The emission intensity of the 535‐nm line of a thallium‐iodide photodissociation laser excited with 193‐nm ultraviolet radiation is measured as a function of pump energy and vapor pressure. Pressure was varied between 4×10−5and 0.13 Torr. No threshold for positive gain has been found experimentally. The measurements and computer simulation indicate a possibility of constructing lasers with extremely low excitation energy.