[en] Excitation functions for nuclear reactions induced by ⁴⁰Ar ions were measured for the reactions ¹⁶⁴Dy(⁴⁰Ar, xn)/sub x/Po and for the reactions ¹⁶⁰Dy(⁴⁰Ar, xn), ¹⁷⁴Yb(⁴⁰Ar, xn), and ¹⁷⁴Yb(⁴⁰Ar, pxn). For all of the systems studied, the (Ar, xn) reactions only make up a small part of the total reaction cross section of approx. 2 b; the largest cross sections encountered in each system were (at the peaks of the respective excitation functions) 30 mb for ¹⁶⁴Dy(Ar, 5n), 10 mb for ¹⁶⁰Dy(Ar, 4n), and 5 mb for ¹⁷⁴Yb(Ar, 4n--5n). The probabilities P/sub xn/ of neutron emission in the compound systems ²⁰⁴Po and ²⁰⁰Po were found to be very different, with respective maximum probabilities for the emission of four, five, and six neutrons of 0.064, 0.035, and 0.016 for ²⁰⁴Po, and 0.010, 0.0025, and 0.0003 for ²⁰⁰Po. Calculations performed with a statistical-model code, which includes angular-momentum effects and fission competition, are able to reproduce the shapes and magnitudes of the experimental excitation functions, although there is a systematic energy difference, approx. 10 MeV, between theory and the data. These model-dependent analyses describe in detail how the particle evaporation and fission deexcitation modes vary with angular momentum and excitation energy. The observed large differences in P/sub xn/ values for ²⁰⁴Po and ²⁰⁰Po are seen to arise from small difference, approx. 1.2 MeV, between the values of S/sub n/ - B/sub f/, the difference of neutron-separation and fission-barrier energies, in each compound system