  The challenge of isotopic identification over a wide angular distribution has
limited the measurement of neutron-rich nuclei produced via the multinucleon
transfer (MNT) process. To investigate the optimal detection angles for the
N=126 isotones, we propose a method to construct the reasonable scattering
angles of the MNT products in the dinuclear system (DNS-sysu) model. The
reactions $^{136,144}$Xe + $^{208}$Pb are investigated. The calculated results
are in rather good agreement with the available experimental data in the
reaction $^{136}$Xe + $^{208}$Pb. The entrance channel effects on the
scattering angle are investigated. It is found that the scattering angular
distribution strongly depends on the isospin and the impact parameter of the
collision system. The optimal angle ranges for detecting $N=126$ neutron-rich
nuclides $^{204}$Pt, $^{203}$Ir, $^{202}$Os, and $^{201}$Re in the $^{136}$Xe +
$^{208}$Pb reaction at the incident energy $E_{c.m.} = 526MeV$ are predicted.
Our results suggest that the angle range $45^{\circ} \leqslant
\theta_{\mathrm{lab}} \leqslant 50^{\circ}$ is most favorable for detecting
unknown N=126 isotones. Given the current difficulties in separating and
identifying experimental MNT fragments, the results of this work could provide
significant contributions to future experiments.
