Time-resolved Photo-Phonon Spectroscopy of Exchange Coupled ${Cr^{3+}}$ - Pairs in Ruby

TL;DR

This study employs time-resolved phonon detection to analyze exchange-coupled Cr^{3+} pairs in ruby, revealing energy transfer dynamics and new ion sites at cryogenic temperatures.

Contribution

It introduces a novel time-resolved bolometer method to simultaneously measure optical absorption and nonradiative transitions in ruby, providing direct observation of energy transfer in Cr^{3+} pairs.

Findings

Resonant energy transfer from single Cr ions to neighbors observed within 0.5 microseconds.

Phonon excitation spectra match known absorption spectra of Cr ions and pairs.

Identification of new perturbed Cr single-ion sites.

Abstract

A rather simple method is used to detect at once both optical absorption spectra and excited-states nonradiative transitions in 0,03 at ${%}$ and 0,16 at ${%}$ ruby at temperature 2 K. The technique utilizes a time-resolved bolometer detection of phonons, generated by the excited-state nonradiative relaxation following optical excitation with a pulsed tunable dye laser. The observed excitation spectra of phonons well coincide with already known absorption spectra of both single chromium ions and pairs of the nearest neighbors. For the first time the fast ($\leqslant 0,5 {\mu}s$)resonant energy transfer from single chromium ions to the fourth- nearest neighbors is observed directly. The new strongly perturbed $Cr$-single-ion sites are observed.