Electronic spectra of C6H+ and C6H3+ in the gas phase.

Measurement of the (3)Pi-(3)Pi transition of C(6)H(+) in the gas phase near 19486 cm(-1) is reported. The experiment was carried out with a supersonic slit-jet expansion discharge using cavity ringdown absorption spectroscopy. Partly resolved P lines and observation of band heads permitted a rotational contour fit. Spectroscopic constants in the ground and excited-state were determined. The density of ions being sampled is merely 2 x 10(8) cm(-3). Broadening of the spectral lines indicates the excited-state lifetime to be approximately 100 ps. The electronic transition of HC(6)H(2)(+) at 26402 cm(-1) assumed to be (1)A(1)-X (1)A(1) in C(2v) symmetry could not be rotationally resolved. Copyright 2010 American Society for Mass Spectrometry. Published by Elsevier Inc. All rights reserved.