How does Dimmesdale punish himself in chapter 11 of The Scarlet Letter?

To relieve his guilt, Dimmesdale punishes himself in several ways. He goes without food and sleep for long periods of time, and he also whips himself on his back, causing cuts and bleeding. These attempts to atone for his sins do not work. Neither does his later standing on the scaffold at night when no one can see him. It is not until the end of the novel that Dimmesdale frees himself from guilt by confessing his sin and standing upon the scaffold with Hester and Pearl during the light of day. This is the only act that could free him.