The dicarbon bonding puzzle

Laws, Benjamin A.

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https://hdl.handle.net/2142/100444 Copy

Description

Title

The dicarbon bonding puzzle

Author(s)

Laws, Benjamin A.

Contributor(s)

Gibson, Stephen T.

Issue Date

2018-06-20

Keyword(s)

Small molecules

Abstract

At first glance dicarbon, C2, would appear to be a very simple homonuclear diatomic molecule. However the bonding structure of C2 has long been a topic of debate, with different qualitative theories predicting a C−C bond order of 2, 3, or even 4a . Recent evidence for a quadruply bonded dicarbon has been provided by multiconfigurational ab-initio calculationsb . However, the interpretation of these calculations has caused debate, with some research preferring the notion of a double, triple, or quasi double-triple bond, while other studies note that there is not enough evidence to clearly define the bonding nature of C2 c. In this work, photoelectron spectra of the C− 2 anion are measured using a high resolution photoelectron imaging (HR-PEI) spectrometer. The electron anisotropy of the detachment reveals the character of the parent anion orbital. Detachment to both the ground X˜ 1Σ + g and first excited a˜ 3Πu electronic states is observed, identifying the character of two orbitals: the diffuse detachment orbital of the anion, and the HOMO of the neutral. The measurements show that electron detachment occurs from a pure s-like orbital (3σg) and a dominant p-like orbital (1πu), that is inconsistent with the predictions of strongly mixed (50:50) sp orbitals required for the high bond order models, a result compatible only with the predictions of a C=C double bonding scheme.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Permalink

http://hdl.handle.net/2142/100444

DOI

10.15278/isms.2018.WH01

Copyright and License Information

Copyright 2018 Benjamin A. Laws

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