EXCITATION-ENERGY DEPOSITION FROM NEUTRON MULTIPLICITY DISTRIBUTIONS FOR REACTIONS INDUCED WITH 30 A MEV N-14, NE-20, CU-63 AND 55 AMEV HE-4

Inclusive neutron multiplicity distributions have been measured for 30 A MeV N-14, Ne-20, Cu-63 and 55 A MeV He-4 beams incident on targets ranging from C-12 to U-238. For the lightest targets, the distribution s decrease approximately exponentially with increasing multiplicity. T he heavier targets display an additional Gaussian component peaked at higher multiplicities, which is attributable to central collisions. In the latter cases, the most probable multiplicities, M-n, have been e xtracted by fitting the data with a simple functional form. These mult iplicities are compared to the predictions of the statistical model co des GEMINI and CASCADE using a massive transfer scenario to define the initial conditions. Reasonable agreement is obtained for systems with estimated excitation energies approximate to 100 MeV, but the calcula tions consistently overpredict the most probable multiplicities for mo re highly excited systems. Good agreement is observed between the expe rimental M-n values and the predictions of the code EUGENE. However, this code gives M-n values that are consistently lower than those pre dicted by other statistical model calculations. An alternative procedu re is utilized to extract the amount of excitation energy of the compo site system. In this approach, the input excitation energy in a standa rd model code is varied until the predicted M-n value matches the exp erimental value. The resulting excitation energies follow systematic t rends with the estimated momentum transfer and the N/Z of the system. These patterns are also observed in reactions induced with other proje ctiles. (C) 1998 Elsevier Science B.V.