Related Experiment Video
Updated: Jun 24, 2026
06:53
Photoelectron Imaging of Anions Illustrated by 310 Nm Detachment of F−
Published on: July 27, 2018
Electron Affinity of the Carbon Dimer from Threshold Photodetachment Spectroscopy
Sruthi Purushu Melath1, Michael Hauck1, Christine Lochmann1
1Universität Innsbruck, Institut für Ionenphysik und Angewandte Physik, Technikerstraße 25, 6020 Innsbruck, Austria.
Physical Review Letters
|June 22, 2026
Summary
This study precisely measured the electron affinity of the C2 molecule using photodetachment spectroscopy on cold trapped C2- anions. The findings confirm Wigner
Area of Science:
- Chemical Physics
- Molecular Spectroscopy
- Quantum Chemistry
Background:
- The electron affinity of the C2 molecule is crucial for understanding its chemical behavior.
- Previous measurements of C2 electron affinity have yielded conflicting results.
Purpose of the Study:
- To accurately determine the adiabatic electron affinity of C2 using photodetachment spectroscopy.
- To investigate the threshold behavior of electron detachment from C2- anions.
Main Methods:
- Photodetachment spectroscopy was performed on rotationally cold trapped C2- anions.
- Ions were prepared at cryogenic temperatures (8 K and 142 K) using a 16-pole wire trap.
- Threshold laws derived by Wigner were applied to analyze electron detachment patterns.
Main Results:
- Electron detachment exhibited p-wave and s-wave threshold behavior for transitions to the C2 X1Σg+(v′=0) and C2 a3Πu(v′=0) states, respectively.
- An accurate adiabatic electron affinity of C2 was determined to be 26364.2±0.5 cm⁻¹.
- The determined electron affinity significantly deviates from a recent photoelectron spectroscopy measurement.
Conclusions:
- The study provides a highly accurate value for the adiabatic electron affinity of C2.
- The observed threshold behavior aligns with theoretical predictions.
- Discrepancies with previous measurements highlight the need for further investigation.
Related Concept Videos
01:20¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)
When proton-coupled carbon-13 spectra are simplified by a broadband proton decoupling technique, structural information about the coupled protons is lost. Distortionless enhancement by polarization transfer (DEPT) is a technique that provides information on the number of hydrogens attached to each carbon in a molecule. While the DEPT experiment utilizes complex pulse sequences, the pulse delay and flip angle are specifically manipulated. The resulting signals have different phases depending on...
00:48¹H NMR of Labile Protons: Deuterium (²H) Substitution
This lesson illustrates the role of deuterium substitution in simplifying the NMR spectrum of compounds comprising labile protons. One method employed is the use of deuterium. Amongst the three isotopes of hydrogen, deuterium (2H) has a nucleus composed of one proton and one neutron. When the D2O solvent is added to a pure dry ethanol solution, its labile proton is substituted with deuterium.
01:10¹H NMR of Labile Protons: Temporal Resolution
Protons bonded to heteroatoms such as nitrogen and oxygen exhibit a range of chemical shift values. This is due to the varying degree of hydrogen bonding between the proton and the heteroatom in other molecules. The extent of hydrogen bonding affects the electron density around the proton, thereby giving different chemical shift values for the protons in the proton NMR spectrum.
The –OH proton in alcohols typically appears in the range of δ 2 to 5 ppm but can vary depending on the specific...
The –OH proton in alcohols typically appears in the range of δ 2 to 5 ppm but can vary depending on the specific...
01:07Proton (¹H) NMR: Chemical Shift
Organic molecules primarily contain carbon and hydrogen atoms. While all the hydrogen isotopes are NMR-active, protium or hydrogen-1 is the most abundant. It has a significant energy separation between its nuclear spin states due to its large gyromagnetic ratio. As per Boltzmann's distribution, an increase in the energy separation implies a greater excess population of nuclei available for excitation, resulting in a strong NMR absorption signal.
Absorption signals of all the protium nuclei in a...
Absorption signals of all the protium nuclei in a...
01:04¹³C NMR: ¹H–¹³C Decoupling
The probability of having two carbon-13 atoms next to each other is negligible because of the low natural abundance of carbon-13. Consequently, peak splitting due to carbon-carbon spin-spin coupling is not observed in spectra. However, protons up to three sigma bonds away split the carbon signal according to the n+1 rule, resulting in complicated spectra.
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...
01:27π Electron Effects on Chemical Shift: Overview
An applied magnetic field causes loosely bound π-electrons in organic molecules to circulate, producing a local or induced diamagnetic field over a large spatial volume. As the molecules tumble in solution, the field generated by π-electrons in spherical substituents results in a zero net field. However, the net field generated by π-electrons in non-spherical substituents is not zero. The effect of this induced field depends on the orientation of the molecule with respect to B0, resulting in...