Ultrafast Relaxation Dynamics of Inner-Shell Vacancies in Hydrated Pyrrole

TL;DR

This work investigates ultrafast relaxation dynamics after inner-valence ionization in hydrated pyrrole by simulating coupled electronic and nuclear motion with real-space real-time TDDFT and Ehrenfest dynamics. By creating inner-valence vacancies on either the water oxygen or the pyrrole nitrogen, the study reveals vacancy-location–dependent decay pathways and charge-transfer dynamics. When the water O 2s vacancy is present, ICD dominates (~0.63) with ETMD (~0.37) within ~100 fs, accompanied by intermonomer charge transfer; with a pyrrole N 2s vacancy, ICD and Auger decay are roughly equal (~0.5 each), with Auger localized to pyrrole and minimal proton transfer observed. These findings provide microscopic insight into nonlocal energy-transfer processes in solvated biomolecular environments and have implications for understanding radiation-induced damage and designing related therapies.

Abstract

We employ real-space, real-time time-dependent density functional theory (TDDFT) combined with Ehrenfest dynamics to investigate ultrafast intermolecular relaxation following inner-valence ionization in hydrated pyrrole. This time-dependent approach treats electronic and nuclear motions simultaneously, allowing the description of electronic excitation, charge transfer, ionization, and nuclear motion.When the initial vacancy in the O 2s 1 state is created on the water molecule, the system predominantly undergoes intermolecular Coulombic decay (ICD) and electron-transfer mediated decay (ETMD), accompanied by pronounced charge transfer between pyrrole and water. In contrast, ionization of the pyrrole site for N 2s electron leads to both ICD and Auger decay channels. These results demonstrate that the decay dynamics are strongly governed by the initial vacancy location, offering microscopic insight into intermolecular energy-transfer mechanisms in hydrated molecular systems.

Figures (11)

• Figure 1: The geometric structure of the hydrated pyrrole dimer used in this study. The nuclear distance between O and N atoms is in angstroms.
• Figure 2: Time-dependent charge loss of pyrrole-water with the initial vacancy on water during the ICD process.
• Figure 3: Time-dependent electron density snapshot of pyrrole-water with the initial vacancy on water during the ICD process.
• Figure 4: Time-dependent charge loss of pyrrole-water with the initial vacancy on water during the ETMD process.
• Figure 5: Time-dependent electron density snapshot of pyrrole-water with the initial vacancy on water during the ETMD process.