Final answer:
The decision to leave gives Hester and Dimmesdale a feeling of exhilaration, symbolized by changes in nature and Hester's removal of her scarlet letter, representing liberation from shame.
Step-by-step explanation:
The "exhilarating effect" that the decision to leave has on Hester and Dimmesdale in Nathaniel Hawthorne's The Scarlet Letter is an intense sensation of freedom and hope for the future, a sharp contrast to the guilt and shame they have borne. Hawthorne uses powerful symbolism to underscore this transformation, such as when the sunlight seems to shine more brightly around them, and nature itself appears to respond to their joy.
This is particularly evident as Hester removes her scarlet letter and lets down her hair, which symbolizes the shedding of her public shaming and the reclamation of her personal identity. Likewise, Dimmesdale's revitalized determination following the decision to escape with Hester indicates his temporary freedom from the torment of his hidden guilt.