This research was sponsored by the National Science Foundation Grant NSF PHY-931478

deSouza, R.T.

Fields, D.E.

Gelbke, C.K.

Kwiatkowski, K.

Lynch, W.G.

Morley, K.B.

Renshaw, E.

Tsang, M.B.

Viola, V.E.

Wile, J.L.

Yennello, S.J.

English

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NONEQUILIBRIUM SLOPE TEMPERATURES FOR IMF EMISSION IN THE 
E/A = 20-100 MeV 14N + Ig7Au REACTION 
J.L. Wile, D.E. Fields, K. Kwiatkowski, S. J. Yennello, K.B. Morley, 
E. Renshaw, R.T. deSouza, and V.E. Viola 
Indiana University Cyclotron Facility, Bloomington, Indiana 4 74 08 
C.K. Gelbke, W.G. Lynch, and M.B. Tsang 
Michigan State University, East Lansing, Michigan 48824 
Nonequilibrium slope parameters, TNEQ, have been measured for intermediate mass 
fragments formed in the 1 4 ~ +  lg7Au reaction at energies between E/A = 20 and 100 MeV. 
The values of TNEq are found to be essentially independent of IMF atomic number and 
bombarding energy above E/A = 30 MeV [Fig 1 (top)]. For natAg targets, all values 
are consistent with TNEQ = 20 MeV (except at E/A = 20 MeV, where nonequilibrium 
yields are poorly defined). Similar results have been observed by Trockel et al.,' for l6 0- 
induced reactions. Similarly, a bombarding-energy independence has been reported for 
the slope parameters associated with pion spectra from heavy-ion-induced reactions in the 
energy range E/A E 30-100 MeV, where values of T, E 20 - 22 MeV are found.2 In 
contrast, a distinct dependence of TNEQ on bombarding energy over this same energy 
range has been reported in Ref. 3 for light charged particles (LCP) and intermediate 
mass fragments (IMF) emitted in E/A = 42-151 MeV Ne- and Ar-induced reactions on 
lg7Au. The fitting procedure in Ref. 3 employed a single isotropic emission source and the 
detector configuration emphasized forward-angle IMF emission with detector thresholds 
of E/A = 3.5 MeV. To illustrate the sensitivity of TNEQ for the IMF component to 
the completeness of the data set, Fig. 1 (bottom) shows values of TNEQ for fits to our 
data performed over the angular range 30' 5 0 5 130' with detector thresholds 
for IMF's of E/A = 4 MeV, identical to those in the measurements of Ref. 3. Here one 
observes a systematic increase in TNEQ with bombarding energy, in contrast to the energy- 
independent values of TNEQ derived from the full data set. These results emphasize that 
extracted nonequilibrium temperature parameters are dependent upon the experimental 
conditions under which the data were obtained. Data taken over a limited anglar range 
or with thresholds well above Coulomb energy do not adequately account for equilibrium 
emission and thereby produce anomalous values of TNEQ. 
1. R. Trockel, K.D. Hildenbrand, U. Lynen, W.F.J. Muller, H. Rabe, et al., Prog. Part. 
Nucl. Phys. 15, 225 (1985). 
2. T. Suzuki, Proc. of Fourth Int. Conf. on Nucleus-Nuclew Collisions, ed. H. Toki and 
I. Tanihata, to be published in Nucl. Phys. 
3. B.V. Jacak, G.D. Westfall, G.M. Crawley, D. Fox, C.K. Gelbke, et al., Phys. Rev. C 
35, 1751 (1987). 
Figure 1. Values of T N E Q  for Z = 8 fragments from the 14N + lg7Au reaction as a 
function of bombarding energy. Top: fit results for angle 20" 5 O 5 160" and detector 
threshold of 8 MeV; bottom: fit results for same parameterization, but 30" 5 O < 130" 
and detector threshold of 64 MeV. 


Nonequilibrium Slope Temperatures for IMF Emission in the E/A = 20-100 MeV 14-N + 197-Au Reactions

https://scholarworks.iu.edu/dspace/bitstream/2022/613/1/iucf1991-1992_83-84.pdf

Nonequilibrium Slope Temperatures for IMF Emission in the E/A = 20-100 MeV 14-N + 197-Au Reactions

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