Revisiting the temperature dependence of the homogeneous R1 linewidth in ruby

Transient spectral-hole-burning studies of the R1(±3/2) line ( E ¯ (2E) ← 4A2(±3/2)) in 20 ppm ruby were conducted between 2.4 and 50 K in a low magnetic field (B|| = 9.15 mT) and the results were supplemented with the original data of McCumber and Sturge. A direct one-phonon process, 2 A ¯ ← E ¯ , is the main contribution to the linewidth up to 50 K whereas at higher temperatures two-phonon Raman scattering becomes dominant. The two processes are well described by Δ Γ direct = Γ 0 / ( exp ( Δ / k B T ) - 1 ) and a non-perturbative expression for the electron–phonon interaction developed by Hsu and Skinner. The value of Γ0 = 141 (±4) MHz is in excellent agreement with the result of 142 ± 6 MHz previously obtained for the R2 line.