  A compact approach based on the folding model is suggested for the
determination of the isoscalar and isovector transition strengths of the
low-lying ($\Delta S=\Delta T=0$) excitations induced by inelastic proton
scattering measured with exotic beams. Our analysis of the recently measured
inelastic $^{18,20}$O+p scattering data at $E_{\rm lab}=30$ and 43 MeV/nucleon
has given for the first time an accurate estimate of the isoscalar $\beta_0$
and isovector $\beta_1$ deformation parameters (which cannot be determined from
the (p,p') data alone by standard methods) for 2$^+_1$ and $3^-_1$ excited
states in $^{18,20}$O. Quite strong isovector mixing was found in the 2$^+_1$
inelastic $^{20}$O+p scattering channel, where the strength of the isovector
form factor $F_1$ (prototype of the Lane potential) corresponds to a $\beta_1$
value almost 3 times larger than $\beta_0$ and a ratio of nuclear transition
matrix elements $M_n/M_p\simeq 4.2$.
