Pump-probe polarized transient hole burning (PTHB) dynamics of hydrated electron revisited

TL;DR

This study revisits femtosecond pump-probe polarized transient hole burning spectroscopy of hydrated electrons, revealing that rapid water molecule motion diminishes observable polarization signals, challenging previous assumptions about subband structures.

Contribution

The paper demonstrates that water molecule reorientation affects polarization signals in PTHB spectroscopy, explaining the lack of observed subband structures in hydrated electrons.

Findings

Rapid water reorientation diminishes polarization signals

Polarized bleach is too small and short-lived to detect

No conclusive evidence for distinct s-p subbands

Abstract

Femtosecond PTHB spectroscopy was expected to demonstrate the existence of distinct s-p absorption subbands originating from the three nondegenerate p-like excited states of hydrated electron in anisotropic solvation cavity. Yet no conclusive experimental evidence either for this subband structure or the reorientation of the cavity on the picosecond time scale has been obtained. We demonstrate that rapid reorientation of s-p transition dipole moments in response to small scale motion of water molecules is the likely culprit. The polarized bleach is shown to be too small and too short lived to be observed reliably on the sub-picosecond time scale.