  Disentangling the isomeric structure of C7H7+ is a longstanding experimental
issue. We report here the full mid-infrared vibrational spectrum of C7H7+
tagged with Ne obtained with infrared-predissociation spectroscopy at 10 K.
Saturation depletion measurements were used to assign the contribution of
benzylium and tropylium isomers and demonstrate that no other isomer is
involved. Recorded spectral features compare well with density functional
theory calculations. This opens perspectives for a better understanding and
control of the formation paths leading to either tropylium or benzylium ions.
