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

The absolute Raman cross section sigma(Rs) of the first-order 1332-cm(-1) optical phonons in type la 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 x 10(-29) and 0.95 +/- 0.2 x 10(-29) cm(2) per carbon atom were determined for sigma(Rs) for 785- and 1064-nm excitation, respectively. The corresponding values of the Raman scattering efficiency S are 3.8 +/- 0.8 x 10(-7) and 1.3 +/- 0.3 x 10(-2) cm(-1) sr(-1). The values of the Raman polarizability vertical bar d vertical bar for 785-, and 1064-nm excitation are 6.8 +/- 0.7 x 10(-16) and 8.1 +/- 0.8 x 10(-16) cm(2), respectively. Our measured values of vertical bar d vertical bar are larger than the previously measured values of 4.4 +/- 0.3 x 10(-16) and 4.6 +/- 0.7 x 10(-16) cm(2) using 514.5- and 694-nm excitation, respectively. vertical bar d vertical bar 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 x 10(-16) and 5.3 x 10(-16) cm(2) for 514.4- and 694-nm excitation, respectively, are larger than the corresponding measured values of vertical bar d vertical bar. The computed values of 5.2 x 10(-16), and 5.0 x 10(-16) cm(2) for 785- and 1064-nm excitation are smaller than the corresponding values of vertical bar d vertical bar measured in this work. The computed value of vertical bar d vertical bar in the static limit is 4.7 x 10(-16) cm(2). Modification of vertical bar d vertical bar due to IaA and IaB defects, computed for a 64-atom supercell, is less than 5%. (C) 2011 Elsevier Ltd. All rights reserved.