Exorcism
In Catholic Christianity, exorcisms are performed in the name of Jesus Christ. A distinction is made between a formal exorcism, which can only be conducted by a priest during a baptism or with the permission of a bishop, and "prayers of deliverance" which can be said by anyone.
The Catholic rite for a formal exorcism, called a "Major Exorcism", is given in Section 11 of the Rituale Romanum. The Ritual lists guidelines for conducting an exorcism, and for determining when a formal exorcism is required. Priests are instructed to carefully determine that the nature of the affliction is not actually a psychological or physical illness before proceeding.
Excommunication
In the Catholic Church, excommunication is normally resolved by a declaration of repentance, profession of the Creed (if the offense involved heresy) and an Act of Faith, or renewal of obedience (if that was a relevant part of the offending act, i.e., an act of schism) by the excommunicated person and the lifting of the censure (absolution) by a priest or bishop empowered to do this. "The absolution can be in the internal (private) forum only, or also in the external (public) forum, depending on whether scandal would be given if a person were privately absolved and yet publicly considered unrepentant." Since excommunication excludes from reception of the sacraments, absolution from excommunication is required before absolution can be given from the sin that led to the censure. In many cases, the whole process takes place on a single occasion in the privacy of the confessional. For some more serious wrongdoings, absolution from excommunication is reserved to a bishop, another ordinary, or even the Pope. These can delegate a priest to act on their behalf.