A systematic experimental study of pre-compound emission in $$\alpha $$ α -particle induced reactions on odd mass nuclei A = 103–123

The compound and pre-compound emission processes have been established as two main competing de-excitation modes of an excited nucleus by-dint-of evaporation and emission of light fast particles in low energy $$\alpha $$ -induced reactions, respectively. An existence of the plenty experimental data on above established processes for a wide range of mass nuclei coerces to drive for some systematic trends in such reactions with excitation energy and mass number (A). Present work is an attempt to develop a systematics on the pre-compound emission process by analysing consistent experimental cross-section data of $$\alpha $$ -particle induced reactions on odd Z and odd A isotopic target nuclei viz., $$^{103}$$ Rh, $$^{107}$$ Ag, $$^{109}$$ Ag, $$^{113}$$ In, $$^{115}$$ In, $$^{121}$$ Sb, and $$^{123}$$ Sb, respectively. The analysis of data indicates sarcastic deviation in the experimental cross-section data with respect to calculations performed by the statistical Monte-Carlo code pace4 beyond the peak region. Such deviation becomes more prominent towards tail portion of excitation functions, which is regarded as a significant contribution of the pre-compound emission process. Observed energy dependent uniformity of such deviation for all studied reactions gives a clue for existing some systematics on concerning process with atomic mass number (A). Present study is an extension of previous work [Eur. Phys. J. A 54, 205 (2018)], but rather in more precise way for nearby isotopic target mass nuclei $$^{107}$$ Ag, $$^{109}$$ Ag, $$^{113}$$ In, $$^{115}$$ In, $$^{121}$$ Sb, and $$^{123}$$ Sb, respectively, where role of the Coulomb barrier V $$_b$$ and target deformation is found to be significantly important in the systematic decay of excited nuclei through emission of light fast particles in pre-compound process with mass number (A).