Angle-Resolved Auger Spectroscopy as a Sensitive Access to Vibronic Coupling

Area of Science:

• Molecular spectroscopy
• Quantum chemistry
• Atomic and molecular physics

Background:

• Vibronic coupling can induce weak dipole-forbidden transitions in angle-averaged molecular spectra via excitation intensity borrowing.
• Understanding these mechanisms is crucial for interpreting complex molecular spectra.

Purpose of the Study:

• To investigate the role of vibronic coupling in angle-resolved resonant Auger decay spectra.
• To demonstrate that vibronic coupling influences both excitation and decay processes.

Main Methods:

• Complementary theoretical and experimental study.
• Resonant Auger decay spectroscopy of core-to-Rydberg excited methane (CH4) and neon (Ne).

Main Results:

• Vibronic coupling significantly impacts angle-resolved spectra, not just angle-averaged spectra.
• The decay rate borrowing mechanism, driven by vibronic coupling, is identified as crucial.
• Both excitation intensity and decay rate borrowing contribute to spectral features.

Conclusions:

• Vibronic coupling plays a decisive role in forming angle-resolved Auger decay spectra.
• Angle-resolved Auger spectroscopy is a powerful tool for probing the strength of vibronic coupling in molecules.