Infrared absorption spectroscopy of diacetylene ions trapped in solid argon.
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 v4 (sigmau) (C-H stretching) and the v5(sigmau) (C[triple bond]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 X2pi(g), 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[triple bond]C stretching and C[triple bond]C-H (in-plane) bending modes, respectively, of the nonlinear diacetylene anion (C4H2-, X2B(u)).
Department of Chemistry and Center for Chemical Physics, University of Florida, Gainesville, FL 32611-7200, USA.
Jan
J
Szczepanski
Haiyan
H
Wang
Brittnee
B
Jones
Caleb A
CA
Arrington
Martin T
MT
Vala