TY - JOUR
T1 - Wigner Near-Threshold Effects in the Photoelectron Angular Distribution of NO 2 -
AU - Laws, B. A.
AU - Cavanagh, S. J.
AU - Lewis, B. R.
AU - Gibson, S. T.
N1 - Publisher Copyright:
© 2019 American Chemical Society.
PY - 2019/12/5
Y1 - 2019/12/5
N2 - High-resolution velocity map imaged photoelectron spectra of the nitrite anion NO2- are measured over a range of photodetachment wavelengths between 355 and 550 nm, resolving the vibrational and rotational structure of the NO2(X2A1) + e- ← NO2-(X1A1) + hν transition. A full rotational band model is constructed to define the spectroscopic constants of both the neutral and the lesser studied anion ground states. The corresponding photoelectron angular distributions are characterized by a large positive anisotropy parameter, with β ≈ 1.5 gradually increasing to β ≈ 1.7 upon approaching the threshold. However, at very low kinetic energies, within 0.1 eV of the threshold, β dramatically drops to 0. This behavior is a consequence of the Wigner near-threshold selectivity of the electron partial-wave cross sections, whereby an atomic p-like orbital character adjacent to the threshold is favored. The full kinetic energy dependence of β is reproduced by a new mixed spd orbital model, yielding a NO2-(X1A1) molecular-orbital decomposition of 2% p, 44% s, and 54% d character.
AB - High-resolution velocity map imaged photoelectron spectra of the nitrite anion NO2- are measured over a range of photodetachment wavelengths between 355 and 550 nm, resolving the vibrational and rotational structure of the NO2(X2A1) + e- ← NO2-(X1A1) + hν transition. A full rotational band model is constructed to define the spectroscopic constants of both the neutral and the lesser studied anion ground states. The corresponding photoelectron angular distributions are characterized by a large positive anisotropy parameter, with β ≈ 1.5 gradually increasing to β ≈ 1.7 upon approaching the threshold. However, at very low kinetic energies, within 0.1 eV of the threshold, β dramatically drops to 0. This behavior is a consequence of the Wigner near-threshold selectivity of the electron partial-wave cross sections, whereby an atomic p-like orbital character adjacent to the threshold is favored. The full kinetic energy dependence of β is reproduced by a new mixed spd orbital model, yielding a NO2-(X1A1) molecular-orbital decomposition of 2% p, 44% s, and 54% d character.
UR - http://www.scopus.com/inward/record.url?scp=85075460435&partnerID=8YFLogxK
U2 - 10.1021/acs.jpca.9b09073
DO - 10.1021/acs.jpca.9b09073
M3 - Article
SN - 1089-5639
VL - 123
SP - 10418
EP - 10425
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
IS - 48
ER -