UV Raman spectroscopy was performed on a custom modified (to allow UV excitation) LabRAM HR 800 Raman System (Horiba Jobin Yvon, Bensheim, Germany) with an excitation wavelength of 244 nm provided by frequency doubling the 488 nm line of an Ar-Ion-Laser (Innova 300C Moto-FRED, Coherent Inc., Santa Clara, CA, United States of America). The laser power was attenuated from 13 mW to 5 mW or 10 mW via a neutral density filter depending on the photothermal stability of the samples. The samples were illuminated through a microscope (BX 41, Olympus Corporation, Tokyo, Japan) through a 15x/0.2NA UV objective (LMU UVB, Thorlabs Inc., Newton, NJ, United States of America) with UV optimized antireflection coating. The scattered light is collected in 180° geometry via the same objective, filtered through two long-pass filters to remove the Rayleigh scattered light, passed through an entrance slit (width = 300 µm) and diffracted by a 2400 lines/mm blazed grating to a liquid N2-cooled CCD (Top = 160 K).