Laboratory gas-phase vibrational spectra of [C3H3]+ isomers and isotopologues by IRPD spectroscopy.

• Cryogenic action spectroscopy is applied to astrochemical relevant hydrocarbon ions. • Broadband vibrational gas-phase spectra of the propargyl and cyclopropenium cations are recorded with FELIX. • First spectroscopic characterization of their perdeuterated variants. • The extracted vibrational band positions allow to benchmark quantum-chemical calculations. • Isomer-selective formation pathways are investigated. Gas phase vibrational spectra of [C 3 H 3 ]+ isomers and their fully deuterated isotopologues measured in a cryogenic 22-pole ion trap are presented. The widely tunable free electron laser for infrared experiments, FELIX, was employed to cover the frequency range 500–2400 cm−1, complemented with an OPO/OPA system covering 2800–3400 cm−1. Spectral assignments for both the linear and cyclic isomeric form (H 2 C 3 H+ and c-C 3 H 3 +, respectively) are made based on various high-level computational studies. The effect of ion source conditions and different precursors (allene and propargyl chloride) for the preferential production of a specific isomer is discussed. The perturbation of the vibrational band position due to complexation with neon in the recorded infrared-predissociation (IRPD) spectra are also reported in this study. [ABSTRACT FROM AUTHOR]