Differential operator approach to $\imath$quantum groups and their oscillator representations

For a quasi-split Satake diagram, we define a modified $q$-Weyl algebra, and show that there is an algebra homomorphism between it and the corresponding $\imath$quantum group. In other words, we provide a differential operator approach to $\imath$quantum groups. Meanwhile, the oscillator representations of $\imath$quantum groups are obtained. The crystal basis of the irreducible subrepresentations of these oscillator representations are constructed.