Gas-phase electronic spectra of polyacetylene cations: Relevance of higher excited states

Abstract

Transitions to higher electronic states of polyacetylene cations (HC 2nH+, n = 4, 5, 6) have been measured in the gas phase at 20 K. The absorption spectra were obtained using a resonant two-color, two-photon fragmentation technique in an ion trap, allowing a direct comparison between laboratory and astrophysical data. The purpose was to investigate the relevance of such transitions to astronomical observations because the general expectation is that the bands could be too broad due to fast intramolecular processes. It is shown that the origin bands are still narrow enough (1-10cm-1) to be considered, especially as the higher-lying transitions often possess large oscillator strengths. © 2010 The American Astronomical Society. All rights reserved.