Lifetime-limited zero-phonon spectra of single molecules in methyl methacrylate

We report on high resolution single molecule spectroscopy in frozen methyl methacrylate (MMA). We show that the zero-phonon transitions of single dibenzanthanthrene molecules in this polar matrix can reach their natural linewidth limit at T = 1.4 K. Our X-ray diffraction measurements and direct study of single molecule dipole orientation provide clear evidence for the crystalline nature of MMA at low temperatures. Our results hold promise for the controlled study of the transition between crystalline and amorphous matrices, and have implications on cryogenic single molecule microscopy in biological applications.