The C4H2+ diacetylene radical cation has been generated in a pulsed jet electrical discharge through both a diacetylene/argon mixture and an acetylene/argon mixture. The product mixture was trapped on a 12 K cryostat window and studied via Fourier transform infrared absorption spectroscopy. The diacetylene cation was also produced via low energy electron bombardment of an effusive C4H2/Ar beam. Two new infrared bands at 3201.6 and 1827.9 cm−1 have been identified as vibrations of the diacetylene cation, viz the ν4
(σu)
(C–H stretching) and the ν5(σu)
(C
C stretching) modes, respectively. Geometry optimization and harmonic frequency calculations, carried out at various spin unrestricted levels (B3LYP, CCSD(T)) for spin doublet structures, indicate that, in its electronic ground state
2Πg, the C4H2+ cation is linear. Three additional new bands at 2957.5, 1693.8 and 594.5 cm−1 have been tentatively assigned to the C–H stretching, C
C stretching and C
C–H (in-plane) bending modes, respectively, of the nonlinear diacetylene anion (C4H2–,
2Bu).
You have access to this article
Please wait while we load your content...
Something went wrong. Try again?