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The energy spectra of α-particles have been measured in coincidence with the evaporation residues for the decay of the compound nucleus 31 P, produced in the reaction 19 F (96 MeV) + 12 C. The data have been compared with the predictions of the statistical model code CASCADE. It has been observed that significant deformation effect in the compound nucleus need to be considered in order to explain the shape of the evaporated α-particle energy spectra.One of the main motivations of the low energy heavy ion reactions studies has been to extract informations on the statistical properties of the hot, rotating nuclei. The informations on the main ingredients of the statistical description, i.e., the nuclear level densities and the barrier transmission probabilities, are usually obtained from the study of the evaporated light particle spectra. The validity of the statistical model depends crucially on the successful description of the light particle emission data and the model, so far, has been overwhelmingly successful in explaining a wide variety of nuclear reaction data in low energy regime. In this perspective, recent studies on the evaporated α-particle energy spectra has evoked a lot of interest (see, for example, ref.[1] and references therein). It has been observed that the standard statistical model calculations failed to predict the shape of the evaporated α-particle energy spectra satisfactorily. A large number of experiments have been performed to study this anomaly over a wide range of compound nuclear masses A CN in the range of ∼60-170 [1-6], and in all cases it has been found that the average energies of the measured α-particle energy spectra are much lower than the corresponding theoretical predictions. Several attempts have been made in the past few years to explain this anomaly. Some of the authors [2,3] argued that the discrepancy was due to the lowering of the emission barriers of the hot nuclei as compared to the fusion barriers for the corresponding relatively 'cold' inverse absorption channels as a result of the excitation energy and angular momentum dependent deformation of the emitting system in the former. On the other hand, there is another group of authors who claim that the anomaly may be well explained by incorporating spin dependent level density in the standard statistical model prescription and emission barriers need not be changed [4,5]. Moreover, it has also been observed that the magnitude of the discrepancy has some entrance channel dependence [6], the discrepancy being more for the more symmetric entrance channels. This is indicative of the fact that the magnitude of the phenomena may also be linked with the entrance channel dynamics of the system. Intuitively, the shape of the α-particle spectra would be affected by the deformation of the equilibrating system if it remains deformed over a time scale comparable to the mean life time of α emission. For heavier nuclei (A CN > 60), the theoretical calculations of shape equilibration time, using the code HICOL [1,7] show that these ti...

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Decay sequence of the hot 31 P nucleus has been investigated through exclusive light charged particle measurements using the reaction 19 F (96 MeV) + 12 C. Information on the sequential decay chain have been extracted through comparison of the experimental data with the predictions of the statistical model. It is observed from the present analysis that exclusive light charged particle data may be used as a powerful tool to probe the decay sequence of hot light compound systems.

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