Measurement of the absolute Raman cross section of the optical phonons in type Ia natural diamond

The absolute Raman cross section σ RS of the first-order 1332-cm−1 optical phonons in type Ia natural diamond was measured using 785- and 1064-nm pump lasers for the excitation of Raman scattering. A small temperature-controlled blackbody was used for the signal calibration of the 785- and 1064-nm Raman systems. Measurements were made with a 0.9-mm thick (111) natural diamond sample. Values of 2.7±0.6×10−29 and 0.95±0.2×10−29 cm2 per carbon atom were determined for σ RS for 785- and 1064-nm excitation, respectively. The corresponding values of the Raman scattering efficiency S are 3.8±0.8×10−7 and 1.3±0.3×10−7 cm−1 sr−1. The values of the Raman polarizability | d | for 785-, and 1064-nm excitation are 6.8±0.7×10−16 and 8.1±0.8×10−16 cm2, respectively. Our measured values of | d | are larger than the previously measured values of 4.4±0.3×10−16 and 4.6±0.7×10−16 cm2 using 514.5- and 694-nm excitation, respectively. | d | vs. excitation photon energy was computed for the range from 1.0 eV (1240 nm) to 4.0 eV (310 nm) using time-dependent density functional theory. The computed values of 5.8×10−16 and 5.3×10−16 cm2 for 514.4- and 694-nm excitation, respectively, are larger than the corresponding measured values of | d | . The computed values of 5.2×10−16, and 5.0×10−16 cm2 for 785- and 1064-nm excitation are smaller than the corresponding values of | d | measured in this work. The computed value of | d | in the static limit is 4.7×10−16 cm2. Modification of | d | due to IaA and IaB defects, computed for a 64-atom supercell, is less than 5%.