Final answer:
Timothy Leary was the Harvard professor who was dismissed for using LSD and wrote 'The Psychedelic Experience.'
Step-by-step explanation:
The person who was fired from Harvard for using LSD and is the author of the book "The Psychedelic Experience" is Timothy Leary. Leary was a psychologist who became well-known for his advocacy of psychedelic drugs during the 1960s. His explorations into LSD and psilocybin mushrooms, among other substances, were part of a wider counter-cultural movement that amplified discussions around consciousness, spirituality, and personal freedom.