the reduced yield of deuterons, has a monotone relat ion with the entropy and it is independent of the breakup density (rho/rho (0)) and N/Z of the system. The entropy values are extracted by using sever al methods which use the d/p ratios, d(like)/p(like) ratios, reduced yield of isotope deuterons R and the reduced multiplicity of charged particles M- red, respectively. The entropy values from the reduced yield of isotope deu terons R and the reduced multiplicity of charged particles Mred are nearly the same. These methods can be used in low beam energy heavy ion reactions. The charged particles emitted in rear angles are mainly from an equilibriu m-state source with temperature about 4.7 +/- 1.2MeV, which are extracted f rom the double isotope yields ratios, and entropy S/A = 2.5 +/- 0.5. This i mplies that the Break-up density is slightly less than 0.1(rho/rho (0)).