Threshold Photoelectron Photoion Coincidence Spectroscopy of Toluene and Cycloheptatriene

Both toluene (TOL) and cycloheptatriene (CHT) molecular ions can lose a hydrogen radical to form C7H7+, which can have several possible structures, such as benzyl, tolyl, and tropylium ion. It is generally accepted that a rapid interconversion can happen between the toluene and cycloheptatriene molecular ions at threshold energy. It is also well-known that the tropylium ion is the most stable isomer of the C7H7+ ion, whereas the benzyl ion has slightly higher energy. The tropylium ion has been a matter of some debate over the last 50 years