We measured the phonon modes on a pentacene crystal using 4.7 mW of 633 nm excitation (He:Ne laser, ThorLabs, HNL210L). We focused the laser light onto the sample with a 60X objective. We collected the scattered light in a reflection geometry and then diffracted the laser line and Rayleigh scattering using three Bragg notch filters (OptiGrate). We averaged the spectrum for 15 seconds, and smoothed it to remove etaloning. We present the phonon mode spectrum in Figure , with corresponding frequencies and oscillation periods given in Table .