Related Experiment Video
Updated: Oct 14, 2025

Photoelectron Imaging of Anions Illustrated by 310 Nm Detachment of F−
Published on: July 27, 2018
Velocity Map Imaging Spectroscopy of the Dipole-Bound State of CH2CN-: Implications for the Diffuse Interstellar
Benjamin A Laws1,2, Zachariah D Levey1, Timothy W Schmidt1
1School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia.
Abstract:
Weakly bound anionic systems present a new domain for negative ion spectroscopy. Here we report on a multifaceted study of the CH2CN- dipole-bound state, employing high-resolution photoelectron spectroscopy from 130 different wavelengths, velocity-map imaging at threshold, and laser scanning photodetachment experiments. This uncovers a wide variety of different vibrational and rotational autodetaching resonances. By examination of both sides of the problem, absorption from the anion to the dipole-bound state and vibrational/rotational autodetachment to the neutral, a complete model of the dipole-bound chemistry is formed. Precise values for the electron affinity EA = 12468.9(1) cm-1, dipole binding energy DBE = 40.2(3) cm-1, and anion inversion splitting ω5 = 115.9(2) cm-1 are obtained. This model is then employed to study possible astronomical implications, revealing good agreement between the K = 1 ← 0 CH2CN- dipole transition and the λ8040 diffuse interstellar band.
Related Concept Videos
¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR
¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
¹³C NMR: ¹H–¹³C Decoupling
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...
Spin–Spin Coupling Constant: Overview
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must...
IR Frequency Region: X–H Stretching
IR Spectrum Peak Intensity: Dipole Moment

