Related Experiment Video
Updated: Aug 22, 2026

Spectral and Angle-Resolved Magneto-Optical Characterization of Photonic Nanostructures
Published on: November 21, 2019
High-resolution analysis of the S1-S0 transition of magnesium phthalocyanine: Rotational structure and electronic
Yuki Miyamoto1, Katsunari Enomoto2, Kana Iwakuni3
1Research Institute for Interdisciplinary Science, Okayama University, Kita-ku, Okayama 700-8530, Japan.
Abstract:
We report a high-resolution spectroscopic analysis of the S1-S0 transition of magnesium phthalocyanine (MgPc), obtained by probing buffer-gas-cooled molecules with a narrow-linewidth laser. The observed spectrum exhibits a characteristic three-peak pattern, which is well reproduced by modeling MgPc as an oblate symmetric top with D4h symmetry. A key result of this work is that the spectrum is strongly influenced by electronic Coriolis coupling, which is associated with electronic angular momentum. The electronic Coriolis constant is determined to be ∼2, indicating an effective orbital angular momentum of about 2 in the excited S1 state, originating from the π-conjugated ring excitation. This provides a direct spectroscopic signature of electronic angular momentum in a large polyatomic molecule. The presence of nonzero electronic orbital angular momentum is qualitatively consistent with the perimeter model of phthalocyanines. The value lies within the range inferred from previous magnetic circular dichroism (MCD) studies. Compared with the previous MCD estimate, the present analysis provides a more state-specific and narrower constraint, demonstrating that high-resolution spectroscopy enables direct access to electronic and magnetic properties beyond conventional structural characterization.
Related Concept Videos
¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
NMR Spectroscopy: Chemical Shift Overview
For instance, the proton...
π Electron Effects on Chemical Shift: Aromatic and Antiaromatic Compounds
Colors and Magnetism
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
UV–Vis Spectroscopy: Molecular Electronic Transitions
π Electron Effects on Chemical Shift: Overview

