Temperature Dependence of the Lifetime of 29 cm−1 Phonons in Ruby between 3 and 17 K

Abstract

By applying an optical phonon detection method (1) we measured the lifetime of 29 cm−1 phonons in ruby between 3 K and 17 K. From a blackbody spectrum of heat pulses we detect only the 29 cm−1 phonons: these are absorbed due to electronic transitions between the R1- and R2-levels of optically excited Cr3+ ions in ruby and give rise to an increase δR2 of the R2-fluorescence intensity (fig.lb). It has been shown (1,2) that for a high concentration of excited Cr3+ ions the 29 cm−1 phonons can be captured by resonant scattering in a small detector volume (fig. lc). Therefore, the decay of the δR2 signal after heat pulse injection is a measure of the lifetime of 29 cm−1 phonons.