Electronic Spectrum and Photodissociation Chemistry of the 1-Butyn-3-yl Cation, H3CCHCCH. J Phys Chem A 2020;124:2366-2371. [PMID: 32119779 DOI: 10.1021/acs.jpca.9b11810]

The B̃¹A' ← X̃¹A' electronic spectra of the 1-butyn-3-yl cation (H₃CCHCCH⁺) and the H₃CCHCCH⁺-Ne and H₃CCHCCH⁺-Ar complexes are measured using resonance enhanced photodissociation over the 245-285 nm range, with origin transitions occurring at 35936, 35930, and 35928 cm^-1, respectively. Vibronic bands are assigned based on quantum chemical calculations and comparison of the spectra with those of the related linear methyl propargyl (H₃C₄H₂⁺) and propargyl (H₂C₃H⁺) cations. The photofragment ions are C₂H₃⁺ (major) and C₄H₃⁺ (minor), with the preference for C₂H₃⁺ consistent with master equation simulations for a mechanism that involves rapid electronic deactivation and dissociation on the ground state potential energy surface.