This document discusses infrared photochemistry. It begins by defining infrared as invisible electromagnetic radiation with longer wavelengths than visible light. It then discusses how infrared lasers work and their common wavelengths. The document goes on to define photochemistry as chemical reactions induced by light absorption and discusses the laws and mechanisms of light absorption. It explains how infrared radiation is absorbed by molecules and the effects of collisions on energy transfer. The document concludes by discussing how pressure affects infrared-induced reactions and how vibrational excitation by lasers can selectively induce chemical reactions.