Electronic decay process spectra including nuclear degrees of freedom

Abstract

In the field of chemistry, where nuclear motion has traditionally been a focal point, we now explore the ultra-rapid electronic motion spanning attoseconds to femtoseconds, demonstrating that it is equally integral and relevant to the discipline. The advent of ultrashort attosecond pulse technology has revolutionized our ability to directly observe electronic rearrangements in atoms and molecules, offering a time-resolved insight into these swift processes. Prominent examples include Auger-Meitner decay and Interparticle Coulombic Decay (ICD). However, the real challenge lies in interpreting these observations, where theoretical models are indispensable. Building upon the analytical framework introduced in Phys. Rev. A 101, 043414 (2020), which analyzed the spectra of electrons emitted during electronic decay processes from a purely electronic perspective, our paper represents a significant advancement. We extend this theoretical base to include nuclear dynamics, utilizing the Born-Oppenheimer approximation to deepen our understanding of the intricate interaction between electronic and nuclear motion in these processes. We illustrate the impact of incorporating nuclear degrees of freedom in several theoretical cases characterized by different numbers of vibrational bound states in both the electronic resonance and the electronic final state. This approach not only clarifies complex spectral features and unusual peak shapes but also demonstrates a method for extracting the energy differences between multiple vibrational resonance states through their distinctive interference patterns.