Abstract: Probing in-medium nucleon--nucleon (NN) cross section $\sigma^{1}_{\rm NN}(\alpha)$ in heavy ion collisions has been investigated by means of the isospin-dependent quantum molecular dynamics (IQMD) with the isospin- and momentum-dependent interaction (IMDI$(\tau)$). It is found that there are the very obvious medium effect and the sensitive isospin-dependence of nuclear stopping $R$ on the in-medium NN cross section $\sigma^{1}_{\rm NN}(\alpha)$ in the nuclear reactions induced by halo-neutron projectile and the same-mass stable projectile. However, $R$ induced by the neutron-halo projectile is obviously lower than that induced by the corresponding stable projectile. In particular, there is a very obvious dependence of $R$ on the medium effect of $\sigma^{1}_{\rm NN}(\alpha)$ in the whole beam energy region for the above two kinds of projectiles. Therefore, the comparison between the results of $R$'s in the reactions induced by the neutron-halo projectile and the corresponding same-mass stable projectile is a more favourable probe for extracting the information of $\sigma^{1}_{\rm NN}(\alpha)$ because of adding a new judgement.

Key words: isospin effect, neutron-halo projectile, nuclear reaction, nucleon-nucleon cross section, nuclear stopping