Velocity Map Imaging Spectroscopy of the Dipole-Bound State of CH2CN–: Implications for the Diffuse Interstellar Bands

• Published in: Journal of the American Chemical Society 2021-11, Vol.143 (44), p.18684-18692
• Main Authors: Laws, Benjamin A, Levey, Zachariah D, Schmidt, Timothy W, Gibson, Stephen T
• Format: Article
• Language: English
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.1c08762

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 D BE = 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.