I think the whole point of excommunication is so the person will repent and come back to the church. From the summa (sorry kinda long):
“I answer that, The judgment of the Church should be conformed to the judgment of God. Now God punishes the sinner in many ways, in order to draw him to good, either by chastising him with stripes, or by leaving him to himself so that being deprived of those helps whereby he was kept out of evil, he may acknowledge his weakness, and humbly return to God Whom he had abandoned in his pride. In both these respects the Church by passing sentence of excommunication imitates the judgment of God. For by severing a man from the communion of the faithful that he may blush with shame, she imitates the judgment whereby God chastises man with stripes; and by depriving him of prayers and other spiritual things, she imitates the judgment of God in leaving man to himself, in order that by humility he may learn to know himself and return to God.”