Measurement of the absolute Raman scattering cross sections of sulfur and the standoff Raman detection of a 6‐mm‐thick sulfur specimen at 1500 m

The absolute Raman scattering cross sections (σRS) for the 471, 217, and 153 cm−1 modes of sulfur were measured as 6.0 ± 1.2 × 10−27, 7.7 ± 1.6 × 10−27, and 1.2 ± 0.24 × 10−26 cm2 at 815, 799, and 794 nm, respectively, using a 785‐nm pump laser. The corresponding values of σRS at 1120, 1089, and 1081 nm were determined to be 1.5 ± 0.3 × 10−27, 1.2 ± 0.24 × 10−27, and 1.2 ± 0.24 × 10−27 cm2 using a 1064‐nm laser. A temperature‐controlled, small‐cavity (2.125 mm diameter) blackbody source was used to calibrate the signal output of the Raman spectrometers for these measurements. Standoff Raman detection of a 6‐mm‐thick sulfur specimen located at 1500 m from the pump laser and the Raman spectrometer was made using a 1.4‐W, CW, 785‐nm pump laser.