Electronic spectrum and photodissociation chemistry of the linear methyl propargyl cation H2C4H3.
The electronic spectrum of the methyl propargyl cation (2-butyn-1-yl cation, H2C4H3+) is measured over the 230-270 nm range by photodissociating the bare cation and its Ar and N2tagged complexes in a tandem mass spectrometer. The observed A'1←A'1 band system has an origin at 37 753 cm-1for H2C4H3+, 37738 cm-1for H2C4H3+-Ar, and 37 658 cm-1for H2C4H3+-N2. The methyl propargyl cation photodissociates to produce either C2H3++C2H2(protonated acetylene + acetylene) or H2C4H++H2(protonated diacetylene + dihydrogen). Photodissociation spectra of H2C4H3+, H2C4H3+-Ar, and H2C4H3+-N2exhibit similar vibronic structure, with a strong progression of spacing 630 cm-1corresponding to excitation of the C-C stretch mode. Interpretation of the spectra is aided by ground and excited state calculations using time dependent density functional theory at the ωB97X-D/aug-cc-pVDZ level of theory. Ab initio calculations and master equation simulations were used to interpret the dissociation of H2C4H3+on the ground state manifold. These calculations support the experimentally observed product branching ratios in which acetylene elimination dominates and also suggests that channel switching occurs at higher energies to favor H2elimination.
School of Chemistry, The University of Melbourne, Victoria 3010, Australia.
Katherine J
KJ
Catani
School of Chemistry, The University of Melbourne, Victoria 3010, Australia.
Giel
0000000311736825
G
Muller
Department of Chemical and Biomolecular Engineering, The University of Melbourne, Victoria 3010, Australia.
Gabriel
0000000342844474
G
da Silva
School of Chemistry, The University of Melbourne, Victoria 3010, Australia.
Evan J
000000031848507X
EJ
Bieske