Inelastic π+3He interaction at 100, 120 and 145MeV

π+ inelastic-scattering cross-sections on3He have been measured at 100 and 200MeV. They have been analysed together with our previously published data at 145MeV. We evidence the following features of the reaction mechanisms:a) the π+3He→π+ pd channel is dominated by the (π+ p) elastic-scattering reaction;b) the four-particle π0ppp and π+ ppn channels have a large contribution;c) the absorption cross-section values are about 5/6 of the quasi-deuteron absorption values. A comparison of our data with those obtained for other nuclei shows a rapid decrease of the absorption cross-section values for the very light nuclei. The dependence of the absorption cross-section onA is aboutA2/3 forA⩾7 and aboutA2 forA⩽4. The difference between the total and the absorption cross-section values has a smooth behaviour of the typeA2/3 for all nuclei.