Issue 16, 2024

Gas-phase electronic spectra of HC2n+1H+ (n = 2–6) chains

Abstract

Highly unsaturated carbon chains are generated in combustion processes and electrical discharges, and are confirmed constituents of the interstellar medium. In hydrogen-rich environments smaller carbon clusters tend to exist as linear chains, capped on each end by hydrogen atoms. Although the HC2nH+ polyacetylene chains have been extensively characterized spectroscopically, the corresponding odd HC2n+1H+ chains have received far less attention. Here we use two-colour resonance enhanced photodissociation spectroscopy to measure electronic spectra for HC2n+1H+ (n = 2–6) chains contained in a cryogenically cooled quadrupole ion trap. The HC2n+1H+ chains are formed either top-down by ionizing and fragmenting pyrene molecules using pulsed 266 nm radiation, or bottom-up by reacting cyclic carbon cluster cations with acetylene. Ion mobility measurements confirm that the HC2n+1H+ species are linear, consistent with predictions from electronic structure calculations. The HC2n+1H+ electronic spectra exhibit three band systems in the visible/near infrared spectral range, which each shifts progressively to longer wavelength by ≈90 nm with the addition of each additional C[double bond, length as m-dash]C subunit. The strongest visible HC11H+ band has a wavelength (λ = 545.1 nm) and width (1.5 nm) that match the strong λ 5450 diffuse interstellar band (DIB). However, other weaker HC11H+ bands do not correspond to catalogued DIBs, casting doubt on the role of HC11H+ as a carrier for the λ 5450 DIB. There are no identifiable correspondences between catalogued DIBs and bands for the other HC2n+1H+ chains, allowing upper limits to be established for their column densities in diffuse interstellar clouds.

Graphical abstract: Gas-phase electronic spectra of HC2n+1H+ (n = 2–6) chains

Supplementary files

Article information

Article type
Paper
Submitted
12 Nah 2024
Accepted
08 Agd 2024
First published
09 Agd 2024

Phys. Chem. Chem. Phys., 2024,26, 12306-12315

Gas-phase electronic spectra of HC2n+1H+ (n = 2–6) chains

S. J. P. Marlton, C. Liu, P. Watkins and E. J. Bieske, Phys. Chem. Chem. Phys., 2024, 26, 12306 DOI: 10.1039/D4CP00625A

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements