Experimental excitation functions of isotopes produced in  reactions are compared with the results of empirical cross section formulas. We consider excitation functions of 16 isotopes (36Cl, 38Ar, 42,43K, 44Ti, 46,47,48Sc, 48,51Cr, 52Fe, 52,54Mn and 55,56,57Co) produced in  reactions at bombarding energies from threshold up to 2.6 GeV. They are compared with the predictions of the empirical formulas of Rudstam, Silberberg-Tsao and SPACS. In the middle-energy range, the formulas provide (in the stated order) a progressively improved description of the experimental excitation functions of the dominant isotopes. At the highest energies, the limiting values of the dominant excitation functions are well described by the EPAX formula (Version 2.1). The predictive power of these formulas could be questioned at low energies close to the threshold, reaction products with a mass much smaller than the target and possibly low cross section channels.

The production of spallation residues in 56Fe+p bombardments is described with empirical parametric formulas often used in cosmic-ray astrophysics, activation studies and isotope production for medical applications. Experimental observables including mass, charge and isotopic distributions are compared with calculations using two versions of the formulas of Rudstam and Silberberg-Tsao and the SPACS formula.  For reference, a comparison is made with the predictions of a two-stage reaction model. Deviation factors obtained in these approaches are reported.

Experimental excitation functions of isotopes produced in reactions p + natSi are compared with the results of nuclear reaction program TALYS 1.95 and semi-empirical cross section formulas. We consider excitation functions of 7 isotopes (28Mg, 26Al, 24,22Na, 18F and 10,7Be) produced in  reactions at bombarding energies of 20-144 MeV. They are compared with the predictions of the code TALYS 1.95, the semi-empirical formulas of Silberberg-Tsao (code yieldx) and SPACS. Comparisons of the results of the code TALYS 1.95 and previously published results of code ALICE are made. The predictive power of code TALYS 1.95 may be questioned for reaction products with mass number very much smaller than the target and of semi-empirical formulas at lower energies.